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() |
| 20 | single: PyEval_ReleaseLock() |
| 21 | single: PyEval_AcquireLock() |
| 22 | single: modules (in module sys) |
| 23 | single: path (in module sys) |
Georg Brandl | 1a3284e | 2007-12-02 09:40:06 +0000 | [diff] [blame] | 24 | module: builtins |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 25 | module: __main__ |
| 26 | module: sys |
| 27 | triple: module; search; path |
| 28 | single: PySys_SetArgv() |
Antoine Pitrou | f978fac | 2010-05-21 17:25:34 +0000 | [diff] [blame] | 29 | single: PySys_SetArgvEx() |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 30 | single: Py_Finalize() |
| 31 | |
| 32 | Initialize the Python interpreter. In an application embedding Python, this |
| 33 | 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] | 34 | exception of :c:func:`Py_SetProgramName`, :c:func:`Py_SetPath`, |
| 35 | :c:func:`PyEval_InitThreads`, :c:func:`PyEval_ReleaseLock`, and |
| 36 | :c:func:`PyEval_AcquireLock`. This initializes |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 37 | the table of loaded modules (``sys.modules``), and creates the fundamental |
Georg Brandl | 1a3284e | 2007-12-02 09:40:06 +0000 | [diff] [blame] | 38 | modules :mod:`builtins`, :mod:`__main__` and :mod:`sys`. It also initializes |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 39 | 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] | 40 | :c:func:`PySys_SetArgvEx` for that. This is a no-op when called for a second time |
| 41 | (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] | 42 | fatal error if the initialization fails. |
| 43 | |
| 44 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 45 | .. c:function:: void Py_InitializeEx(int initsigs) |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 46 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 47 | 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] | 48 | *initsigs* is 0, it skips initialization registration of signal handlers, which |
| 49 | might be useful when Python is embedded. |
| 50 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 51 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 52 | .. c:function:: int Py_IsInitialized() |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 53 | |
| 54 | Return true (nonzero) when the Python interpreter has been initialized, false |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 55 | (zero) if not. After :c:func:`Py_Finalize` is called, this returns false until |
| 56 | :c:func:`Py_Initialize` is called again. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 57 | |
| 58 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 59 | .. c:function:: void Py_Finalize() |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 60 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 61 | 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] | 62 | Python/C API functions, and destroy all sub-interpreters (see |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 63 | :c:func:`Py_NewInterpreter` below) that were created and not yet destroyed since |
| 64 | 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] | 65 | 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] | 66 | 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] | 67 | value; errors during finalization are ignored. |
| 68 | |
| 69 | This function is provided for a number of reasons. An embedding application |
| 70 | might want to restart Python without having to restart the application itself. |
| 71 | An application that has loaded the Python interpreter from a dynamically |
| 72 | loadable library (or DLL) might want to free all memory allocated by Python |
| 73 | before unloading the DLL. During a hunt for memory leaks in an application a |
| 74 | developer might want to free all memory allocated by Python before exiting from |
| 75 | the application. |
| 76 | |
| 77 | **Bugs and caveats:** The destruction of modules and objects in modules is done |
| 78 | in random order; this may cause destructors (:meth:`__del__` methods) to fail |
| 79 | when they depend on other objects (even functions) or modules. Dynamically |
| 80 | loaded extension modules loaded by Python are not unloaded. Small amounts of |
| 81 | memory allocated by the Python interpreter may not be freed (if you find a leak, |
| 82 | please report it). Memory tied up in circular references between objects is not |
| 83 | freed. Some memory allocated by extension modules may not be freed. Some |
| 84 | extensions may not work properly if their initialization routine is called more |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 85 | than once; this can happen if an application calls :c:func:`Py_Initialize` and |
| 86 | :c:func:`Py_Finalize` more than once. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 87 | |
| 88 | |
Antoine Pitrou | 8b50b83 | 2011-01-15 11:57:42 +0000 | [diff] [blame] | 89 | Process-wide parameters |
| 90 | ======================= |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 91 | |
| 92 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 93 | .. c:function:: void Py_SetProgramName(wchar_t *name) |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 94 | |
| 95 | .. index:: |
| 96 | single: Py_Initialize() |
| 97 | single: main() |
| 98 | single: Py_GetPath() |
| 99 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 100 | 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] | 101 | 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] | 102 | 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] | 103 | (converted to wide characters). |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 104 | 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] | 105 | the Python run-time libraries relative to the interpreter executable. The |
| 106 | default value is ``'python'``. The argument should point to a |
Martin v. Löwis | 790465f | 2008-04-05 20:41:37 +0000 | [diff] [blame] | 107 | zero-terminated wide character string in static storage whose contents will not |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 108 | change for the duration of the program's execution. No code in the Python |
| 109 | interpreter will change the contents of this storage. |
| 110 | |
| 111 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 112 | .. c:function:: wchar* Py_GetProgramName() |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 113 | |
| 114 | .. index:: single: Py_SetProgramName() |
| 115 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 116 | 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] | 117 | The returned string points into static storage; the caller should not modify its |
| 118 | value. |
| 119 | |
| 120 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 121 | .. c:function:: wchar_t* Py_GetPrefix() |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 122 | |
| 123 | Return the *prefix* for installed platform-independent files. This is derived |
| 124 | through a number of complicated rules from the program name set with |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 125 | :c:func:`Py_SetProgramName` and some environment variables; for example, if the |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 126 | program name is ``'/usr/local/bin/python'``, the prefix is ``'/usr/local'``. The |
| 127 | returned string points into static storage; the caller should not modify its |
| 128 | value. This corresponds to the :makevar:`prefix` variable in the top-level |
| 129 | :file:`Makefile` and the :option:`--prefix` argument to the :program:`configure` |
| 130 | script at build time. The value is available to Python code as ``sys.prefix``. |
| 131 | It is only useful on Unix. See also the next function. |
| 132 | |
| 133 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 134 | .. c:function:: wchar_t* Py_GetExecPrefix() |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 135 | |
| 136 | Return the *exec-prefix* for installed platform-*dependent* files. This is |
| 137 | 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] | 138 | :c:func:`Py_SetProgramName` and some environment variables; for example, if the |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 139 | program name is ``'/usr/local/bin/python'``, the exec-prefix is |
| 140 | ``'/usr/local'``. The returned string points into static storage; the caller |
| 141 | should not modify its value. This corresponds to the :makevar:`exec_prefix` |
| 142 | variable in the top-level :file:`Makefile` and the :option:`--exec-prefix` |
| 143 | argument to the :program:`configure` script at build time. The value is |
| 144 | available to Python code as ``sys.exec_prefix``. It is only useful on Unix. |
| 145 | |
| 146 | Background: The exec-prefix differs from the prefix when platform dependent |
| 147 | files (such as executables and shared libraries) are installed in a different |
| 148 | directory tree. In a typical installation, platform dependent files may be |
| 149 | installed in the :file:`/usr/local/plat` subtree while platform independent may |
| 150 | be installed in :file:`/usr/local`. |
| 151 | |
| 152 | Generally speaking, a platform is a combination of hardware and software |
| 153 | families, e.g. Sparc machines running the Solaris 2.x operating system are |
| 154 | considered the same platform, but Intel machines running Solaris 2.x are another |
| 155 | platform, and Intel machines running Linux are yet another platform. Different |
| 156 | major revisions of the same operating system generally also form different |
| 157 | platforms. Non-Unix operating systems are a different story; the installation |
| 158 | strategies on those systems are so different that the prefix and exec-prefix are |
| 159 | meaningless, and set to the empty string. Note that compiled Python bytecode |
| 160 | files are platform independent (but not independent from the Python version by |
| 161 | which they were compiled!). |
| 162 | |
| 163 | System administrators will know how to configure the :program:`mount` or |
| 164 | :program:`automount` programs to share :file:`/usr/local` between platforms |
| 165 | while having :file:`/usr/local/plat` be a different filesystem for each |
| 166 | platform. |
| 167 | |
| 168 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 169 | .. c:function:: wchar_t* Py_GetProgramFullPath() |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 170 | |
| 171 | .. index:: |
| 172 | single: Py_SetProgramName() |
| 173 | single: executable (in module sys) |
| 174 | |
| 175 | Return the full program name of the Python executable; this is computed as a |
| 176 | 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] | 177 | (set by :c:func:`Py_SetProgramName` above). The returned string points into |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 178 | static storage; the caller should not modify its value. The value is available |
| 179 | to Python code as ``sys.executable``. |
| 180 | |
| 181 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 182 | .. c:function:: wchar_t* Py_GetPath() |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 183 | |
| 184 | .. index:: |
| 185 | triple: module; search; path |
| 186 | single: path (in module sys) |
Kristján Valur Jónsson | 3b69db2 | 2010-09-27 05:32:54 +0000 | [diff] [blame] | 187 | single: Py_SetPath() |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 188 | |
Benjamin Peterson | 46a9900 | 2010-01-09 18:45:30 +0000 | [diff] [blame] | 189 | 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] | 190 | (set by :c:func:`Py_SetProgramName` above) and some environment variables. |
Benjamin Peterson | 46a9900 | 2010-01-09 18:45:30 +0000 | [diff] [blame] | 191 | The returned string consists of a series of directory names separated by a |
| 192 | platform dependent delimiter character. The delimiter character is ``':'`` |
| 193 | on Unix and Mac OS X, ``';'`` on Windows. The returned string points into |
| 194 | static storage; the caller should not modify its value. The list |
| 195 | :data:`sys.path` is initialized with this value on interpreter startup; it |
| 196 | can be (and usually is) modified later to change the search path for loading |
| 197 | modules. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 198 | |
Christian Heimes | 5b5e81c | 2007-12-31 16:14:33 +0000 | [diff] [blame] | 199 | .. XXX should give the exact rules |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 200 | |
| 201 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 202 | .. c:function:: void Py_SetPath(const wchar_t *) |
Kristján Valur Jónsson | 3b69db2 | 2010-09-27 05:32:54 +0000 | [diff] [blame] | 203 | |
| 204 | .. index:: |
| 205 | triple: module; search; path |
| 206 | single: path (in module sys) |
| 207 | single: Py_GetPath() |
| 208 | |
| 209 | Set the default module search path. If this function is called before |
Georg Brandl | fa4f7f9 | 2010-10-06 10:14:08 +0000 | [diff] [blame] | 210 | :c:func:`Py_Initialize`, then :c:func:`Py_GetPath` won't attempt to compute a |
| 211 | default search path but uses the one provided instead. This is useful if |
| 212 | Python is embedded by an application that has full knowledge of the location |
| 213 | of all modules. The path components should be separated by semicolons. |
Kristján Valur Jónsson | 3b69db2 | 2010-09-27 05:32:54 +0000 | [diff] [blame] | 214 | |
Georg Brandl | fa4f7f9 | 2010-10-06 10:14:08 +0000 | [diff] [blame] | 215 | This also causes :data:`sys.executable` to be set only to the raw program |
| 216 | name (see :c:func:`Py_SetProgramName`) and for :data:`sys.prefix` and |
| 217 | :data:`sys.exec_prefix` to be empty. It is up to the caller to modify these |
| 218 | if required after calling :c:func:`Py_Initialize`. |
| 219 | |
Kristján Valur Jónsson | 3b69db2 | 2010-09-27 05:32:54 +0000 | [diff] [blame] | 220 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 221 | .. c:function:: const char* Py_GetVersion() |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 222 | |
| 223 | Return the version of this Python interpreter. This is a string that looks |
| 224 | something like :: |
| 225 | |
Georg Brandl | e6bcc91 | 2008-05-12 18:05:20 +0000 | [diff] [blame] | 226 | "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] | 227 | |
| 228 | .. index:: single: version (in module sys) |
| 229 | |
| 230 | The first word (up to the first space character) is the current Python version; |
| 231 | the first three characters are the major and minor version separated by a |
| 232 | period. The returned string points into static storage; the caller should not |
Georg Brandl | e6bcc91 | 2008-05-12 18:05:20 +0000 | [diff] [blame] | 233 | 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] | 234 | |
| 235 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 236 | .. c:function:: const char* Py_GetPlatform() |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 237 | |
| 238 | .. index:: single: platform (in module sys) |
| 239 | |
| 240 | Return the platform identifier for the current platform. On Unix, this is |
| 241 | formed from the "official" name of the operating system, converted to lower |
| 242 | case, followed by the major revision number; e.g., for Solaris 2.x, which is |
| 243 | also known as SunOS 5.x, the value is ``'sunos5'``. On Mac OS X, it is |
| 244 | ``'darwin'``. On Windows, it is ``'win'``. The returned string points into |
| 245 | static storage; the caller should not modify its value. The value is available |
| 246 | to Python code as ``sys.platform``. |
| 247 | |
| 248 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 249 | .. c:function:: const char* Py_GetCopyright() |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 250 | |
| 251 | Return the official copyright string for the current Python version, for example |
| 252 | |
| 253 | ``'Copyright 1991-1995 Stichting Mathematisch Centrum, Amsterdam'`` |
| 254 | |
| 255 | .. index:: single: copyright (in module sys) |
| 256 | |
| 257 | The returned string points into static storage; the caller should not modify its |
| 258 | value. The value is available to Python code as ``sys.copyright``. |
| 259 | |
| 260 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 261 | .. c:function:: const char* Py_GetCompiler() |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 262 | |
| 263 | Return an indication of the compiler used to build the current Python version, |
| 264 | in square brackets, for example:: |
| 265 | |
| 266 | "[GCC 2.7.2.2]" |
| 267 | |
| 268 | .. index:: single: version (in module sys) |
| 269 | |
| 270 | The returned string points into static storage; the caller should not modify its |
| 271 | value. The value is available to Python code as part of the variable |
| 272 | ``sys.version``. |
| 273 | |
| 274 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 275 | .. c:function:: const char* Py_GetBuildInfo() |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 276 | |
| 277 | Return information about the sequence number and build date and time of the |
| 278 | current Python interpreter instance, for example :: |
| 279 | |
| 280 | "#67, Aug 1 1997, 22:34:28" |
| 281 | |
| 282 | .. index:: single: version (in module sys) |
| 283 | |
| 284 | The returned string points into static storage; the caller should not modify its |
| 285 | value. The value is available to Python code as part of the variable |
| 286 | ``sys.version``. |
| 287 | |
| 288 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 289 | .. c:function:: void PySys_SetArgvEx(int argc, wchar_t **argv, int updatepath) |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 290 | |
| 291 | .. index:: |
| 292 | single: main() |
| 293 | single: Py_FatalError() |
| 294 | single: argv (in module sys) |
| 295 | |
Benjamin Peterson | 5c6d787 | 2009-02-06 02:40:07 +0000 | [diff] [blame] | 296 | Set :data:`sys.argv` based on *argc* and *argv*. These parameters are |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 297 | 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] | 298 | difference that the first entry should refer to the script file to be |
| 299 | executed rather than the executable hosting the Python interpreter. If there |
| 300 | isn't a script that will be run, the first entry in *argv* can be an empty |
| 301 | string. If this function fails to initialize :data:`sys.argv`, a fatal |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 302 | condition is signalled using :c:func:`Py_FatalError`. |
Benjamin Peterson | 5c6d787 | 2009-02-06 02:40:07 +0000 | [diff] [blame] | 303 | |
Antoine Pitrou | f978fac | 2010-05-21 17:25:34 +0000 | [diff] [blame] | 304 | If *updatepath* is zero, this is all the function does. If *updatepath* |
| 305 | is non-zero, the function also modifies :data:`sys.path` according to the |
| 306 | following algorithm: |
| 307 | |
| 308 | - If the name of an existing script is passed in ``argv[0]``, the absolute |
| 309 | path of the directory where the script is located is prepended to |
| 310 | :data:`sys.path`. |
| 311 | - Otherwise (that is, if *argc* is 0 or ``argv[0]`` doesn't point |
| 312 | to an existing file name), an empty string is prepended to |
| 313 | :data:`sys.path`, which is the same as prepending the current working |
| 314 | directory (``"."``). |
| 315 | |
| 316 | .. note:: |
| 317 | It is recommended that applications embedding the Python interpreter |
| 318 | for purposes other than executing a single script pass 0 as *updatepath*, |
| 319 | and update :data:`sys.path` themselves if desired. |
| 320 | See `CVE-2008-5983 <http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2008-5983>`_. |
| 321 | |
| 322 | On versions before 3.1.3, you can achieve the same effect by manually |
| 323 | popping the first :data:`sys.path` element after having called |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 324 | :c:func:`PySys_SetArgv`, for example using:: |
Antoine Pitrou | f978fac | 2010-05-21 17:25:34 +0000 | [diff] [blame] | 325 | |
| 326 | PyRun_SimpleString("import sys; sys.path.pop(0)\n"); |
| 327 | |
| 328 | .. versionadded:: 3.1.3 |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 329 | |
Christian Heimes | 5b5e81c | 2007-12-31 16:14:33 +0000 | [diff] [blame] | 330 | .. XXX impl. doesn't seem consistent in allowing 0/NULL for the params; |
| 331 | check w/ Guido. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 332 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 333 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 334 | .. c:function:: void PySys_SetArgv(int argc, wchar_t **argv) |
Antoine Pitrou | f978fac | 2010-05-21 17:25:34 +0000 | [diff] [blame] | 335 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 336 | 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] | 337 | |
| 338 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 339 | .. c:function:: void Py_SetPythonHome(wchar_t *home) |
Benjamin Peterson | 5c6d787 | 2009-02-06 02:40:07 +0000 | [diff] [blame] | 340 | |
| 341 | Set the default "home" directory, that is, the location of the standard |
Georg Brandl | de0ab5e | 2010-12-02 18:02:01 +0000 | [diff] [blame] | 342 | Python libraries. See :envvar:`PYTHONHOME` for the meaning of the |
| 343 | argument string. |
| 344 | |
Benjamin Peterson | 4ac9ce4 | 2009-10-04 14:49:41 +0000 | [diff] [blame] | 345 | The argument should point to a zero-terminated character string in static |
| 346 | storage whose contents will not change for the duration of the program's |
| 347 | execution. No code in the Python interpreter will change the contents of |
| 348 | this storage. |
Benjamin Peterson | 5c6d787 | 2009-02-06 02:40:07 +0000 | [diff] [blame] | 349 | |
| 350 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 351 | .. c:function:: w_char* Py_GetPythonHome() |
Benjamin Peterson | 5c6d787 | 2009-02-06 02:40:07 +0000 | [diff] [blame] | 352 | |
| 353 | 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] | 354 | :c:func:`Py_SetPythonHome`, or the value of the :envvar:`PYTHONHOME` |
Benjamin Peterson | 5c6d787 | 2009-02-06 02:40:07 +0000 | [diff] [blame] | 355 | environment variable if it is set. |
| 356 | |
| 357 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 358 | .. _threads: |
| 359 | |
| 360 | Thread State and the Global Interpreter Lock |
| 361 | ============================================ |
| 362 | |
| 363 | .. index:: |
| 364 | single: global interpreter lock |
| 365 | single: interpreter lock |
| 366 | single: lock, interpreter |
| 367 | |
Georg Brandl | f285bcc | 2010-10-19 21:07:16 +0000 | [diff] [blame] | 368 | The Python interpreter is not fully thread-safe. In order to support |
Benjamin Peterson | ef3e4c2 | 2009-04-11 19:48:14 +0000 | [diff] [blame] | 369 | multi-threaded Python programs, there's a global lock, called the :dfn:`global |
| 370 | interpreter lock` or :dfn:`GIL`, that must be held by the current thread before |
| 371 | it can safely access Python objects. Without the lock, even the simplest |
| 372 | operations could cause problems in a multi-threaded program: for example, when |
| 373 | two threads simultaneously increment the reference count of the same object, the |
| 374 | reference count could end up being incremented only once instead of twice. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 375 | |
| 376 | .. index:: single: setcheckinterval() (in module sys) |
| 377 | |
| 378 | Therefore, the rule exists that only the thread that has acquired the global |
| 379 | interpreter lock may operate on Python objects or call Python/C API functions. |
| 380 | In order to support multi-threaded Python programs, the interpreter regularly |
| 381 | releases and reacquires the lock --- by default, every 100 bytecode instructions |
| 382 | (this can be changed with :func:`sys.setcheckinterval`). The lock is also |
| 383 | released and reacquired around potentially blocking I/O operations like reading |
| 384 | or writing a file, so that other threads can run while the thread that requests |
| 385 | the I/O is waiting for the I/O operation to complete. |
| 386 | |
| 387 | .. index:: |
| 388 | single: PyThreadState |
| 389 | single: PyThreadState |
| 390 | |
| 391 | The Python interpreter needs to keep some bookkeeping information separate per |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 392 | thread --- for this it uses a data structure called :c:type:`PyThreadState`. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 393 | There's one global variable, however: the pointer to the current |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 394 | :c:type:`PyThreadState` structure. Before the addition of :dfn:`thread-local |
Benjamin Peterson | 25c95f1 | 2009-05-08 20:42:26 +0000 | [diff] [blame] | 395 | storage` (:dfn:`TLS`) the current thread state had to be manipulated |
| 396 | explicitly. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 397 | |
| 398 | This is easy enough in most cases. Most code manipulating the global |
| 399 | interpreter lock has the following simple structure:: |
| 400 | |
| 401 | Save the thread state in a local variable. |
Benjamin Peterson | ef3e4c2 | 2009-04-11 19:48:14 +0000 | [diff] [blame] | 402 | Release the global interpreter lock. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 403 | ...Do some blocking I/O operation... |
Benjamin Peterson | ef3e4c2 | 2009-04-11 19:48:14 +0000 | [diff] [blame] | 404 | Reacquire the global interpreter lock. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 405 | Restore the thread state from the local variable. |
| 406 | |
| 407 | This is so common that a pair of macros exists to simplify it:: |
| 408 | |
| 409 | Py_BEGIN_ALLOW_THREADS |
| 410 | ...Do some blocking I/O operation... |
| 411 | Py_END_ALLOW_THREADS |
| 412 | |
| 413 | .. index:: |
| 414 | single: Py_BEGIN_ALLOW_THREADS |
| 415 | single: Py_END_ALLOW_THREADS |
| 416 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 417 | The :c:macro:`Py_BEGIN_ALLOW_THREADS` macro opens a new block and declares a |
| 418 | hidden local variable; the :c:macro:`Py_END_ALLOW_THREADS` macro closes the |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 419 | block. Another advantage of using these two macros is that when Python is |
| 420 | compiled without thread support, they are defined empty, thus saving the thread |
Benjamin Peterson | ef3e4c2 | 2009-04-11 19:48:14 +0000 | [diff] [blame] | 421 | state and GIL manipulations. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 422 | |
| 423 | When thread support is enabled, the block above expands to the following code:: |
| 424 | |
| 425 | PyThreadState *_save; |
| 426 | |
| 427 | _save = PyEval_SaveThread(); |
| 428 | ...Do some blocking I/O operation... |
| 429 | PyEval_RestoreThread(_save); |
| 430 | |
| 431 | Using even lower level primitives, we can get roughly the same effect as |
| 432 | follows:: |
| 433 | |
| 434 | PyThreadState *_save; |
| 435 | |
| 436 | _save = PyThreadState_Swap(NULL); |
| 437 | PyEval_ReleaseLock(); |
| 438 | ...Do some blocking I/O operation... |
| 439 | PyEval_AcquireLock(); |
| 440 | PyThreadState_Swap(_save); |
| 441 | |
| 442 | .. index:: |
| 443 | single: PyEval_RestoreThread() |
| 444 | single: errno |
| 445 | single: PyEval_SaveThread() |
| 446 | single: PyEval_ReleaseLock() |
| 447 | single: PyEval_AcquireLock() |
| 448 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 449 | There are some subtle differences; in particular, :c:func:`PyEval_RestoreThread` |
| 450 | saves and restores the value of the global variable :c:data:`errno`, since the |
| 451 | lock manipulation does not guarantee that :c:data:`errno` is left alone. Also, |
| 452 | when thread support is disabled, :c:func:`PyEval_SaveThread` and |
| 453 | :c:func:`PyEval_RestoreThread` don't manipulate the GIL; in this case, |
| 454 | :c:func:`PyEval_ReleaseLock` and :c:func:`PyEval_AcquireLock` are not available. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 455 | This is done so that dynamically loaded extensions compiled with thread support |
| 456 | enabled can be loaded by an interpreter that was compiled with disabled thread |
| 457 | support. |
| 458 | |
| 459 | The global interpreter lock is used to protect the pointer to the current thread |
| 460 | state. When releasing the lock and saving the thread state, the current thread |
| 461 | state pointer must be retrieved before the lock is released (since another |
| 462 | thread could immediately acquire the lock and store its own thread state in the |
| 463 | global variable). Conversely, when acquiring the lock and restoring the thread |
| 464 | state, the lock must be acquired before storing the thread state pointer. |
| 465 | |
Jeroen Ruigrok van der Werven | 939c178 | 2009-04-26 20:25:45 +0000 | [diff] [blame] | 466 | It is important to note that when threads are created from C, they don't have |
| 467 | the global interpreter lock, nor is there a thread state data structure for |
| 468 | them. Such threads must bootstrap themselves into existence, by first |
| 469 | creating a thread state data structure, then acquiring the lock, and finally |
| 470 | storing their thread state pointer, before they can start using the Python/C |
| 471 | API. When they are done, they should reset the thread state pointer, release |
| 472 | the lock, and finally free their thread state data structure. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 473 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 474 | Threads can take advantage of the :c:func:`PyGILState_\*` functions to do all of |
Georg Brandl | e6bcc91 | 2008-05-12 18:05:20 +0000 | [diff] [blame] | 475 | the above automatically. The typical idiom for calling into Python from a C |
| 476 | thread is now:: |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 477 | |
| 478 | PyGILState_STATE gstate; |
| 479 | gstate = PyGILState_Ensure(); |
| 480 | |
| 481 | /* Perform Python actions here. */ |
| 482 | result = CallSomeFunction(); |
| 483 | /* evaluate result */ |
| 484 | |
| 485 | /* Release the thread. No Python API allowed beyond this point. */ |
| 486 | PyGILState_Release(gstate); |
| 487 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 488 | Note that the :c:func:`PyGILState_\*` functions assume there is only one global |
| 489 | interpreter (created automatically by :c:func:`Py_Initialize`). Python still |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 490 | supports the creation of additional interpreters (using |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 491 | :c:func:`Py_NewInterpreter`), but mixing multiple interpreters and the |
| 492 | :c:func:`PyGILState_\*` API is unsupported. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 493 | |
Benjamin Peterson | 0df35a9 | 2009-10-04 20:32:25 +0000 | [diff] [blame] | 494 | 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] | 495 | 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] | 496 | process forks only the thread that issued the fork will exist. That also |
| 497 | means any locks held by other threads will never be released. Python solves |
| 498 | this for :func:`os.fork` by acquiring the locks it uses internally before |
| 499 | the fork, and releasing them afterwards. In addition, it resets any |
| 500 | :ref:`lock-objects` in the child. When extending or embedding Python, there |
| 501 | is no way to inform Python of additional (non-Python) locks that need to be |
| 502 | acquired before or reset after a fork. OS facilities such as |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 503 | :c:func:`posix_atfork` would need to be used to accomplish the same thing. |
| 504 | Additionally, when extending or embedding Python, calling :c:func:`fork` |
Benjamin Peterson | 0df35a9 | 2009-10-04 20:32:25 +0000 | [diff] [blame] | 505 | directly rather than through :func:`os.fork` (and returning to or calling |
| 506 | into Python) may result in a deadlock by one of Python's internal locks |
| 507 | being held by a thread that is defunct after the fork. |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 508 | :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] | 509 | always able to. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 510 | |
Antoine Pitrou | 8b50b83 | 2011-01-15 11:57:42 +0000 | [diff] [blame] | 511 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 512 | .. c:type:: PyInterpreterState |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 513 | |
| 514 | This data structure represents the state shared by a number of cooperating |
| 515 | threads. Threads belonging to the same interpreter share their module |
| 516 | administration and a few other internal items. There are no public members in |
| 517 | this structure. |
| 518 | |
| 519 | Threads belonging to different interpreters initially share nothing, except |
| 520 | process state like available memory, open file descriptors and such. The global |
| 521 | interpreter lock is also shared by all threads, regardless of to which |
| 522 | interpreter they belong. |
| 523 | |
| 524 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 525 | .. c:type:: PyThreadState |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 526 | |
| 527 | 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] | 528 | data member is :c:type:`PyInterpreterState \*`:attr:`interp`, which points to |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 529 | this thread's interpreter state. |
| 530 | |
| 531 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 532 | .. c:function:: void PyEval_InitThreads() |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 533 | |
| 534 | .. index:: |
| 535 | single: PyEval_ReleaseLock() |
| 536 | single: PyEval_ReleaseThread() |
| 537 | single: PyEval_SaveThread() |
| 538 | single: PyEval_RestoreThread() |
| 539 | |
| 540 | Initialize and acquire the global interpreter lock. It should be called in the |
| 541 | main thread before creating a second thread or engaging in any other thread |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 542 | operations such as :c:func:`PyEval_ReleaseLock` or |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 543 | ``PyEval_ReleaseThread(tstate)``. It is not needed before calling |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 544 | :c:func:`PyEval_SaveThread` or :c:func:`PyEval_RestoreThread`. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 545 | |
| 546 | .. index:: single: Py_Initialize() |
| 547 | |
| 548 | 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] | 549 | before calling :c:func:`Py_Initialize`. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 550 | |
Georg Brandl | 2067bfd | 2008-05-25 13:05:15 +0000 | [diff] [blame] | 551 | .. index:: module: _thread |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 552 | |
Benjamin Peterson | ef3e4c2 | 2009-04-11 19:48:14 +0000 | [diff] [blame] | 553 | When only the main thread exists, no GIL operations are needed. This is a |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 554 | common situation (most Python programs do not use threads), and the lock |
Benjamin Peterson | ef3e4c2 | 2009-04-11 19:48:14 +0000 | [diff] [blame] | 555 | operations slow the interpreter down a bit. Therefore, the lock is not |
| 556 | created initially. This situation is equivalent to having acquired the lock: |
| 557 | when there is only a single thread, all object accesses are safe. Therefore, |
| 558 | when this function initializes the global interpreter lock, it also acquires |
| 559 | it. Before the Python :mod:`_thread` module creates a new thread, knowing |
| 560 | that either it has the lock or the lock hasn't been created yet, it calls |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 561 | :c:func:`PyEval_InitThreads`. When this call returns, it is guaranteed that |
Benjamin Peterson | ef3e4c2 | 2009-04-11 19:48:14 +0000 | [diff] [blame] | 562 | 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] | 563 | |
| 564 | It is **not** safe to call this function when it is unknown which thread (if |
| 565 | any) currently has the global interpreter lock. |
| 566 | |
| 567 | This function is not available when thread support is disabled at compile time. |
| 568 | |
| 569 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 570 | .. c:function:: int PyEval_ThreadsInitialized() |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 571 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 572 | 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] | 573 | 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] | 574 | avoid calls to the locking API when running single-threaded. This function is |
| 575 | not available when thread support is disabled at compile time. |
| 576 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 577 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 578 | .. c:function:: void PyEval_AcquireLock() |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 579 | |
| 580 | Acquire the global interpreter lock. The lock must have been created earlier. |
| 581 | If this thread already has the lock, a deadlock ensues. This function is not |
| 582 | available when thread support is disabled at compile time. |
| 583 | |
| 584 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 585 | .. c:function:: void PyEval_ReleaseLock() |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 586 | |
| 587 | Release the global interpreter lock. The lock must have been created earlier. |
| 588 | This function is not available when thread support is disabled at compile time. |
| 589 | |
| 590 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 591 | .. c:function:: void PyEval_AcquireThread(PyThreadState *tstate) |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 592 | |
| 593 | Acquire the global interpreter lock and set the current thread state to |
| 594 | *tstate*, which should not be *NULL*. The lock must have been created earlier. |
| 595 | If this thread already has the lock, deadlock ensues. This function is not |
| 596 | available when thread support is disabled at compile time. |
| 597 | |
| 598 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 599 | .. c:function:: void PyEval_ReleaseThread(PyThreadState *tstate) |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 600 | |
| 601 | Reset the current thread state to *NULL* and release the global interpreter |
| 602 | lock. The lock must have been created earlier and must be held by the current |
| 603 | thread. The *tstate* argument, which must not be *NULL*, is only used to check |
| 604 | that it represents the current thread state --- if it isn't, a fatal error is |
| 605 | reported. This function is not available when thread support is disabled at |
| 606 | compile time. |
| 607 | |
| 608 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 609 | .. c:function:: PyThreadState* PyEval_SaveThread() |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 610 | |
Benjamin Peterson | ef3e4c2 | 2009-04-11 19:48:14 +0000 | [diff] [blame] | 611 | Release the global interpreter lock (if it has been created and thread |
| 612 | support is enabled) and reset the thread state to *NULL*, returning the |
| 613 | previous thread state (which is not *NULL*). If the lock has been created, |
| 614 | the current thread must have acquired it. (This function is available even |
| 615 | when thread support is disabled at compile time.) |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 616 | |
| 617 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 618 | .. c:function:: void PyEval_RestoreThread(PyThreadState *tstate) |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 619 | |
Benjamin Peterson | ef3e4c2 | 2009-04-11 19:48:14 +0000 | [diff] [blame] | 620 | Acquire the global interpreter lock (if it has been created and thread |
| 621 | support is enabled) and set the thread state to *tstate*, which must not be |
| 622 | *NULL*. If the lock has been created, the current thread must not have |
| 623 | acquired it, otherwise deadlock ensues. (This function is available even |
| 624 | when thread support is disabled at compile time.) |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 625 | |
Christian Heimes | d8654cf | 2007-12-02 15:22:16 +0000 | [diff] [blame] | 626 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 627 | .. c:function:: void PyEval_ReInitThreads() |
Christian Heimes | d8654cf | 2007-12-02 15:22:16 +0000 | [diff] [blame] | 628 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 629 | 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] | 630 | created child processes don't hold locks referring to threads which |
| 631 | are not running in the child process. |
| 632 | |
| 633 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 634 | The following macros are normally used without a trailing semicolon; look for |
| 635 | example usage in the Python source distribution. |
| 636 | |
| 637 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 638 | .. c:macro:: Py_BEGIN_ALLOW_THREADS |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 639 | |
| 640 | This macro expands to ``{ PyThreadState *_save; _save = PyEval_SaveThread();``. |
| 641 | 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] | 642 | :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] | 643 | macro. It is a no-op when thread support is disabled at compile time. |
| 644 | |
| 645 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 646 | .. c:macro:: Py_END_ALLOW_THREADS |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 647 | |
| 648 | This macro expands to ``PyEval_RestoreThread(_save); }``. Note that it contains |
| 649 | a closing brace; it must be matched with an earlier |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 650 | :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] | 651 | this macro. It is a no-op when thread support is disabled at compile time. |
| 652 | |
| 653 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 654 | .. c:macro:: Py_BLOCK_THREADS |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 655 | |
| 656 | This macro expands to ``PyEval_RestoreThread(_save);``: it is equivalent to |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 657 | :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] | 658 | thread support is disabled at compile time. |
| 659 | |
| 660 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 661 | .. c:macro:: Py_UNBLOCK_THREADS |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 662 | |
| 663 | This macro expands to ``_save = PyEval_SaveThread();``: it is equivalent to |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 664 | :c:macro:`Py_BEGIN_ALLOW_THREADS` without the opening brace and variable |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 665 | declaration. It is a no-op when thread support is disabled at compile time. |
| 666 | |
| 667 | 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] | 668 | at compile time, and must be called only when the global interpreter lock has |
| 669 | been created. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 670 | |
| 671 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 672 | .. c:function:: PyInterpreterState* PyInterpreterState_New() |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 673 | |
Benjamin Peterson | ef3e4c2 | 2009-04-11 19:48:14 +0000 | [diff] [blame] | 674 | Create a new interpreter state object. The global interpreter lock need not |
| 675 | be held, but may be held if it is necessary to serialize calls to this |
| 676 | function. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 677 | |
| 678 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 679 | .. c:function:: void PyInterpreterState_Clear(PyInterpreterState *interp) |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 680 | |
Benjamin Peterson | ef3e4c2 | 2009-04-11 19:48:14 +0000 | [diff] [blame] | 681 | Reset all information in an interpreter state object. The global interpreter |
| 682 | lock must be held. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 683 | |
| 684 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 685 | .. c:function:: void PyInterpreterState_Delete(PyInterpreterState *interp) |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 686 | |
Benjamin Peterson | ef3e4c2 | 2009-04-11 19:48:14 +0000 | [diff] [blame] | 687 | Destroy an interpreter state object. The global interpreter lock need not be |
| 688 | 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] | 689 | :c:func:`PyInterpreterState_Clear`. |
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:: PyThreadState* PyThreadState_New(PyInterpreterState *interp) |
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 thread state object belonging to the given interpreter object. |
| 695 | The global interpreter lock need not be held, but may be held if it is |
| 696 | necessary to serialize calls to this 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 PyThreadState_Clear(PyThreadState *tstate) |
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 a thread state object. The global interpreter lock |
| 702 | 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 PyThreadState_Delete(PyThreadState *tstate) |
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 a thread state object. The global interpreter lock need not be held. |
| 708 | The thread 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:`PyThreadState_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_Get() |
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 | Return the current thread state. The global interpreter lock must be held. |
| 715 | When the current thread state is *NULL*, this issues a fatal error (so that |
| 716 | the caller needn't check for *NULL*). |
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:: PyThreadState* PyThreadState_Swap(PyThreadState *tstate) |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 720 | |
| 721 | Swap the current thread state with the thread state given by the argument |
Benjamin Peterson | ef3e4c2 | 2009-04-11 19:48:14 +0000 | [diff] [blame] | 722 | *tstate*, which may be *NULL*. The global interpreter lock 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:: PyObject* PyThreadState_GetDict() |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 726 | |
| 727 | Return a dictionary in which extensions can store thread-specific state |
| 728 | information. Each extension should use a unique key to use to store state in |
| 729 | the dictionary. It is okay to call this function when no current thread state |
| 730 | is available. If this function returns *NULL*, no exception has been raised and |
| 731 | the caller should assume no current thread state is available. |
| 732 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 733 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 734 | .. c:function:: int PyThreadState_SetAsyncExc(long id, PyObject *exc) |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 735 | |
| 736 | Asynchronously raise an exception in a thread. The *id* argument is the thread |
| 737 | id of the target thread; *exc* is the exception object to be raised. This |
| 738 | function does not steal any references to *exc*. To prevent naive misuse, you |
| 739 | must write your own C extension to call this. Must be called with the GIL held. |
| 740 | Returns the number of thread states modified; this is normally one, but will be |
| 741 | zero if the thread id isn't found. If *exc* is :const:`NULL`, the pending |
| 742 | exception (if any) for the thread is cleared. This raises no exceptions. |
| 743 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 744 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 745 | .. c:function:: PyGILState_STATE PyGILState_Ensure() |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 746 | |
Benjamin Peterson | ef3e4c2 | 2009-04-11 19:48:14 +0000 | [diff] [blame] | 747 | Ensure that the current thread is ready to call the Python C API regardless |
| 748 | of the current state of Python, or of the global interpreter lock. This may |
| 749 | be called as many times as desired by a thread as long as each call is |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 750 | matched with a call to :c:func:`PyGILState_Release`. In general, other |
| 751 | thread-related APIs may be used between :c:func:`PyGILState_Ensure` and |
| 752 | :c:func:`PyGILState_Release` calls as long as the thread state is restored to |
Benjamin Peterson | ef3e4c2 | 2009-04-11 19:48:14 +0000 | [diff] [blame] | 753 | its previous state before the Release(). For example, normal usage of the |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 754 | :c:macro:`Py_BEGIN_ALLOW_THREADS` and :c:macro:`Py_END_ALLOW_THREADS` macros is |
Benjamin Peterson | ef3e4c2 | 2009-04-11 19:48:14 +0000 | [diff] [blame] | 755 | acceptable. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 756 | |
| 757 | The return value is an opaque "handle" to the thread state when |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 758 | :c:func:`PyGILState_Ensure` was called, and must be passed to |
| 759 | :c:func:`PyGILState_Release` to ensure Python is left in the same state. Even |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 760 | though recursive calls are allowed, these handles *cannot* be shared - each |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 761 | unique call to :c:func:`PyGILState_Ensure` must save the handle for its call |
| 762 | to :c:func:`PyGILState_Release`. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 763 | |
| 764 | When the function returns, the current thread will hold the GIL. Failure is a |
| 765 | fatal error. |
| 766 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 767 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 768 | .. c:function:: void PyGILState_Release(PyGILState_STATE) |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 769 | |
| 770 | Release any resources previously acquired. After this call, Python's state will |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 771 | be the same as it was prior to the corresponding :c:func:`PyGILState_Ensure` call |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 772 | (but generally this state will be unknown to the caller, hence the use of the |
| 773 | GILState API.) |
| 774 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 775 | Every call to :c:func:`PyGILState_Ensure` must be matched by a call to |
| 776 | :c:func:`PyGILState_Release` on the same thread. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 777 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 778 | |
Antoine Pitrou | 8b50b83 | 2011-01-15 11:57:42 +0000 | [diff] [blame] | 779 | Sub-interpreter support |
| 780 | ======================= |
| 781 | |
| 782 | While in most uses, you will only embed a single Python interpreter, there |
| 783 | are cases where you need to create several independent interpreters in the |
| 784 | same process and perhaps even in the same thread. Sub-interpreters allow |
Antoine Pitrou | 9bf8d1c | 2011-01-15 12:21:53 +0000 | [diff] [blame^] | 785 | you to do that. You can switch between sub-interpreters using the |
| 786 | :c:func:`PyThreadState_Swap` function. You can create and destroy them |
| 787 | using the following functions: |
Antoine Pitrou | 8b50b83 | 2011-01-15 11:57:42 +0000 | [diff] [blame] | 788 | |
| 789 | |
| 790 | .. c:function:: PyThreadState* Py_NewInterpreter() |
| 791 | |
| 792 | .. index:: |
| 793 | module: builtins |
| 794 | module: __main__ |
| 795 | module: sys |
| 796 | single: stdout (in module sys) |
| 797 | single: stderr (in module sys) |
| 798 | single: stdin (in module sys) |
| 799 | |
| 800 | Create a new sub-interpreter. This is an (almost) totally separate environment |
| 801 | for the execution of Python code. In particular, the new interpreter has |
| 802 | separate, independent versions of all imported modules, including the |
| 803 | fundamental modules :mod:`builtins`, :mod:`__main__` and :mod:`sys`. The |
| 804 | table of loaded modules (``sys.modules``) and the module search path |
| 805 | (``sys.path``) are also separate. The new environment has no ``sys.argv`` |
| 806 | variable. It has new standard I/O stream file objects ``sys.stdin``, |
| 807 | ``sys.stdout`` and ``sys.stderr`` (however these refer to the same underlying |
| 808 | file descriptors). |
| 809 | |
| 810 | The return value points to the first thread state created in the new |
| 811 | sub-interpreter. This thread state is made in the current thread state. |
| 812 | Note that no actual thread is created; see the discussion of thread states |
| 813 | below. If creation of the new interpreter is unsuccessful, *NULL* is |
| 814 | returned; no exception is set since the exception state is stored in the |
| 815 | current thread state and there may not be a current thread state. (Like all |
| 816 | other Python/C API functions, the global interpreter lock must be held before |
| 817 | calling this function and is still held when it returns; however, unlike most |
| 818 | other Python/C API functions, there needn't be a current thread state on |
| 819 | entry.) |
| 820 | |
| 821 | .. index:: |
| 822 | single: Py_Finalize() |
| 823 | single: Py_Initialize() |
| 824 | |
| 825 | Extension modules are shared between (sub-)interpreters as follows: the first |
| 826 | time a particular extension is imported, it is initialized normally, and a |
| 827 | (shallow) copy of its module's dictionary is squirreled away. When the same |
| 828 | extension is imported by another (sub-)interpreter, a new module is initialized |
| 829 | and filled with the contents of this copy; the extension's ``init`` function is |
| 830 | not called. Note that this is different from what happens when an extension is |
| 831 | imported after the interpreter has been completely re-initialized by calling |
| 832 | :c:func:`Py_Finalize` and :c:func:`Py_Initialize`; in that case, the extension's |
| 833 | ``initmodule`` function *is* called again. |
| 834 | |
| 835 | .. index:: single: close() (in module os) |
| 836 | |
| 837 | |
| 838 | .. c:function:: void Py_EndInterpreter(PyThreadState *tstate) |
| 839 | |
| 840 | .. index:: single: Py_Finalize() |
| 841 | |
| 842 | Destroy the (sub-)interpreter represented by the given thread state. The given |
| 843 | thread state must be the current thread state. See the discussion of thread |
| 844 | states below. When the call returns, the current thread state is *NULL*. All |
| 845 | thread states associated with this interpreter are destroyed. (The global |
| 846 | interpreter lock must be held before calling this function and is still held |
| 847 | when it returns.) :c:func:`Py_Finalize` will destroy all sub-interpreters that |
| 848 | haven't been explicitly destroyed at that point. |
| 849 | |
| 850 | |
| 851 | Bugs and caveats |
| 852 | ---------------- |
| 853 | |
| 854 | Because sub-interpreters (and the main interpreter) are part of the same |
| 855 | process, the insulation between them isn't perfect --- for example, using |
| 856 | low-level file operations like :func:`os.close` they can |
| 857 | (accidentally or maliciously) affect each other's open files. Because of the |
| 858 | way extensions are shared between (sub-)interpreters, some extensions may not |
| 859 | work properly; this is especially likely when the extension makes use of |
| 860 | (static) global variables, or when the extension manipulates its module's |
| 861 | dictionary after its initialization. It is possible to insert objects created |
| 862 | in one sub-interpreter into a namespace of another sub-interpreter; this should |
| 863 | be done with great care to avoid sharing user-defined functions, methods, |
| 864 | instances or classes between sub-interpreters, since import operations executed |
| 865 | 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] | 866 | modules. |
Antoine Pitrou | 8b50b83 | 2011-01-15 11:57:42 +0000 | [diff] [blame] | 867 | |
Antoine Pitrou | f1dfe73 | 2011-01-15 12:10:48 +0000 | [diff] [blame] | 868 | Also note that combining this functionality with :c:func:`PyGILState_\*` APIs |
| 869 | is delicate, become these APIs assume a bijection between Python thread states |
| 870 | and OS-level threads, an assumption broken by the presence of sub-interpreters. |
| 871 | It is highly recommended that you don't switch sub-interpreters between a pair |
| 872 | of matching :c:func:`PyGILState_Ensure` and :c:func:`PyGILState_Release` calls. |
| 873 | Furthermore, extensions (such as :mod:`ctypes`) using these APIs to allow calling |
| 874 | of Python code from non-Python created threads will probably be broken when using |
| 875 | sub-interpreters. |
Antoine Pitrou | 8b50b83 | 2011-01-15 11:57:42 +0000 | [diff] [blame] | 876 | |
Benjamin Peterson | a54c909 | 2009-01-13 02:11:23 +0000 | [diff] [blame] | 877 | |
| 878 | Asynchronous Notifications |
| 879 | ========================== |
| 880 | |
Benjamin Peterson | d23f822 | 2009-04-05 19:13:16 +0000 | [diff] [blame] | 881 | A mechanism is provided to make asynchronous notifications to the main |
Benjamin Peterson | a54c909 | 2009-01-13 02:11:23 +0000 | [diff] [blame] | 882 | interpreter thread. These notifications take the form of a function |
| 883 | pointer and a void argument. |
| 884 | |
| 885 | .. index:: single: setcheckinterval() (in module sys) |
| 886 | |
Benjamin Peterson | ef3e4c2 | 2009-04-11 19:48:14 +0000 | [diff] [blame] | 887 | Every check interval, when the global interpreter lock is released and |
Ezio Melotti | 0639d5a | 2009-12-19 23:26:38 +0000 | [diff] [blame] | 888 | 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] | 889 | for example by asynchronous IO handlers. The notification can be scheduled from |
| 890 | a worker thread and the actual call than made at the earliest convenience by the |
| 891 | main thread where it has possession of the global interpreter lock and can |
| 892 | perform any Python API calls. |
Benjamin Peterson | a54c909 | 2009-01-13 02:11:23 +0000 | [diff] [blame] | 893 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 894 | .. c:function:: void Py_AddPendingCall( int (*func)(void *, void *arg) ) |
Benjamin Peterson | a54c909 | 2009-01-13 02:11:23 +0000 | [diff] [blame] | 895 | |
| 896 | .. index:: single: Py_AddPendingCall() |
| 897 | |
Benjamin Peterson | ef3e4c2 | 2009-04-11 19:48:14 +0000 | [diff] [blame] | 898 | Post a notification to the Python main thread. If successful, *func* will be |
| 899 | called with the argument *arg* at the earliest convenience. *func* will be |
| 900 | called having the global interpreter lock held and can thus use the full |
| 901 | Python API and can take any action such as setting object attributes to |
| 902 | signal IO completion. It must return 0 on success, or -1 signalling an |
| 903 | exception. The notification function won't be interrupted to perform another |
| 904 | asynchronous notification recursively, but it can still be interrupted to |
| 905 | 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] | 906 | calls back into Python code. |
Benjamin Peterson | a54c909 | 2009-01-13 02:11:23 +0000 | [diff] [blame] | 907 | |
| 908 | 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] | 909 | scheduled. Otherwise, for example if the notification buffer is full, it |
| 910 | returns -1 without setting any exception. |
Benjamin Peterson | a54c909 | 2009-01-13 02:11:23 +0000 | [diff] [blame] | 911 | |
Benjamin Peterson | ef3e4c2 | 2009-04-11 19:48:14 +0000 | [diff] [blame] | 912 | This function can be called on any thread, be it a Python thread or some |
| 913 | other system thread. If it is a Python thread, it doesn't matter if it holds |
| 914 | the global interpreter lock or not. |
Benjamin Peterson | a54c909 | 2009-01-13 02:11:23 +0000 | [diff] [blame] | 915 | |
Georg Brandl | 705d9d5 | 2009-05-05 09:29:50 +0000 | [diff] [blame] | 916 | .. versionadded:: 3.1 |
Benjamin Peterson | a54c909 | 2009-01-13 02:11:23 +0000 | [diff] [blame] | 917 | |
| 918 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 919 | .. _profiling: |
| 920 | |
| 921 | Profiling and Tracing |
| 922 | ===================== |
| 923 | |
| 924 | .. sectionauthor:: Fred L. Drake, Jr. <fdrake@acm.org> |
| 925 | |
| 926 | |
| 927 | The Python interpreter provides some low-level support for attaching profiling |
| 928 | and execution tracing facilities. These are used for profiling, debugging, and |
| 929 | coverage analysis tools. |
| 930 | |
Georg Brandl | e6bcc91 | 2008-05-12 18:05:20 +0000 | [diff] [blame] | 931 | This C interface allows the profiling or tracing code to avoid the overhead of |
| 932 | calling through Python-level callable objects, making a direct C function call |
| 933 | instead. The essential attributes of the facility have not changed; the |
| 934 | interface allows trace functions to be installed per-thread, and the basic |
| 935 | events reported to the trace function are the same as had been reported to the |
| 936 | Python-level trace functions in previous versions. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 937 | |
| 938 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 939 | .. 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] | 940 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 941 | The type of the trace function registered using :c:func:`PyEval_SetProfile` and |
| 942 | :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] | 943 | registration function as *obj*, *frame* is the frame object to which the event |
| 944 | pertains, *what* is one of the constants :const:`PyTrace_CALL`, |
| 945 | :const:`PyTrace_EXCEPTION`, :const:`PyTrace_LINE`, :const:`PyTrace_RETURN`, |
| 946 | :const:`PyTrace_C_CALL`, :const:`PyTrace_C_EXCEPTION`, or |
| 947 | :const:`PyTrace_C_RETURN`, and *arg* depends on the value of *what*: |
| 948 | |
| 949 | +------------------------------+--------------------------------------+ |
| 950 | | Value of *what* | Meaning of *arg* | |
| 951 | +==============================+======================================+ |
| 952 | | :const:`PyTrace_CALL` | Always *NULL*. | |
| 953 | +------------------------------+--------------------------------------+ |
| 954 | | :const:`PyTrace_EXCEPTION` | Exception information as returned by | |
| 955 | | | :func:`sys.exc_info`. | |
| 956 | +------------------------------+--------------------------------------+ |
| 957 | | :const:`PyTrace_LINE` | Always *NULL*. | |
| 958 | +------------------------------+--------------------------------------+ |
Georg Brandl | d0b0e1d | 2010-10-15 16:42:37 +0000 | [diff] [blame] | 959 | | :const:`PyTrace_RETURN` | Value being returned to the caller, | |
| 960 | | | or *NULL* if caused by an exception. | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 961 | +------------------------------+--------------------------------------+ |
Georg Brandl | d0b0e1d | 2010-10-15 16:42:37 +0000 | [diff] [blame] | 962 | | :const:`PyTrace_C_CALL` | Function object being called. | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 963 | +------------------------------+--------------------------------------+ |
Georg Brandl | d0b0e1d | 2010-10-15 16:42:37 +0000 | [diff] [blame] | 964 | | :const:`PyTrace_C_EXCEPTION` | Function object being called. | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 965 | +------------------------------+--------------------------------------+ |
Georg Brandl | d0b0e1d | 2010-10-15 16:42:37 +0000 | [diff] [blame] | 966 | | :const:`PyTrace_C_RETURN` | Function object being called. | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 967 | +------------------------------+--------------------------------------+ |
| 968 | |
| 969 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 970 | .. c:var:: int PyTrace_CALL |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 971 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 972 | 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] | 973 | call to a function or method is being reported, or a new entry into a generator. |
| 974 | Note that the creation of the iterator for a generator function is not reported |
| 975 | as there is no control transfer to the Python bytecode in the corresponding |
| 976 | frame. |
| 977 | |
| 978 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 979 | .. c:var:: int PyTrace_EXCEPTION |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 980 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 981 | 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] | 982 | exception has been raised. The callback function is called with this value for |
| 983 | *what* when after any bytecode is processed after which the exception becomes |
| 984 | set within the frame being executed. The effect of this is that as exception |
| 985 | propagation causes the Python stack to unwind, the callback is called upon |
| 986 | return to each frame as the exception propagates. Only trace functions receives |
| 987 | these events; they are not needed by the profiler. |
| 988 | |
| 989 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 990 | .. c:var:: int PyTrace_LINE |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 991 | |
| 992 | The value passed as the *what* parameter to a trace function (but not a |
| 993 | profiling function) when a line-number event is being reported. |
| 994 | |
| 995 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 996 | .. c:var:: int PyTrace_RETURN |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 997 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 998 | 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] | 999 | call is returning without propagating an exception. |
| 1000 | |
| 1001 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 1002 | .. c:var:: int PyTrace_C_CALL |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 1003 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 1004 | 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] | 1005 | function is about to be called. |
| 1006 | |
| 1007 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 1008 | .. c:var:: int PyTrace_C_EXCEPTION |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 1009 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 1010 | 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] | 1011 | function has raised an exception. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 1012 | |
| 1013 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 1014 | .. c:var:: int PyTrace_C_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 C |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 1017 | function has returned. |
| 1018 | |
| 1019 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 1020 | .. c:function:: void PyEval_SetProfile(Py_tracefunc func, PyObject *obj) |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 1021 | |
| 1022 | Set the profiler function to *func*. The *obj* parameter is passed to the |
| 1023 | function as its first parameter, and may be any Python object, or *NULL*. If |
| 1024 | the profile function needs to maintain state, using a different value for *obj* |
| 1025 | for each thread provides a convenient and thread-safe place to store it. The |
| 1026 | profile function is called for all monitored events except the line-number |
| 1027 | events. |
| 1028 | |
| 1029 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 1030 | .. c:function:: void PyEval_SetTrace(Py_tracefunc func, PyObject *obj) |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 1031 | |
| 1032 | Set the tracing function to *func*. This is similar to |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 1033 | :c:func:`PyEval_SetProfile`, except the tracing function does receive line-number |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 1034 | events. |
| 1035 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 1036 | .. c:function:: PyObject* PyEval_GetCallStats(PyObject *self) |
Christian Heimes | d8654cf | 2007-12-02 15:22:16 +0000 | [diff] [blame] | 1037 | |
| 1038 | Return a tuple of function call counts. There are constants defined for the |
| 1039 | positions within the tuple: |
Georg Brandl | 48310cd | 2009-01-03 21:18:54 +0000 | [diff] [blame] | 1040 | |
Christian Heimes | d8654cf | 2007-12-02 15:22:16 +0000 | [diff] [blame] | 1041 | +-------------------------------+-------+ |
| 1042 | | Name | Value | |
| 1043 | +===============================+=======+ |
| 1044 | | :const:`PCALL_ALL` | 0 | |
| 1045 | +-------------------------------+-------+ |
| 1046 | | :const:`PCALL_FUNCTION` | 1 | |
| 1047 | +-------------------------------+-------+ |
| 1048 | | :const:`PCALL_FAST_FUNCTION` | 2 | |
| 1049 | +-------------------------------+-------+ |
| 1050 | | :const:`PCALL_FASTER_FUNCTION`| 3 | |
| 1051 | +-------------------------------+-------+ |
| 1052 | | :const:`PCALL_METHOD` | 4 | |
| 1053 | +-------------------------------+-------+ |
| 1054 | | :const:`PCALL_BOUND_METHOD` | 5 | |
| 1055 | +-------------------------------+-------+ |
| 1056 | | :const:`PCALL_CFUNCTION` | 6 | |
| 1057 | +-------------------------------+-------+ |
| 1058 | | :const:`PCALL_TYPE` | 7 | |
| 1059 | +-------------------------------+-------+ |
| 1060 | | :const:`PCALL_GENERATOR` | 8 | |
| 1061 | +-------------------------------+-------+ |
| 1062 | | :const:`PCALL_OTHER` | 9 | |
| 1063 | +-------------------------------+-------+ |
| 1064 | | :const:`PCALL_POP` | 10 | |
| 1065 | +-------------------------------+-------+ |
Georg Brandl | 48310cd | 2009-01-03 21:18:54 +0000 | [diff] [blame] | 1066 | |
Christian Heimes | d8654cf | 2007-12-02 15:22:16 +0000 | [diff] [blame] | 1067 | :const:`PCALL_FAST_FUNCTION` means no argument tuple needs to be created. |
| 1068 | :const:`PCALL_FASTER_FUNCTION` means that the fast-path frame setup code is used. |
| 1069 | |
| 1070 | If there is a method call where the call can be optimized by changing |
| 1071 | the argument tuple and calling the function directly, it gets recorded |
| 1072 | twice. |
| 1073 | |
| 1074 | This function is only present if Python is compiled with :const:`CALL_PROFILE` |
| 1075 | defined. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 1076 | |
| 1077 | .. _advanced-debugging: |
| 1078 | |
| 1079 | Advanced Debugger Support |
| 1080 | ========================= |
| 1081 | |
| 1082 | .. sectionauthor:: Fred L. Drake, Jr. <fdrake@acm.org> |
| 1083 | |
| 1084 | |
| 1085 | These functions are only intended to be used by advanced debugging tools. |
| 1086 | |
| 1087 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 1088 | .. c:function:: PyInterpreterState* PyInterpreterState_Head() |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 1089 | |
| 1090 | Return the interpreter state object at the head of the list of all such objects. |
| 1091 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 1092 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 1093 | .. c:function:: PyInterpreterState* PyInterpreterState_Next(PyInterpreterState *interp) |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 1094 | |
| 1095 | Return the next interpreter state object after *interp* from the list of all |
| 1096 | such objects. |
| 1097 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 1098 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 1099 | .. c:function:: PyThreadState * PyInterpreterState_ThreadHead(PyInterpreterState *interp) |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 1100 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 1101 | 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] | 1102 | threads associated with the interpreter *interp*. |
| 1103 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 1104 | |
Georg Brandl | 60203b4 | 2010-10-06 10:11:56 +0000 | [diff] [blame] | 1105 | .. c:function:: PyThreadState* PyThreadState_Next(PyThreadState *tstate) |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 1106 | |
| 1107 | 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] | 1108 | objects belonging to the same :c:type:`PyInterpreterState` object. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 1109 | |