Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 1 | .. highlightlang:: c |
| 2 | |
| 3 | |
| 4 | .. _initialization: |
| 5 | |
| 6 | ***************************************** |
| 7 | Initialization, Finalization, and Threads |
| 8 | ***************************************** |
| 9 | |
| 10 | |
Antoine Pitrou | 8b50b83 | 2011-01-15 11:57:42 +0000 | [diff] [blame] | 11 | Initializing and finalizing the interpreter |
| 12 | =========================================== |
| 13 | |
| 14 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 15 | .. c:function:: void Py_Initialize() |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 16 | |
| 17 | .. index:: |
| 18 | single: Py_SetProgramName() |
| 19 | single: PyEval_InitThreads() |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 20 | single: modules (in module sys) |
| 21 | single: path (in module sys) |
Georg Brandl | 1a3284e | 2007-12-02 09:40:06 +0000 | [diff] [blame] | 22 | module: builtins |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 23 | module: __main__ |
| 24 | module: sys |
| 25 | triple: module; search; path |
| 26 | single: PySys_SetArgv() |
Antoine Pitrou | f978fac | 2010-05-21 17:25:34 +0000 | [diff] [blame] | 27 | single: PySys_SetArgvEx() |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 28 | single: Py_Finalize() |
| 29 | |
| 30 | Initialize the Python interpreter. In an application embedding Python, this |
| 31 | should be called before using any other Python/C API functions; with the |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 32 | exception of :c:func:`Py_SetProgramName`, :c:func:`Py_SetPath`, |
Antoine Pitrou | f5cf435 | 2011-01-15 14:31:49 +0000 | [diff] [blame^] | 33 | and :c:func:`PyEval_InitThreads`. This initializes |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 34 | the table of loaded modules (``sys.modules``), and creates the fundamental |
Georg Brandl | 1a3284e | 2007-12-02 09:40:06 +0000 | [diff] [blame] | 35 | modules :mod:`builtins`, :mod:`__main__` and :mod:`sys`. It also initializes |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 36 | the module search path (``sys.path``). It does not set ``sys.argv``; use |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 37 | :c:func:`PySys_SetArgvEx` for that. This is a no-op when called for a second time |
| 38 | (without calling :c:func:`Py_Finalize` first). There is no return value; it is a |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 39 | fatal error if the initialization fails. |
| 40 | |
| 41 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 42 | .. c:function:: void Py_InitializeEx(int initsigs) |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 43 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 44 | This function works like :c:func:`Py_Initialize` if *initsigs* is 1. If |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 45 | *initsigs* is 0, it skips initialization registration of signal handlers, which |
| 46 | might be useful when Python is embedded. |
| 47 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 48 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 49 | .. c:function:: int Py_IsInitialized() |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 50 | |
| 51 | Return true (nonzero) when the Python interpreter has been initialized, false |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 52 | (zero) if not. After :c:func:`Py_Finalize` is called, this returns false until |
| 53 | :c:func:`Py_Initialize` is called again. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 54 | |
| 55 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 56 | .. c:function:: void Py_Finalize() |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 57 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 58 | Undo all initializations made by :c:func:`Py_Initialize` and subsequent use of |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 59 | Python/C API functions, and destroy all sub-interpreters (see |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 60 | :c:func:`Py_NewInterpreter` below) that were created and not yet destroyed since |
| 61 | the last call to :c:func:`Py_Initialize`. Ideally, this frees all memory |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 62 | allocated by the Python interpreter. This is a no-op when called for a second |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 63 | time (without calling :c:func:`Py_Initialize` again first). There is no return |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 64 | value; errors during finalization are ignored. |
| 65 | |
| 66 | This function is provided for a number of reasons. An embedding application |
| 67 | might want to restart Python without having to restart the application itself. |
| 68 | An application that has loaded the Python interpreter from a dynamically |
| 69 | loadable library (or DLL) might want to free all memory allocated by Python |
| 70 | before unloading the DLL. During a hunt for memory leaks in an application a |
| 71 | developer might want to free all memory allocated by Python before exiting from |
| 72 | the application. |
| 73 | |
| 74 | **Bugs and caveats:** The destruction of modules and objects in modules is done |
| 75 | in random order; this may cause destructors (:meth:`__del__` methods) to fail |
| 76 | when they depend on other objects (even functions) or modules. Dynamically |
| 77 | loaded extension modules loaded by Python are not unloaded. Small amounts of |
| 78 | memory allocated by the Python interpreter may not be freed (if you find a leak, |
| 79 | please report it). Memory tied up in circular references between objects is not |
| 80 | freed. Some memory allocated by extension modules may not be freed. Some |
| 81 | extensions may not work properly if their initialization routine is called more |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 82 | than once; this can happen if an application calls :c:func:`Py_Initialize` and |
| 83 | :c:func:`Py_Finalize` more than once. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 84 | |
| 85 | |
Antoine Pitrou | 8b50b83 | 2011-01-15 11:57:42 +0000 | [diff] [blame] | 86 | Process-wide parameters |
| 87 | ======================= |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 88 | |
| 89 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 90 | .. c:function:: void Py_SetProgramName(wchar_t *name) |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 91 | |
| 92 | .. index:: |
| 93 | single: Py_Initialize() |
| 94 | single: main() |
| 95 | single: Py_GetPath() |
| 96 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 97 | This function should be called before :c:func:`Py_Initialize` is called for |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 98 | the first time, if it is called at all. It tells the interpreter the value |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 99 | of the ``argv[0]`` argument to the :c:func:`main` function of the program |
Martin v. Löwis | 790465f | 2008-04-05 20:41:37 +0000 | [diff] [blame] | 100 | (converted to wide characters). |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 101 | This is used by :c:func:`Py_GetPath` and some other functions below to find |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 102 | the Python run-time libraries relative to the interpreter executable. The |
| 103 | default value is ``'python'``. The argument should point to a |
Martin v. Löwis | 790465f | 2008-04-05 20:41:37 +0000 | [diff] [blame] | 104 | zero-terminated wide character string in static storage whose contents will not |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 105 | change for the duration of the program's execution. No code in the Python |
| 106 | interpreter will change the contents of this storage. |
| 107 | |
| 108 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 109 | .. c:function:: wchar* Py_GetProgramName() |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 110 | |
| 111 | .. index:: single: Py_SetProgramName() |
| 112 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 113 | Return the program name set with :c:func:`Py_SetProgramName`, or the default. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 114 | The returned string points into static storage; the caller should not modify its |
| 115 | value. |
| 116 | |
| 117 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 118 | .. c:function:: wchar_t* Py_GetPrefix() |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 119 | |
| 120 | Return the *prefix* for installed platform-independent files. This is derived |
| 121 | through a number of complicated rules from the program name set with |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 122 | :c:func:`Py_SetProgramName` and some environment variables; for example, if the |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 123 | program name is ``'/usr/local/bin/python'``, the prefix is ``'/usr/local'``. The |
| 124 | returned string points into static storage; the caller should not modify its |
| 125 | value. This corresponds to the :makevar:`prefix` variable in the top-level |
| 126 | :file:`Makefile` and the :option:`--prefix` argument to the :program:`configure` |
| 127 | script at build time. The value is available to Python code as ``sys.prefix``. |
| 128 | It is only useful on Unix. See also the next function. |
| 129 | |
| 130 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 131 | .. c:function:: wchar_t* Py_GetExecPrefix() |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 132 | |
| 133 | Return the *exec-prefix* for installed platform-*dependent* files. This is |
| 134 | derived through a number of complicated rules from the program name set with |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 135 | :c:func:`Py_SetProgramName` and some environment variables; for example, if the |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 136 | program name is ``'/usr/local/bin/python'``, the exec-prefix is |
| 137 | ``'/usr/local'``. The returned string points into static storage; the caller |
| 138 | should not modify its value. This corresponds to the :makevar:`exec_prefix` |
| 139 | variable in the top-level :file:`Makefile` and the :option:`--exec-prefix` |
| 140 | argument to the :program:`configure` script at build time. The value is |
| 141 | available to Python code as ``sys.exec_prefix``. It is only useful on Unix. |
| 142 | |
| 143 | Background: The exec-prefix differs from the prefix when platform dependent |
| 144 | files (such as executables and shared libraries) are installed in a different |
| 145 | directory tree. In a typical installation, platform dependent files may be |
| 146 | installed in the :file:`/usr/local/plat` subtree while platform independent may |
| 147 | be installed in :file:`/usr/local`. |
| 148 | |
| 149 | Generally speaking, a platform is a combination of hardware and software |
| 150 | families, e.g. Sparc machines running the Solaris 2.x operating system are |
| 151 | considered the same platform, but Intel machines running Solaris 2.x are another |
| 152 | platform, and Intel machines running Linux are yet another platform. Different |
| 153 | major revisions of the same operating system generally also form different |
| 154 | platforms. Non-Unix operating systems are a different story; the installation |
| 155 | strategies on those systems are so different that the prefix and exec-prefix are |
| 156 | meaningless, and set to the empty string. Note that compiled Python bytecode |
| 157 | files are platform independent (but not independent from the Python version by |
| 158 | which they were compiled!). |
| 159 | |
| 160 | System administrators will know how to configure the :program:`mount` or |
| 161 | :program:`automount` programs to share :file:`/usr/local` between platforms |
| 162 | while having :file:`/usr/local/plat` be a different filesystem for each |
| 163 | platform. |
| 164 | |
| 165 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 166 | .. c:function:: wchar_t* Py_GetProgramFullPath() |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 167 | |
| 168 | .. index:: |
| 169 | single: Py_SetProgramName() |
| 170 | single: executable (in module sys) |
| 171 | |
| 172 | Return the full program name of the Python executable; this is computed as a |
| 173 | side-effect of deriving the default module search path from the program name |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 174 | (set by :c:func:`Py_SetProgramName` above). The returned string points into |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 175 | static storage; the caller should not modify its value. The value is available |
| 176 | to Python code as ``sys.executable``. |
| 177 | |
| 178 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 179 | .. c:function:: wchar_t* Py_GetPath() |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 180 | |
| 181 | .. index:: |
| 182 | triple: module; search; path |
| 183 | single: path (in module sys) |
Kristján Valur Jónsson | 3b69db2 | 2010-09-27 05:32:54 +0000 | [diff] [blame] | 184 | single: Py_SetPath() |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 185 | |
Benjamin Peterson | 46a9900 | 2010-01-09 18:45:30 +0000 | [diff] [blame] | 186 | Return the default module search path; this is computed from the program name |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 187 | (set by :c:func:`Py_SetProgramName` above) and some environment variables. |
Benjamin Peterson | 46a9900 | 2010-01-09 18:45:30 +0000 | [diff] [blame] | 188 | The returned string consists of a series of directory names separated by a |
| 189 | platform dependent delimiter character. The delimiter character is ``':'`` |
| 190 | on Unix and Mac OS X, ``';'`` on Windows. The returned string points into |
| 191 | static storage; the caller should not modify its value. The list |
| 192 | :data:`sys.path` is initialized with this value on interpreter startup; it |
| 193 | can be (and usually is) modified later to change the search path for loading |
| 194 | modules. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 195 | |
Christian Heimes | 5b5e81c | 2007-12-31 16:14:33 +0000 | [diff] [blame] | 196 | .. XXX should give the exact rules |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 197 | |
| 198 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 199 | .. c:function:: void Py_SetPath(const wchar_t *) |
Kristján Valur Jónsson | 3b69db2 | 2010-09-27 05:32:54 +0000 | [diff] [blame] | 200 | |
| 201 | .. index:: |
| 202 | triple: module; search; path |
| 203 | single: path (in module sys) |
| 204 | single: Py_GetPath() |
| 205 | |
| 206 | Set the default module search path. If this function is called before |
Georg Brandl | fa4f7f9 | 2010-10-06 10:14:08 +0000 | [diff] [blame] | 207 | :c:func:`Py_Initialize`, then :c:func:`Py_GetPath` won't attempt to compute a |
| 208 | default search path but uses the one provided instead. This is useful if |
| 209 | Python is embedded by an application that has full knowledge of the location |
| 210 | of all modules. The path components should be separated by semicolons. |
Kristján Valur Jónsson | 3b69db2 | 2010-09-27 05:32:54 +0000 | [diff] [blame] | 211 | |
Georg Brandl | fa4f7f9 | 2010-10-06 10:14:08 +0000 | [diff] [blame] | 212 | This also causes :data:`sys.executable` to be set only to the raw program |
| 213 | name (see :c:func:`Py_SetProgramName`) and for :data:`sys.prefix` and |
| 214 | :data:`sys.exec_prefix` to be empty. It is up to the caller to modify these |
| 215 | if required after calling :c:func:`Py_Initialize`. |
| 216 | |
Kristján Valur Jónsson | 3b69db2 | 2010-09-27 05:32:54 +0000 | [diff] [blame] | 217 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 218 | .. c:function:: const char* Py_GetVersion() |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 219 | |
| 220 | Return the version of this Python interpreter. This is a string that looks |
| 221 | something like :: |
| 222 | |
Georg Brandl | e6bcc91 | 2008-05-12 18:05:20 +0000 | [diff] [blame] | 223 | "3.0a5+ (py3k:63103M, May 12 2008, 00:53:55) \n[GCC 4.2.3]" |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 224 | |
| 225 | .. index:: single: version (in module sys) |
| 226 | |
| 227 | The first word (up to the first space character) is the current Python version; |
| 228 | the first three characters are the major and minor version separated by a |
| 229 | period. The returned string points into static storage; the caller should not |
Georg Brandl | e6bcc91 | 2008-05-12 18:05:20 +0000 | [diff] [blame] | 230 | modify its value. The value is available to Python code as :data:`sys.version`. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 231 | |
| 232 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 233 | .. c:function:: const char* Py_GetPlatform() |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 234 | |
| 235 | .. index:: single: platform (in module sys) |
| 236 | |
| 237 | Return the platform identifier for the current platform. On Unix, this is |
| 238 | formed from the "official" name of the operating system, converted to lower |
| 239 | case, followed by the major revision number; e.g., for Solaris 2.x, which is |
| 240 | also known as SunOS 5.x, the value is ``'sunos5'``. On Mac OS X, it is |
| 241 | ``'darwin'``. On Windows, it is ``'win'``. The returned string points into |
| 242 | static storage; the caller should not modify its value. The value is available |
| 243 | to Python code as ``sys.platform``. |
| 244 | |
| 245 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 246 | .. c:function:: const char* Py_GetCopyright() |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 247 | |
| 248 | Return the official copyright string for the current Python version, for example |
| 249 | |
| 250 | ``'Copyright 1991-1995 Stichting Mathematisch Centrum, Amsterdam'`` |
| 251 | |
| 252 | .. index:: single: copyright (in module sys) |
| 253 | |
| 254 | The returned string points into static storage; the caller should not modify its |
| 255 | value. The value is available to Python code as ``sys.copyright``. |
| 256 | |
| 257 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 258 | .. c:function:: const char* Py_GetCompiler() |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 259 | |
| 260 | Return an indication of the compiler used to build the current Python version, |
| 261 | in square brackets, for example:: |
| 262 | |
| 263 | "[GCC 2.7.2.2]" |
| 264 | |
| 265 | .. index:: single: version (in module sys) |
| 266 | |
| 267 | The returned string points into static storage; the caller should not modify its |
| 268 | value. The value is available to Python code as part of the variable |
| 269 | ``sys.version``. |
| 270 | |
| 271 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 272 | .. c:function:: const char* Py_GetBuildInfo() |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 273 | |
| 274 | Return information about the sequence number and build date and time of the |
| 275 | current Python interpreter instance, for example :: |
| 276 | |
| 277 | "#67, Aug 1 1997, 22:34:28" |
| 278 | |
| 279 | .. index:: single: version (in module sys) |
| 280 | |
| 281 | The returned string points into static storage; the caller should not modify its |
| 282 | value. The value is available to Python code as part of the variable |
| 283 | ``sys.version``. |
| 284 | |
| 285 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 286 | .. c:function:: void PySys_SetArgvEx(int argc, wchar_t **argv, int updatepath) |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 287 | |
| 288 | .. index:: |
| 289 | single: main() |
| 290 | single: Py_FatalError() |
| 291 | single: argv (in module sys) |
| 292 | |
Benjamin Peterson | 5c6d787 | 2009-02-06 02:40:07 +0000 | [diff] [blame] | 293 | Set :data:`sys.argv` based on *argc* and *argv*. These parameters are |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 294 | similar to those passed to the program's :c:func:`main` function with the |
Benjamin Peterson | 5c6d787 | 2009-02-06 02:40:07 +0000 | [diff] [blame] | 295 | difference that the first entry should refer to the script file to be |
| 296 | executed rather than the executable hosting the Python interpreter. If there |
| 297 | isn't a script that will be run, the first entry in *argv* can be an empty |
| 298 | string. If this function fails to initialize :data:`sys.argv`, a fatal |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 299 | condition is signalled using :c:func:`Py_FatalError`. |
Benjamin Peterson | 5c6d787 | 2009-02-06 02:40:07 +0000 | [diff] [blame] | 300 | |
Antoine Pitrou | f978fac | 2010-05-21 17:25:34 +0000 | [diff] [blame] | 301 | If *updatepath* is zero, this is all the function does. If *updatepath* |
| 302 | is non-zero, the function also modifies :data:`sys.path` according to the |
| 303 | following algorithm: |
| 304 | |
| 305 | - If the name of an existing script is passed in ``argv[0]``, the absolute |
| 306 | path of the directory where the script is located is prepended to |
| 307 | :data:`sys.path`. |
| 308 | - Otherwise (that is, if *argc* is 0 or ``argv[0]`` doesn't point |
| 309 | to an existing file name), an empty string is prepended to |
| 310 | :data:`sys.path`, which is the same as prepending the current working |
| 311 | directory (``"."``). |
| 312 | |
| 313 | .. note:: |
| 314 | It is recommended that applications embedding the Python interpreter |
| 315 | for purposes other than executing a single script pass 0 as *updatepath*, |
| 316 | and update :data:`sys.path` themselves if desired. |
| 317 | See `CVE-2008-5983 <http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2008-5983>`_. |
| 318 | |
| 319 | On versions before 3.1.3, you can achieve the same effect by manually |
| 320 | popping the first :data:`sys.path` element after having called |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 321 | :c:func:`PySys_SetArgv`, for example using:: |
Antoine Pitrou | f978fac | 2010-05-21 17:25:34 +0000 | [diff] [blame] | 322 | |
| 323 | PyRun_SimpleString("import sys; sys.path.pop(0)\n"); |
| 324 | |
| 325 | .. versionadded:: 3.1.3 |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 326 | |
Christian Heimes | 5b5e81c | 2007-12-31 16:14:33 +0000 | [diff] [blame] | 327 | .. XXX impl. doesn't seem consistent in allowing 0/NULL for the params; |
| 328 | check w/ Guido. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 329 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 330 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 331 | .. c:function:: void PySys_SetArgv(int argc, wchar_t **argv) |
Antoine Pitrou | f978fac | 2010-05-21 17:25:34 +0000 | [diff] [blame] | 332 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 333 | This function works like :c:func:`PySys_SetArgvEx` with *updatepath* set to 1. |
Antoine Pitrou | f978fac | 2010-05-21 17:25:34 +0000 | [diff] [blame] | 334 | |
| 335 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 336 | .. c:function:: void Py_SetPythonHome(wchar_t *home) |
Benjamin Peterson | 5c6d787 | 2009-02-06 02:40:07 +0000 | [diff] [blame] | 337 | |
| 338 | Set the default "home" directory, that is, the location of the standard |
Georg Brandl | de0ab5e | 2010-12-02 18:02:01 +0000 | [diff] [blame] | 339 | Python libraries. See :envvar:`PYTHONHOME` for the meaning of the |
| 340 | argument string. |
| 341 | |
Benjamin Peterson | 4ac9ce4 | 2009-10-04 14:49:41 +0000 | [diff] [blame] | 342 | The argument should point to a zero-terminated character string in static |
| 343 | storage whose contents will not change for the duration of the program's |
| 344 | execution. No code in the Python interpreter will change the contents of |
| 345 | this storage. |
Benjamin Peterson | 5c6d787 | 2009-02-06 02:40:07 +0000 | [diff] [blame] | 346 | |
| 347 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 348 | .. c:function:: w_char* Py_GetPythonHome() |
Benjamin Peterson | 5c6d787 | 2009-02-06 02:40:07 +0000 | [diff] [blame] | 349 | |
| 350 | Return the default "home", that is, the value set by a previous call to |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 351 | :c:func:`Py_SetPythonHome`, or the value of the :envvar:`PYTHONHOME` |
Benjamin Peterson | 5c6d787 | 2009-02-06 02:40:07 +0000 | [diff] [blame] | 352 | environment variable if it is set. |
| 353 | |
| 354 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 355 | .. _threads: |
| 356 | |
| 357 | Thread State and the Global Interpreter Lock |
| 358 | ============================================ |
| 359 | |
| 360 | .. index:: |
| 361 | single: global interpreter lock |
| 362 | single: interpreter lock |
| 363 | single: lock, interpreter |
| 364 | |
Georg Brandl | f285bcc | 2010-10-19 21:07:16 +0000 | [diff] [blame] | 365 | The Python interpreter is not fully thread-safe. In order to support |
Antoine Pitrou | bedd2c2 | 2011-01-15 12:54:19 +0000 | [diff] [blame] | 366 | multi-threaded Python programs, there's a global lock, called the :term:`global |
| 367 | interpreter lock` or :term:`GIL`, that must be held by the current thread before |
Benjamin Peterson | ef3e4c2 | 2009-04-11 19:48:14 +0000 | [diff] [blame] | 368 | it can safely access Python objects. Without the lock, even the simplest |
| 369 | operations could cause problems in a multi-threaded program: for example, when |
| 370 | two threads simultaneously increment the reference count of the same object, the |
| 371 | reference count could end up being incremented only once instead of twice. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 372 | |
Antoine Pitrou | bedd2c2 | 2011-01-15 12:54:19 +0000 | [diff] [blame] | 373 | .. index:: single: setswitchinterval() (in module sys) |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 374 | |
Antoine Pitrou | bedd2c2 | 2011-01-15 12:54:19 +0000 | [diff] [blame] | 375 | Therefore, the rule exists that only the thread that has acquired the |
| 376 | :term:`GIL` may operate on Python objects or call Python/C API functions. |
| 377 | In order to emulate concurrency of execution, the interpreter regularly |
| 378 | tries to switch threads (see :func:`sys.setswitchinterval`). The lock is also |
| 379 | released around potentially blocking I/O operations like reading or writing |
| 380 | a file, so that other Python threads can run in the meantime. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 381 | |
| 382 | .. index:: |
| 383 | single: PyThreadState |
| 384 | single: PyThreadState |
| 385 | |
Antoine Pitrou | bedd2c2 | 2011-01-15 12:54:19 +0000 | [diff] [blame] | 386 | The Python interpreter keeps some thread-specific bookkeeping information |
| 387 | inside a data structure called :c:type:`PyThreadState`. There's also one |
| 388 | global variable pointing to the current :c:type:`PyThreadState`: it can |
| 389 | be retrieved using :c:func:`PyThreadState_Get`. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 390 | |
Antoine Pitrou | bedd2c2 | 2011-01-15 12:54:19 +0000 | [diff] [blame] | 391 | Releasing the GIL from extension code |
| 392 | ------------------------------------- |
| 393 | |
| 394 | Most extension code manipulating the :term:`GIL` has the following simple |
| 395 | structure:: |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 396 | |
| 397 | Save the thread state in a local variable. |
Benjamin Peterson | ef3e4c2 | 2009-04-11 19:48:14 +0000 | [diff] [blame] | 398 | Release the global interpreter lock. |
Antoine Pitrou | bedd2c2 | 2011-01-15 12:54:19 +0000 | [diff] [blame] | 399 | ... Do some blocking I/O operation ... |
Benjamin Peterson | ef3e4c2 | 2009-04-11 19:48:14 +0000 | [diff] [blame] | 400 | Reacquire the global interpreter lock. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 401 | Restore the thread state from the local variable. |
| 402 | |
| 403 | This is so common that a pair of macros exists to simplify it:: |
| 404 | |
| 405 | Py_BEGIN_ALLOW_THREADS |
Antoine Pitrou | bedd2c2 | 2011-01-15 12:54:19 +0000 | [diff] [blame] | 406 | ... Do some blocking I/O operation ... |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 407 | Py_END_ALLOW_THREADS |
| 408 | |
| 409 | .. index:: |
| 410 | single: Py_BEGIN_ALLOW_THREADS |
| 411 | single: Py_END_ALLOW_THREADS |
| 412 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 413 | The :c:macro:`Py_BEGIN_ALLOW_THREADS` macro opens a new block and declares a |
| 414 | hidden local variable; the :c:macro:`Py_END_ALLOW_THREADS` macro closes the |
Antoine Pitrou | bedd2c2 | 2011-01-15 12:54:19 +0000 | [diff] [blame] | 415 | block. These two macros are still available when Python is compiled without |
| 416 | thread support (they simply have an empty expansion). |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 417 | |
| 418 | When thread support is enabled, the block above expands to the following code:: |
| 419 | |
| 420 | PyThreadState *_save; |
| 421 | |
| 422 | _save = PyEval_SaveThread(); |
| 423 | ...Do some blocking I/O operation... |
| 424 | PyEval_RestoreThread(_save); |
| 425 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 426 | .. index:: |
| 427 | single: PyEval_RestoreThread() |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 428 | single: PyEval_SaveThread() |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 429 | |
Antoine Pitrou | bedd2c2 | 2011-01-15 12:54:19 +0000 | [diff] [blame] | 430 | Here is how these functions work: the global interpreter lock is used to protect the pointer to the |
| 431 | current thread state. When releasing the lock and saving the thread state, |
| 432 | the current thread state pointer must be retrieved before the lock is released |
| 433 | (since another thread could immediately acquire the lock and store its own thread |
| 434 | state in the global variable). Conversely, when acquiring the lock and restoring |
| 435 | the thread state, the lock must be acquired before storing the thread state |
| 436 | pointer. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 437 | |
Antoine Pitrou | bedd2c2 | 2011-01-15 12:54:19 +0000 | [diff] [blame] | 438 | .. note:: |
| 439 | Calling system I/O functions is the most common use case for releasing |
| 440 | the GIL, but it can also be useful before calling long-running computations |
| 441 | which don't need access to Python objects, such as compression or |
| 442 | cryptographic functions operating over memory buffers. For example, the |
| 443 | standard :mod:`zlib` and :mod:`hashlib` modules release the GIL when |
| 444 | compressing or hashing data. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 445 | |
Antoine Pitrou | bedd2c2 | 2011-01-15 12:54:19 +0000 | [diff] [blame] | 446 | Non-Python created threads |
| 447 | -------------------------- |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 448 | |
Antoine Pitrou | bedd2c2 | 2011-01-15 12:54:19 +0000 | [diff] [blame] | 449 | When threads are created using the dedicated Python APIs (such as the |
| 450 | :mod:`threading` module), a thread state is automatically associated to them |
| 451 | and the code showed above is therefore correct. However, when threads are |
| 452 | created from C (for example by a third-party library with its own thread |
| 453 | management), they don't hold the GIL, nor is there a thread state structure |
| 454 | for them. |
| 455 | |
| 456 | If you need to call Python code from these threads (often this will be part |
| 457 | of a callback API provided by the aforementioned third-party library), |
| 458 | you must first register these threads with the interpreter by |
| 459 | creating a thread state data structure, then acquiring the GIL, and finally |
| 460 | storing their thread state pointer, before you can start using the Python/C |
| 461 | API. When you are done, you should reset the thread state pointer, release |
| 462 | the GIL, and finally free the thread state data structure. |
| 463 | |
| 464 | The :c:func:`PyGILState_Ensure` and :c:func:`PyGILState_Release` functions do |
| 465 | all of the above automatically. The typical idiom for calling into Python |
| 466 | from a C thread is:: |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 467 | |
| 468 | PyGILState_STATE gstate; |
| 469 | gstate = PyGILState_Ensure(); |
| 470 | |
Antoine Pitrou | bedd2c2 | 2011-01-15 12:54:19 +0000 | [diff] [blame] | 471 | /* Perform Python actions here. */ |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 472 | result = CallSomeFunction(); |
Antoine Pitrou | bedd2c2 | 2011-01-15 12:54:19 +0000 | [diff] [blame] | 473 | /* evaluate result or handle exception */ |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 474 | |
| 475 | /* Release the thread. No Python API allowed beyond this point. */ |
| 476 | PyGILState_Release(gstate); |
| 477 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 478 | Note that the :c:func:`PyGILState_\*` functions assume there is only one global |
Antoine Pitrou | bedd2c2 | 2011-01-15 12:54:19 +0000 | [diff] [blame] | 479 | interpreter (created automatically by :c:func:`Py_Initialize`). Python |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 480 | supports the creation of additional interpreters (using |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 481 | :c:func:`Py_NewInterpreter`), but mixing multiple interpreters and the |
| 482 | :c:func:`PyGILState_\*` API is unsupported. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 483 | |
Benjamin Peterson | 0df35a9 | 2009-10-04 20:32:25 +0000 | [diff] [blame] | 484 | Another important thing to note about threads is their behaviour in the face |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 485 | of the C :c:func:`fork` call. On most systems with :c:func:`fork`, after a |
Benjamin Peterson | 0df35a9 | 2009-10-04 20:32:25 +0000 | [diff] [blame] | 486 | process forks only the thread that issued the fork will exist. That also |
| 487 | means any locks held by other threads will never be released. Python solves |
| 488 | this for :func:`os.fork` by acquiring the locks it uses internally before |
| 489 | the fork, and releasing them afterwards. In addition, it resets any |
| 490 | :ref:`lock-objects` in the child. When extending or embedding Python, there |
| 491 | is no way to inform Python of additional (non-Python) locks that need to be |
| 492 | acquired before or reset after a fork. OS facilities such as |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 493 | :c:func:`posix_atfork` would need to be used to accomplish the same thing. |
| 494 | Additionally, when extending or embedding Python, calling :c:func:`fork` |
Benjamin Peterson | 0df35a9 | 2009-10-04 20:32:25 +0000 | [diff] [blame] | 495 | directly rather than through :func:`os.fork` (and returning to or calling |
| 496 | into Python) may result in a deadlock by one of Python's internal locks |
| 497 | being held by a thread that is defunct after the fork. |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 498 | :c:func:`PyOS_AfterFork` tries to reset the necessary locks, but is not |
Benjamin Peterson | 0df35a9 | 2009-10-04 20:32:25 +0000 | [diff] [blame] | 499 | always able to. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 500 | |
Antoine Pitrou | 8b50b83 | 2011-01-15 11:57:42 +0000 | [diff] [blame] | 501 | |
Antoine Pitrou | bedd2c2 | 2011-01-15 12:54:19 +0000 | [diff] [blame] | 502 | High-level API |
| 503 | -------------- |
| 504 | |
| 505 | These are the most commonly used types and functions when writing C extension |
| 506 | code, or when embedding the Python interpreter: |
| 507 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 508 | .. c:type:: PyInterpreterState |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 509 | |
| 510 | This data structure represents the state shared by a number of cooperating |
| 511 | threads. Threads belonging to the same interpreter share their module |
| 512 | administration and a few other internal items. There are no public members in |
| 513 | this structure. |
| 514 | |
| 515 | Threads belonging to different interpreters initially share nothing, except |
| 516 | process state like available memory, open file descriptors and such. The global |
| 517 | interpreter lock is also shared by all threads, regardless of to which |
| 518 | interpreter they belong. |
| 519 | |
| 520 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 521 | .. c:type:: PyThreadState |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 522 | |
| 523 | This data structure represents the state of a single thread. The only public |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 524 | data member is :c:type:`PyInterpreterState \*`:attr:`interp`, which points to |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 525 | this thread's interpreter state. |
| 526 | |
| 527 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 528 | .. c:function:: void PyEval_InitThreads() |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 529 | |
| 530 | .. index:: |
Antoine Pitrou | f5cf435 | 2011-01-15 14:31:49 +0000 | [diff] [blame^] | 531 | single: PyEval_AcquireThread() |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 532 | single: PyEval_ReleaseThread() |
| 533 | single: PyEval_SaveThread() |
| 534 | single: PyEval_RestoreThread() |
| 535 | |
| 536 | Initialize and acquire the global interpreter lock. It should be called in the |
| 537 | main thread before creating a second thread or engaging in any other thread |
Antoine Pitrou | f5cf435 | 2011-01-15 14:31:49 +0000 | [diff] [blame^] | 538 | operations such as ``PyEval_ReleaseThread(tstate)``. It is not needed before |
| 539 | calling :c:func:`PyEval_SaveThread` or :c:func:`PyEval_RestoreThread`. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 540 | |
| 541 | .. index:: single: Py_Initialize() |
| 542 | |
| 543 | This is a no-op when called for a second time. It is safe to call this function |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 544 | before calling :c:func:`Py_Initialize`. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 545 | |
Georg Brandl | 2067bfd | 2008-05-25 13:05:15 +0000 | [diff] [blame] | 546 | .. index:: module: _thread |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 547 | |
Antoine Pitrou | bedd2c2 | 2011-01-15 12:54:19 +0000 | [diff] [blame] | 548 | .. note:: |
| 549 | When only the main thread exists, no GIL operations are needed. This is a |
| 550 | common situation (most Python programs do not use threads), and the lock |
| 551 | operations slow the interpreter down a bit. Therefore, the lock is not |
| 552 | created initially. This situation is equivalent to having acquired the lock: |
| 553 | when there is only a single thread, all object accesses are safe. Therefore, |
| 554 | when this function initializes the global interpreter lock, it also acquires |
| 555 | it. Before the Python :mod:`_thread` module creates a new thread, knowing |
| 556 | that either it has the lock or the lock hasn't been created yet, it calls |
| 557 | :c:func:`PyEval_InitThreads`. When this call returns, it is guaranteed that |
| 558 | the lock has been created and that the calling thread has acquired it. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 559 | |
Antoine Pitrou | bedd2c2 | 2011-01-15 12:54:19 +0000 | [diff] [blame] | 560 | It is **not** safe to call this function when it is unknown which thread (if |
| 561 | any) currently has the global interpreter lock. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 562 | |
Antoine Pitrou | bedd2c2 | 2011-01-15 12:54:19 +0000 | [diff] [blame] | 563 | This function is not available when thread support is disabled at compile time. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 564 | |
| 565 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 566 | .. c:function:: int PyEval_ThreadsInitialized() |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 567 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 568 | Returns a non-zero value if :c:func:`PyEval_InitThreads` has been called. This |
Benjamin Peterson | ef3e4c2 | 2009-04-11 19:48:14 +0000 | [diff] [blame] | 569 | function can be called without holding the GIL, and therefore can be used to |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 570 | avoid calls to the locking API when running single-threaded. This function is |
| 571 | not available when thread support is disabled at compile time. |
| 572 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 573 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 574 | .. c:function:: PyThreadState* PyEval_SaveThread() |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 575 | |
Benjamin Peterson | ef3e4c2 | 2009-04-11 19:48:14 +0000 | [diff] [blame] | 576 | Release the global interpreter lock (if it has been created and thread |
| 577 | support is enabled) and reset the thread state to *NULL*, returning the |
| 578 | previous thread state (which is not *NULL*). If the lock has been created, |
| 579 | the current thread must have acquired it. (This function is available even |
| 580 | when thread support is disabled at compile time.) |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 581 | |
| 582 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 583 | .. c:function:: void PyEval_RestoreThread(PyThreadState *tstate) |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 584 | |
Benjamin Peterson | ef3e4c2 | 2009-04-11 19:48:14 +0000 | [diff] [blame] | 585 | Acquire the global interpreter lock (if it has been created and thread |
| 586 | support is enabled) and set the thread state to *tstate*, which must not be |
| 587 | *NULL*. If the lock has been created, the current thread must not have |
| 588 | acquired it, otherwise deadlock ensues. (This function is available even |
| 589 | when thread support is disabled at compile time.) |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 590 | |
Christian Heimes | d8654cf | 2007-12-02 15:22:16 +0000 | [diff] [blame] | 591 | |
Antoine Pitrou | bedd2c2 | 2011-01-15 12:54:19 +0000 | [diff] [blame] | 592 | .. c:function:: PyThreadState* PyThreadState_Get() |
| 593 | |
| 594 | Return the current thread state. The global interpreter lock must be held. |
| 595 | When the current thread state is *NULL*, this issues a fatal error (so that |
| 596 | the caller needn't check for *NULL*). |
| 597 | |
| 598 | |
| 599 | .. c:function:: PyThreadState* PyThreadState_Swap(PyThreadState *tstate) |
| 600 | |
| 601 | Swap the current thread state with the thread state given by the argument |
| 602 | *tstate*, which may be *NULL*. The global interpreter lock must be held |
| 603 | and is not released. |
| 604 | |
| 605 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 606 | .. c:function:: void PyEval_ReInitThreads() |
Christian Heimes | d8654cf | 2007-12-02 15:22:16 +0000 | [diff] [blame] | 607 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 608 | This function is called from :c:func:`PyOS_AfterFork` to ensure that newly |
Christian Heimes | d8654cf | 2007-12-02 15:22:16 +0000 | [diff] [blame] | 609 | created child processes don't hold locks referring to threads which |
| 610 | are not running in the child process. |
| 611 | |
| 612 | |
Antoine Pitrou | bedd2c2 | 2011-01-15 12:54:19 +0000 | [diff] [blame] | 613 | The following functions use thread-local storage, and are not compatible |
| 614 | with sub-interpreters: |
| 615 | |
| 616 | .. c:function:: PyGILState_STATE PyGILState_Ensure() |
| 617 | |
| 618 | Ensure that the current thread is ready to call the Python C API regardless |
| 619 | of the current state of Python, or of the global interpreter lock. This may |
| 620 | be called as many times as desired by a thread as long as each call is |
| 621 | matched with a call to :c:func:`PyGILState_Release`. In general, other |
| 622 | thread-related APIs may be used between :c:func:`PyGILState_Ensure` and |
| 623 | :c:func:`PyGILState_Release` calls as long as the thread state is restored to |
| 624 | its previous state before the Release(). For example, normal usage of the |
| 625 | :c:macro:`Py_BEGIN_ALLOW_THREADS` and :c:macro:`Py_END_ALLOW_THREADS` macros is |
| 626 | acceptable. |
| 627 | |
| 628 | The return value is an opaque "handle" to the thread state when |
| 629 | :c:func:`PyGILState_Ensure` was called, and must be passed to |
| 630 | :c:func:`PyGILState_Release` to ensure Python is left in the same state. Even |
| 631 | though recursive calls are allowed, these handles *cannot* be shared - each |
| 632 | unique call to :c:func:`PyGILState_Ensure` must save the handle for its call |
| 633 | to :c:func:`PyGILState_Release`. |
| 634 | |
| 635 | When the function returns, the current thread will hold the GIL and be able |
| 636 | to call arbitrary Python code. Failure is a fatal error. |
| 637 | |
| 638 | |
| 639 | .. c:function:: void PyGILState_Release(PyGILState_STATE) |
| 640 | |
| 641 | Release any resources previously acquired. After this call, Python's state will |
| 642 | be the same as it was prior to the corresponding :c:func:`PyGILState_Ensure` call |
| 643 | (but generally this state will be unknown to the caller, hence the use of the |
| 644 | GILState API). |
| 645 | |
| 646 | Every call to :c:func:`PyGILState_Ensure` must be matched by a call to |
| 647 | :c:func:`PyGILState_Release` on the same thread. |
| 648 | |
| 649 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 650 | The following macros are normally used without a trailing semicolon; look for |
| 651 | example usage in the Python source distribution. |
| 652 | |
| 653 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 654 | .. c:macro:: Py_BEGIN_ALLOW_THREADS |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 655 | |
| 656 | This macro expands to ``{ PyThreadState *_save; _save = PyEval_SaveThread();``. |
| 657 | Note that it contains an opening brace; it must be matched with a following |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 658 | :c:macro:`Py_END_ALLOW_THREADS` macro. See above for further discussion of this |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 659 | macro. It is a no-op when thread support is disabled at compile time. |
| 660 | |
| 661 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 662 | .. c:macro:: Py_END_ALLOW_THREADS |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 663 | |
| 664 | This macro expands to ``PyEval_RestoreThread(_save); }``. Note that it contains |
| 665 | a closing brace; it must be matched with an earlier |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 666 | :c:macro:`Py_BEGIN_ALLOW_THREADS` macro. See above for further discussion of |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 667 | this macro. It is a no-op when thread support is disabled at compile time. |
| 668 | |
| 669 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 670 | .. c:macro:: Py_BLOCK_THREADS |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 671 | |
| 672 | This macro expands to ``PyEval_RestoreThread(_save);``: it is equivalent to |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 673 | :c:macro:`Py_END_ALLOW_THREADS` without the closing brace. It is a no-op when |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 674 | thread support is disabled at compile time. |
| 675 | |
| 676 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 677 | .. c:macro:: Py_UNBLOCK_THREADS |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 678 | |
| 679 | This macro expands to ``_save = PyEval_SaveThread();``: it is equivalent to |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 680 | :c:macro:`Py_BEGIN_ALLOW_THREADS` without the opening brace and variable |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 681 | declaration. It is a no-op when thread support is disabled at compile time. |
| 682 | |
Antoine Pitrou | bedd2c2 | 2011-01-15 12:54:19 +0000 | [diff] [blame] | 683 | |
| 684 | Low-level API |
| 685 | ------------- |
| 686 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 687 | All of the following functions are only available when thread support is enabled |
Benjamin Peterson | ef3e4c2 | 2009-04-11 19:48:14 +0000 | [diff] [blame] | 688 | at compile time, and must be called only when the global interpreter lock has |
| 689 | been created. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 690 | |
| 691 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 692 | .. c:function:: PyInterpreterState* PyInterpreterState_New() |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 693 | |
Benjamin Peterson | ef3e4c2 | 2009-04-11 19:48:14 +0000 | [diff] [blame] | 694 | Create a new interpreter state object. The global interpreter lock need not |
| 695 | be held, but may be held if it is necessary to serialize calls to this |
| 696 | function. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 697 | |
| 698 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 699 | .. c:function:: void PyInterpreterState_Clear(PyInterpreterState *interp) |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 700 | |
Benjamin Peterson | ef3e4c2 | 2009-04-11 19:48:14 +0000 | [diff] [blame] | 701 | Reset all information in an interpreter state object. The global interpreter |
| 702 | lock must be held. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 703 | |
| 704 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 705 | .. c:function:: void PyInterpreterState_Delete(PyInterpreterState *interp) |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 706 | |
Benjamin Peterson | ef3e4c2 | 2009-04-11 19:48:14 +0000 | [diff] [blame] | 707 | Destroy an interpreter state object. The global interpreter lock need not be |
| 708 | held. The interpreter state must have been reset with a previous call to |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 709 | :c:func:`PyInterpreterState_Clear`. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 710 | |
| 711 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 712 | .. c:function:: PyThreadState* PyThreadState_New(PyInterpreterState *interp) |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 713 | |
Benjamin Peterson | ef3e4c2 | 2009-04-11 19:48:14 +0000 | [diff] [blame] | 714 | Create a new thread state object belonging to the given interpreter object. |
| 715 | The global interpreter lock need not be held, but may be held if it is |
| 716 | necessary to serialize calls to this function. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 717 | |
| 718 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 719 | .. c:function:: void PyThreadState_Clear(PyThreadState *tstate) |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 720 | |
Benjamin Peterson | ef3e4c2 | 2009-04-11 19:48:14 +0000 | [diff] [blame] | 721 | Reset all information in a thread state object. The global interpreter lock |
| 722 | must be held. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 723 | |
| 724 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 725 | .. c:function:: void PyThreadState_Delete(PyThreadState *tstate) |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 726 | |
Benjamin Peterson | ef3e4c2 | 2009-04-11 19:48:14 +0000 | [diff] [blame] | 727 | Destroy a thread state object. The global interpreter lock need not be held. |
| 728 | The thread state must have been reset with a previous call to |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 729 | :c:func:`PyThreadState_Clear`. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 730 | |
| 731 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 732 | .. c:function:: PyObject* PyThreadState_GetDict() |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 733 | |
| 734 | Return a dictionary in which extensions can store thread-specific state |
| 735 | information. Each extension should use a unique key to use to store state in |
| 736 | the dictionary. It is okay to call this function when no current thread state |
| 737 | is available. If this function returns *NULL*, no exception has been raised and |
| 738 | the caller should assume no current thread state is available. |
| 739 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 740 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 741 | .. c:function:: int PyThreadState_SetAsyncExc(long id, PyObject *exc) |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 742 | |
| 743 | Asynchronously raise an exception in a thread. The *id* argument is the thread |
| 744 | id of the target thread; *exc* is the exception object to be raised. This |
| 745 | function does not steal any references to *exc*. To prevent naive misuse, you |
| 746 | must write your own C extension to call this. Must be called with the GIL held. |
| 747 | Returns the number of thread states modified; this is normally one, but will be |
| 748 | zero if the thread id isn't found. If *exc* is :const:`NULL`, the pending |
| 749 | exception (if any) for the thread is cleared. This raises no exceptions. |
| 750 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 751 | |
Antoine Pitrou | bedd2c2 | 2011-01-15 12:54:19 +0000 | [diff] [blame] | 752 | .. c:function:: void PyEval_AcquireThread(PyThreadState *tstate) |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 753 | |
Antoine Pitrou | bedd2c2 | 2011-01-15 12:54:19 +0000 | [diff] [blame] | 754 | Acquire the global interpreter lock and set the current thread state to |
| 755 | *tstate*, which should not be *NULL*. The lock must have been created earlier. |
| 756 | If this thread already has the lock, deadlock ensues. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 757 | |
Antoine Pitrou | 5ace8e9 | 2011-01-15 13:11:48 +0000 | [diff] [blame] | 758 | :c:func:`PyEval_RestoreThread` is a higher-level function which is always |
| 759 | available (even when thread support isn't enabled or when threads have |
| 760 | not been initialized). |
| 761 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 762 | |
Antoine Pitrou | bedd2c2 | 2011-01-15 12:54:19 +0000 | [diff] [blame] | 763 | .. c:function:: void PyEval_ReleaseThread(PyThreadState *tstate) |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 764 | |
Antoine Pitrou | bedd2c2 | 2011-01-15 12:54:19 +0000 | [diff] [blame] | 765 | Reset the current thread state to *NULL* and release the global interpreter |
| 766 | lock. The lock must have been created earlier and must be held by the current |
| 767 | thread. The *tstate* argument, which must not be *NULL*, is only used to check |
| 768 | that it represents the current thread state --- if it isn't, a fatal error is |
| 769 | reported. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 770 | |
Antoine Pitrou | 5ace8e9 | 2011-01-15 13:11:48 +0000 | [diff] [blame] | 771 | :c:func:`PyEval_SaveThread` is a higher-level function which is always |
| 772 | available (even when thread support isn't enabled or when threads have |
| 773 | not been initialized). |
| 774 | |
Antoine Pitrou | bedd2c2 | 2011-01-15 12:54:19 +0000 | [diff] [blame] | 775 | |
| 776 | .. c:function:: void PyEval_AcquireLock() |
| 777 | |
| 778 | Acquire the global interpreter lock. The lock must have been created earlier. |
| 779 | If this thread already has the lock, a deadlock ensues. |
| 780 | |
Antoine Pitrou | 5ace8e9 | 2011-01-15 13:11:48 +0000 | [diff] [blame] | 781 | .. deprecated:: 3.2 |
Antoine Pitrou | f5cf435 | 2011-01-15 14:31:49 +0000 | [diff] [blame^] | 782 | This function does not update the current thread state. Please use |
Antoine Pitrou | 5ace8e9 | 2011-01-15 13:11:48 +0000 | [diff] [blame] | 783 | :c:func:`PyEval_RestoreThread` or :c:func:`PyEval_AcquireThread` |
| 784 | instead. |
| 785 | |
Antoine Pitrou | bedd2c2 | 2011-01-15 12:54:19 +0000 | [diff] [blame] | 786 | |
| 787 | .. c:function:: void PyEval_ReleaseLock() |
| 788 | |
| 789 | Release the global interpreter lock. The lock must have been created earlier. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 790 | |
Antoine Pitrou | 5ace8e9 | 2011-01-15 13:11:48 +0000 | [diff] [blame] | 791 | .. deprecated:: 3.2 |
Antoine Pitrou | f5cf435 | 2011-01-15 14:31:49 +0000 | [diff] [blame^] | 792 | This function does not update the current thread state. Please use |
Antoine Pitrou | 5ace8e9 | 2011-01-15 13:11:48 +0000 | [diff] [blame] | 793 | :c:func:`PyEval_SaveThread` or :c:func:`PyEval_ReleaseThread` |
| 794 | instead. |
| 795 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 796 | |
Antoine Pitrou | 8b50b83 | 2011-01-15 11:57:42 +0000 | [diff] [blame] | 797 | Sub-interpreter support |
| 798 | ======================= |
| 799 | |
| 800 | While in most uses, you will only embed a single Python interpreter, there |
| 801 | are cases where you need to create several independent interpreters in the |
| 802 | same process and perhaps even in the same thread. Sub-interpreters allow |
Antoine Pitrou | 9bf8d1c | 2011-01-15 12:21:53 +0000 | [diff] [blame] | 803 | you to do that. You can switch between sub-interpreters using the |
| 804 | :c:func:`PyThreadState_Swap` function. You can create and destroy them |
| 805 | using the following functions: |
Antoine Pitrou | 8b50b83 | 2011-01-15 11:57:42 +0000 | [diff] [blame] | 806 | |
| 807 | |
| 808 | .. c:function:: PyThreadState* Py_NewInterpreter() |
| 809 | |
| 810 | .. index:: |
| 811 | module: builtins |
| 812 | module: __main__ |
| 813 | module: sys |
| 814 | single: stdout (in module sys) |
| 815 | single: stderr (in module sys) |
| 816 | single: stdin (in module sys) |
| 817 | |
| 818 | Create a new sub-interpreter. This is an (almost) totally separate environment |
| 819 | for the execution of Python code. In particular, the new interpreter has |
| 820 | separate, independent versions of all imported modules, including the |
| 821 | fundamental modules :mod:`builtins`, :mod:`__main__` and :mod:`sys`. The |
| 822 | table of loaded modules (``sys.modules``) and the module search path |
| 823 | (``sys.path``) are also separate. The new environment has no ``sys.argv`` |
| 824 | variable. It has new standard I/O stream file objects ``sys.stdin``, |
| 825 | ``sys.stdout`` and ``sys.stderr`` (however these refer to the same underlying |
| 826 | file descriptors). |
| 827 | |
| 828 | The return value points to the first thread state created in the new |
| 829 | sub-interpreter. This thread state is made in the current thread state. |
| 830 | Note that no actual thread is created; see the discussion of thread states |
| 831 | below. If creation of the new interpreter is unsuccessful, *NULL* is |
| 832 | returned; no exception is set since the exception state is stored in the |
| 833 | current thread state and there may not be a current thread state. (Like all |
| 834 | other Python/C API functions, the global interpreter lock must be held before |
| 835 | calling this function and is still held when it returns; however, unlike most |
| 836 | other Python/C API functions, there needn't be a current thread state on |
| 837 | entry.) |
| 838 | |
| 839 | .. index:: |
| 840 | single: Py_Finalize() |
| 841 | single: Py_Initialize() |
| 842 | |
| 843 | Extension modules are shared between (sub-)interpreters as follows: the first |
| 844 | time a particular extension is imported, it is initialized normally, and a |
| 845 | (shallow) copy of its module's dictionary is squirreled away. When the same |
| 846 | extension is imported by another (sub-)interpreter, a new module is initialized |
| 847 | and filled with the contents of this copy; the extension's ``init`` function is |
| 848 | not called. Note that this is different from what happens when an extension is |
| 849 | imported after the interpreter has been completely re-initialized by calling |
| 850 | :c:func:`Py_Finalize` and :c:func:`Py_Initialize`; in that case, the extension's |
| 851 | ``initmodule`` function *is* called again. |
| 852 | |
| 853 | .. index:: single: close() (in module os) |
| 854 | |
| 855 | |
| 856 | .. c:function:: void Py_EndInterpreter(PyThreadState *tstate) |
| 857 | |
| 858 | .. index:: single: Py_Finalize() |
| 859 | |
| 860 | Destroy the (sub-)interpreter represented by the given thread state. The given |
| 861 | thread state must be the current thread state. See the discussion of thread |
| 862 | states below. When the call returns, the current thread state is *NULL*. All |
| 863 | thread states associated with this interpreter are destroyed. (The global |
| 864 | interpreter lock must be held before calling this function and is still held |
| 865 | when it returns.) :c:func:`Py_Finalize` will destroy all sub-interpreters that |
| 866 | haven't been explicitly destroyed at that point. |
| 867 | |
| 868 | |
| 869 | Bugs and caveats |
| 870 | ---------------- |
| 871 | |
| 872 | Because sub-interpreters (and the main interpreter) are part of the same |
| 873 | process, the insulation between them isn't perfect --- for example, using |
| 874 | low-level file operations like :func:`os.close` they can |
| 875 | (accidentally or maliciously) affect each other's open files. Because of the |
| 876 | way extensions are shared between (sub-)interpreters, some extensions may not |
| 877 | work properly; this is especially likely when the extension makes use of |
| 878 | (static) global variables, or when the extension manipulates its module's |
| 879 | dictionary after its initialization. It is possible to insert objects created |
| 880 | in one sub-interpreter into a namespace of another sub-interpreter; this should |
| 881 | be done with great care to avoid sharing user-defined functions, methods, |
| 882 | instances or classes between sub-interpreters, since import operations executed |
| 883 | by such objects may affect the wrong (sub-)interpreter's dictionary of loaded |
Antoine Pitrou | f1dfe73 | 2011-01-15 12:10:48 +0000 | [diff] [blame] | 884 | modules. |
Antoine Pitrou | 8b50b83 | 2011-01-15 11:57:42 +0000 | [diff] [blame] | 885 | |
Antoine Pitrou | f1dfe73 | 2011-01-15 12:10:48 +0000 | [diff] [blame] | 886 | Also note that combining this functionality with :c:func:`PyGILState_\*` APIs |
| 887 | is delicate, become these APIs assume a bijection between Python thread states |
| 888 | and OS-level threads, an assumption broken by the presence of sub-interpreters. |
| 889 | It is highly recommended that you don't switch sub-interpreters between a pair |
| 890 | of matching :c:func:`PyGILState_Ensure` and :c:func:`PyGILState_Release` calls. |
| 891 | Furthermore, extensions (such as :mod:`ctypes`) using these APIs to allow calling |
| 892 | of Python code from non-Python created threads will probably be broken when using |
| 893 | sub-interpreters. |
Antoine Pitrou | 8b50b83 | 2011-01-15 11:57:42 +0000 | [diff] [blame] | 894 | |
Benjamin Peterson | a54c909 | 2009-01-13 02:11:23 +0000 | [diff] [blame] | 895 | |
| 896 | Asynchronous Notifications |
| 897 | ========================== |
| 898 | |
Benjamin Peterson | d23f822 | 2009-04-05 19:13:16 +0000 | [diff] [blame] | 899 | A mechanism is provided to make asynchronous notifications to the main |
Benjamin Peterson | a54c909 | 2009-01-13 02:11:23 +0000 | [diff] [blame] | 900 | interpreter thread. These notifications take the form of a function |
| 901 | pointer and a void argument. |
| 902 | |
| 903 | .. index:: single: setcheckinterval() (in module sys) |
| 904 | |
Benjamin Peterson | ef3e4c2 | 2009-04-11 19:48:14 +0000 | [diff] [blame] | 905 | Every check interval, when the global interpreter lock is released and |
Ezio Melotti | 0639d5a | 2009-12-19 23:26:38 +0000 | [diff] [blame] | 906 | reacquired, Python will also call any such provided functions. This can be used |
Benjamin Peterson | ef3e4c2 | 2009-04-11 19:48:14 +0000 | [diff] [blame] | 907 | for example by asynchronous IO handlers. The notification can be scheduled from |
| 908 | a worker thread and the actual call than made at the earliest convenience by the |
| 909 | main thread where it has possession of the global interpreter lock and can |
| 910 | perform any Python API calls. |
Benjamin Peterson | a54c909 | 2009-01-13 02:11:23 +0000 | [diff] [blame] | 911 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 912 | .. c:function:: void Py_AddPendingCall( int (*func)(void *, void *arg) ) |
Benjamin Peterson | a54c909 | 2009-01-13 02:11:23 +0000 | [diff] [blame] | 913 | |
| 914 | .. index:: single: Py_AddPendingCall() |
| 915 | |
Benjamin Peterson | ef3e4c2 | 2009-04-11 19:48:14 +0000 | [diff] [blame] | 916 | Post a notification to the Python main thread. If successful, *func* will be |
| 917 | called with the argument *arg* at the earliest convenience. *func* will be |
| 918 | called having the global interpreter lock held and can thus use the full |
| 919 | Python API and can take any action such as setting object attributes to |
| 920 | signal IO completion. It must return 0 on success, or -1 signalling an |
| 921 | exception. The notification function won't be interrupted to perform another |
| 922 | asynchronous notification recursively, but it can still be interrupted to |
| 923 | switch threads if the global interpreter lock is released, for example, if it |
Ezio Melotti | 0639d5a | 2009-12-19 23:26:38 +0000 | [diff] [blame] | 924 | calls back into Python code. |
Benjamin Peterson | a54c909 | 2009-01-13 02:11:23 +0000 | [diff] [blame] | 925 | |
| 926 | This function returns 0 on success in which case the notification has been |
Benjamin Peterson | ef3e4c2 | 2009-04-11 19:48:14 +0000 | [diff] [blame] | 927 | scheduled. Otherwise, for example if the notification buffer is full, it |
| 928 | returns -1 without setting any exception. |
Benjamin Peterson | a54c909 | 2009-01-13 02:11:23 +0000 | [diff] [blame] | 929 | |
Benjamin Peterson | ef3e4c2 | 2009-04-11 19:48:14 +0000 | [diff] [blame] | 930 | This function can be called on any thread, be it a Python thread or some |
| 931 | other system thread. If it is a Python thread, it doesn't matter if it holds |
| 932 | the global interpreter lock or not. |
Benjamin Peterson | a54c909 | 2009-01-13 02:11:23 +0000 | [diff] [blame] | 933 | |
Georg Brandl | 705d9d5 | 2009-05-05 09:29:50 +0000 | [diff] [blame] | 934 | .. versionadded:: 3.1 |
Benjamin Peterson | a54c909 | 2009-01-13 02:11:23 +0000 | [diff] [blame] | 935 | |
| 936 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 937 | .. _profiling: |
| 938 | |
| 939 | Profiling and Tracing |
| 940 | ===================== |
| 941 | |
| 942 | .. sectionauthor:: Fred L. Drake, Jr. <fdrake@acm.org> |
| 943 | |
| 944 | |
| 945 | The Python interpreter provides some low-level support for attaching profiling |
| 946 | and execution tracing facilities. These are used for profiling, debugging, and |
| 947 | coverage analysis tools. |
| 948 | |
Georg Brandl | e6bcc91 | 2008-05-12 18:05:20 +0000 | [diff] [blame] | 949 | This C interface allows the profiling or tracing code to avoid the overhead of |
| 950 | calling through Python-level callable objects, making a direct C function call |
| 951 | instead. The essential attributes of the facility have not changed; the |
| 952 | interface allows trace functions to be installed per-thread, and the basic |
| 953 | events reported to the trace function are the same as had been reported to the |
| 954 | Python-level trace functions in previous versions. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 955 | |
| 956 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 957 | .. c:type:: int (*Py_tracefunc)(PyObject *obj, PyFrameObject *frame, int what, PyObject *arg) |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 958 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 959 | The type of the trace function registered using :c:func:`PyEval_SetProfile` and |
| 960 | :c:func:`PyEval_SetTrace`. The first parameter is the object passed to the |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 961 | registration function as *obj*, *frame* is the frame object to which the event |
| 962 | pertains, *what* is one of the constants :const:`PyTrace_CALL`, |
| 963 | :const:`PyTrace_EXCEPTION`, :const:`PyTrace_LINE`, :const:`PyTrace_RETURN`, |
| 964 | :const:`PyTrace_C_CALL`, :const:`PyTrace_C_EXCEPTION`, or |
| 965 | :const:`PyTrace_C_RETURN`, and *arg* depends on the value of *what*: |
| 966 | |
| 967 | +------------------------------+--------------------------------------+ |
| 968 | | Value of *what* | Meaning of *arg* | |
| 969 | +==============================+======================================+ |
| 970 | | :const:`PyTrace_CALL` | Always *NULL*. | |
| 971 | +------------------------------+--------------------------------------+ |
| 972 | | :const:`PyTrace_EXCEPTION` | Exception information as returned by | |
| 973 | | | :func:`sys.exc_info`. | |
| 974 | +------------------------------+--------------------------------------+ |
| 975 | | :const:`PyTrace_LINE` | Always *NULL*. | |
| 976 | +------------------------------+--------------------------------------+ |
Georg Brandl | d0b0e1d | 2010-10-15 16:42:37 +0000 | [diff] [blame] | 977 | | :const:`PyTrace_RETURN` | Value being returned to the caller, | |
| 978 | | | or *NULL* if caused by an exception. | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 979 | +------------------------------+--------------------------------------+ |
Georg Brandl | d0b0e1d | 2010-10-15 16:42:37 +0000 | [diff] [blame] | 980 | | :const:`PyTrace_C_CALL` | Function object being called. | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 981 | +------------------------------+--------------------------------------+ |
Georg Brandl | d0b0e1d | 2010-10-15 16:42:37 +0000 | [diff] [blame] | 982 | | :const:`PyTrace_C_EXCEPTION` | Function object being called. | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 983 | +------------------------------+--------------------------------------+ |
Georg Brandl | d0b0e1d | 2010-10-15 16:42:37 +0000 | [diff] [blame] | 984 | | :const:`PyTrace_C_RETURN` | Function object being called. | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 985 | +------------------------------+--------------------------------------+ |
| 986 | |
| 987 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 988 | .. c:var:: int PyTrace_CALL |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 989 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 990 | The value of the *what* parameter to a :c:type:`Py_tracefunc` function when a new |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 991 | call to a function or method is being reported, or a new entry into a generator. |
| 992 | Note that the creation of the iterator for a generator function is not reported |
| 993 | as there is no control transfer to the Python bytecode in the corresponding |
| 994 | frame. |
| 995 | |
| 996 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 997 | .. c:var:: int PyTrace_EXCEPTION |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 998 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 999 | The value of the *what* parameter to a :c:type:`Py_tracefunc` function when an |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 1000 | exception has been raised. The callback function is called with this value for |
| 1001 | *what* when after any bytecode is processed after which the exception becomes |
| 1002 | set within the frame being executed. The effect of this is that as exception |
| 1003 | propagation causes the Python stack to unwind, the callback is called upon |
| 1004 | return to each frame as the exception propagates. Only trace functions receives |
| 1005 | these events; they are not needed by the profiler. |
| 1006 | |
| 1007 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 1008 | .. c:var:: int PyTrace_LINE |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 1009 | |
| 1010 | The value passed as the *what* parameter to a trace function (but not a |
| 1011 | profiling function) when a line-number event is being reported. |
| 1012 | |
| 1013 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 1014 | .. c:var:: int PyTrace_RETURN |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 1015 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 1016 | The value for the *what* parameter to :c:type:`Py_tracefunc` functions when a |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 1017 | call is returning without propagating an exception. |
| 1018 | |
| 1019 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 1020 | .. c:var:: int PyTrace_C_CALL |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 1021 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 1022 | The value for the *what* parameter to :c:type:`Py_tracefunc` functions when a C |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 1023 | function is about to be called. |
| 1024 | |
| 1025 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 1026 | .. c:var:: int PyTrace_C_EXCEPTION |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 1027 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 1028 | The value for the *what* parameter to :c:type:`Py_tracefunc` functions when a C |
Georg Brandl | 7cb1319 | 2010-08-03 12:06:29 +0000 | [diff] [blame] | 1029 | function has raised an exception. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 1030 | |
| 1031 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 1032 | .. c:var:: int PyTrace_C_RETURN |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 1033 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 1034 | The value for the *what* parameter to :c:type:`Py_tracefunc` functions when a C |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 1035 | function has returned. |
| 1036 | |
| 1037 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 1038 | .. c:function:: void PyEval_SetProfile(Py_tracefunc func, PyObject *obj) |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 1039 | |
| 1040 | Set the profiler function to *func*. The *obj* parameter is passed to the |
| 1041 | function as its first parameter, and may be any Python object, or *NULL*. If |
| 1042 | the profile function needs to maintain state, using a different value for *obj* |
| 1043 | for each thread provides a convenient and thread-safe place to store it. The |
| 1044 | profile function is called for all monitored events except the line-number |
| 1045 | events. |
| 1046 | |
| 1047 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 1048 | .. c:function:: void PyEval_SetTrace(Py_tracefunc func, PyObject *obj) |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 1049 | |
| 1050 | Set the tracing function to *func*. This is similar to |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 1051 | :c:func:`PyEval_SetProfile`, except the tracing function does receive line-number |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 1052 | events. |
| 1053 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 1054 | .. c:function:: PyObject* PyEval_GetCallStats(PyObject *self) |
Christian Heimes | d8654cf | 2007-12-02 15:22:16 +0000 | [diff] [blame] | 1055 | |
| 1056 | Return a tuple of function call counts. There are constants defined for the |
| 1057 | positions within the tuple: |
Georg Brandl | 48310cd | 2009-01-03 21:18:54 +0000 | [diff] [blame] | 1058 | |
Christian Heimes | d8654cf | 2007-12-02 15:22:16 +0000 | [diff] [blame] | 1059 | +-------------------------------+-------+ |
| 1060 | | Name | Value | |
| 1061 | +===============================+=======+ |
| 1062 | | :const:`PCALL_ALL` | 0 | |
| 1063 | +-------------------------------+-------+ |
| 1064 | | :const:`PCALL_FUNCTION` | 1 | |
| 1065 | +-------------------------------+-------+ |
| 1066 | | :const:`PCALL_FAST_FUNCTION` | 2 | |
| 1067 | +-------------------------------+-------+ |
| 1068 | | :const:`PCALL_FASTER_FUNCTION`| 3 | |
| 1069 | +-------------------------------+-------+ |
| 1070 | | :const:`PCALL_METHOD` | 4 | |
| 1071 | +-------------------------------+-------+ |
| 1072 | | :const:`PCALL_BOUND_METHOD` | 5 | |
| 1073 | +-------------------------------+-------+ |
| 1074 | | :const:`PCALL_CFUNCTION` | 6 | |
| 1075 | +-------------------------------+-------+ |
| 1076 | | :const:`PCALL_TYPE` | 7 | |
| 1077 | +-------------------------------+-------+ |
| 1078 | | :const:`PCALL_GENERATOR` | 8 | |
| 1079 | +-------------------------------+-------+ |
| 1080 | | :const:`PCALL_OTHER` | 9 | |
| 1081 | +-------------------------------+-------+ |
| 1082 | | :const:`PCALL_POP` | 10 | |
| 1083 | +-------------------------------+-------+ |
Georg Brandl | 48310cd | 2009-01-03 21:18:54 +0000 | [diff] [blame] | 1084 | |
Christian Heimes | d8654cf | 2007-12-02 15:22:16 +0000 | [diff] [blame] | 1085 | :const:`PCALL_FAST_FUNCTION` means no argument tuple needs to be created. |
| 1086 | :const:`PCALL_FASTER_FUNCTION` means that the fast-path frame setup code is used. |
| 1087 | |
| 1088 | If there is a method call where the call can be optimized by changing |
| 1089 | the argument tuple and calling the function directly, it gets recorded |
| 1090 | twice. |
| 1091 | |
| 1092 | This function is only present if Python is compiled with :const:`CALL_PROFILE` |
| 1093 | defined. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 1094 | |
| 1095 | .. _advanced-debugging: |
| 1096 | |
| 1097 | Advanced Debugger Support |
| 1098 | ========================= |
| 1099 | |
| 1100 | .. sectionauthor:: Fred L. Drake, Jr. <fdrake@acm.org> |
| 1101 | |
| 1102 | |
| 1103 | These functions are only intended to be used by advanced debugging tools. |
| 1104 | |
| 1105 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 1106 | .. c:function:: PyInterpreterState* PyInterpreterState_Head() |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 1107 | |
| 1108 | Return the interpreter state object at the head of the list of all such objects. |
| 1109 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 1110 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 1111 | .. c:function:: PyInterpreterState* PyInterpreterState_Next(PyInterpreterState *interp) |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 1112 | |
| 1113 | Return the next interpreter state object after *interp* from the list of all |
| 1114 | such objects. |
| 1115 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 1116 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 1117 | .. c:function:: PyThreadState * PyInterpreterState_ThreadHead(PyInterpreterState *interp) |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 1118 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 1119 | Return the a pointer to the first :c:type:`PyThreadState` object in the list of |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 1120 | threads associated with the interpreter *interp*. |
| 1121 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 1122 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 1123 | .. c:function:: PyThreadState* PyThreadState_Next(PyThreadState *tstate) |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 1124 | |
| 1125 | Return the next thread state object after *tstate* from the list of all such |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 1126 | objects belonging to the same :c:type:`PyInterpreterState` object. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 1127 | |