Brett Cannon | afccd63 | 2009-01-20 02:21:27 +0000 | [diff] [blame] | 1 | :mod:`importlib` -- An implementation of :keyword:`import` |
| 2 | ========================================================== |
| 3 | |
| 4 | .. module:: importlib |
| 5 | :synopsis: An implementation of the import machinery. |
| 6 | |
| 7 | .. moduleauthor:: Brett Cannon <brett@python.org> |
| 8 | .. sectionauthor:: Brett Cannon <brett@python.org> |
| 9 | |
| 10 | .. versionadded:: 3.1 |
| 11 | |
| 12 | |
| 13 | Introduction |
| 14 | ------------ |
| 15 | |
| 16 | The purpose of the :mod:`importlib` package is two-fold. One is to provide an |
| 17 | implementation of the :keyword:`import` statement (and thus, by extension, the |
| 18 | :func:`__import__` function) in Python source code. This provides an |
Tarek Ziadé | 434caaa | 2009-05-14 12:48:09 +0000 | [diff] [blame] | 19 | implementation of :keyword:`import` which is portable to any Python |
Brett Cannon | afccd63 | 2009-01-20 02:21:27 +0000 | [diff] [blame] | 20 | interpreter. This also provides a reference implementation which is easier to |
Brett Cannon | f23e374 | 2010-06-27 23:57:46 +0000 | [diff] [blame] | 21 | comprehend than one implemented in a programming language other than Python. |
Brett Cannon | afccd63 | 2009-01-20 02:21:27 +0000 | [diff] [blame] | 22 | |
Brett Cannon | f23e374 | 2010-06-27 23:57:46 +0000 | [diff] [blame] | 23 | Two, the components to implement :keyword:`import` are exposed in this |
Brett Cannon | afccd63 | 2009-01-20 02:21:27 +0000 | [diff] [blame] | 24 | package, making it easier for users to create their own custom objects (known |
Brett Cannon | debb98d | 2009-02-16 04:18:01 +0000 | [diff] [blame] | 25 | generically as an :term:`importer`) to participate in the import process. |
Brett Cannon | f23e374 | 2010-06-27 23:57:46 +0000 | [diff] [blame] | 26 | Details on custom importers can be found in :pep:`302`. |
Brett Cannon | afccd63 | 2009-01-20 02:21:27 +0000 | [diff] [blame] | 27 | |
| 28 | .. seealso:: |
| 29 | |
| 30 | :ref:`import` |
| 31 | The language reference for the :keyword:`import` statement. |
| 32 | |
| 33 | `Packages specification <http://www.python.org/doc/essays/packages.html>`__ |
| 34 | Original specification of packages. Some semantics have changed since |
Georg Brandl | 375aec2 | 2011-01-15 17:03:02 +0000 | [diff] [blame] | 35 | the writing of this document (e.g. redirecting based on ``None`` |
Brett Cannon | afccd63 | 2009-01-20 02:21:27 +0000 | [diff] [blame] | 36 | in :data:`sys.modules`). |
| 37 | |
| 38 | The :func:`.__import__` function |
Brett Cannon | 0e13c94 | 2010-06-29 18:26:11 +0000 | [diff] [blame] | 39 | The :keyword:`import` statement is syntactic sugar for this function. |
Brett Cannon | afccd63 | 2009-01-20 02:21:27 +0000 | [diff] [blame] | 40 | |
| 41 | :pep:`235` |
| 42 | Import on Case-Insensitive Platforms |
| 43 | |
| 44 | :pep:`263` |
| 45 | Defining Python Source Code Encodings |
| 46 | |
| 47 | :pep:`302` |
Brett Cannon | f23e374 | 2010-06-27 23:57:46 +0000 | [diff] [blame] | 48 | New Import Hooks |
Brett Cannon | afccd63 | 2009-01-20 02:21:27 +0000 | [diff] [blame] | 49 | |
| 50 | :pep:`328` |
| 51 | Imports: Multi-Line and Absolute/Relative |
| 52 | |
| 53 | :pep:`366` |
| 54 | Main module explicit relative imports |
| 55 | |
Brett Cannon | 8917d5e | 2010-01-13 19:21:00 +0000 | [diff] [blame] | 56 | :pep:`3120` |
Brett Cannon | afccd63 | 2009-01-20 02:21:27 +0000 | [diff] [blame] | 57 | Using UTF-8 as the Default Source Encoding |
| 58 | |
Brett Cannon | 30b7a90 | 2010-06-27 21:49:22 +0000 | [diff] [blame] | 59 | :pep:`3147` |
| 60 | PYC Repository Directories |
| 61 | |
Brett Cannon | afccd63 | 2009-01-20 02:21:27 +0000 | [diff] [blame] | 62 | |
| 63 | Functions |
| 64 | --------- |
| 65 | |
Brett Cannon | 78246b6 | 2009-01-25 04:56:30 +0000 | [diff] [blame] | 66 | .. function:: __import__(name, globals={}, locals={}, fromlist=list(), level=0) |
Brett Cannon | afccd63 | 2009-01-20 02:21:27 +0000 | [diff] [blame] | 67 | |
Brett Cannon | f23e374 | 2010-06-27 23:57:46 +0000 | [diff] [blame] | 68 | An implementation of the built-in :func:`__import__` function. |
Brett Cannon | afccd63 | 2009-01-20 02:21:27 +0000 | [diff] [blame] | 69 | |
| 70 | .. function:: import_module(name, package=None) |
| 71 | |
Brett Cannon | 33418c8 | 2009-01-22 18:37:20 +0000 | [diff] [blame] | 72 | Import a module. The *name* argument specifies what module to |
Brett Cannon | afccd63 | 2009-01-20 02:21:27 +0000 | [diff] [blame] | 73 | import in absolute or relative terms |
| 74 | (e.g. either ``pkg.mod`` or ``..mod``). If the name is |
Guido van Rossum | 0961354 | 2009-03-30 20:34:57 +0000 | [diff] [blame] | 75 | specified in relative terms, then the *package* argument must be set to |
| 76 | the name of the package which is to act as the anchor for resolving the |
Brett Cannon | afccd63 | 2009-01-20 02:21:27 +0000 | [diff] [blame] | 77 | package name (e.g. ``import_module('..mod', 'pkg.subpkg')`` will import |
Brett Cannon | 2c318a1 | 2009-02-07 01:15:27 +0000 | [diff] [blame] | 78 | ``pkg.mod``). |
Brett Cannon | 78246b6 | 2009-01-25 04:56:30 +0000 | [diff] [blame] | 79 | |
Brett Cannon | 2c318a1 | 2009-02-07 01:15:27 +0000 | [diff] [blame] | 80 | The :func:`import_module` function acts as a simplifying wrapper around |
Brett Cannon | 9f4cb1c | 2009-04-01 23:26:47 +0000 | [diff] [blame] | 81 | :func:`importlib.__import__`. This means all semantics of the function are |
| 82 | derived from :func:`importlib.__import__`, including requiring the package |
| 83 | from which an import is occurring to have been previously imported |
| 84 | (i.e., *package* must already be imported). The most important difference |
| 85 | is that :func:`import_module` returns the most nested package or module |
| 86 | that was imported (e.g. ``pkg.mod``), while :func:`__import__` returns the |
Guido van Rossum | 0961354 | 2009-03-30 20:34:57 +0000 | [diff] [blame] | 87 | top-level package or module (e.g. ``pkg``). |
| 88 | |
Brett Cannon | 78246b6 | 2009-01-25 04:56:30 +0000 | [diff] [blame] | 89 | |
Brett Cannon | 2a922ed | 2009-03-09 03:35:50 +0000 | [diff] [blame] | 90 | :mod:`importlib.abc` -- Abstract base classes related to import |
| 91 | --------------------------------------------------------------- |
| 92 | |
| 93 | .. module:: importlib.abc |
| 94 | :synopsis: Abstract base classes related to import |
| 95 | |
| 96 | The :mod:`importlib.abc` module contains all of the core abstract base classes |
| 97 | used by :keyword:`import`. Some subclasses of the core abstract base classes |
| 98 | are also provided to help in implementing the core ABCs. |
| 99 | |
| 100 | |
| 101 | .. class:: Finder |
| 102 | |
| 103 | An abstract base class representing a :term:`finder`. |
Guido van Rossum | 0961354 | 2009-03-30 20:34:57 +0000 | [diff] [blame] | 104 | See :pep:`302` for the exact definition for a finder. |
Brett Cannon | 2a922ed | 2009-03-09 03:35:50 +0000 | [diff] [blame] | 105 | |
Brett Cannon | 9c751b7 | 2009-03-09 16:28:16 +0000 | [diff] [blame] | 106 | .. method:: find_module(fullname, path=None) |
Brett Cannon | 2a922ed | 2009-03-09 03:35:50 +0000 | [diff] [blame] | 107 | |
| 108 | An abstract method for finding a :term:`loader` for the specified |
| 109 | module. If the :term:`finder` is found on :data:`sys.meta_path` and the |
Guido van Rossum | 0961354 | 2009-03-30 20:34:57 +0000 | [diff] [blame] | 110 | module to be searched for is a subpackage or module then *path* will |
| 111 | be the value of :attr:`__path__` from the parent package. If a loader |
Georg Brandl | 375aec2 | 2011-01-15 17:03:02 +0000 | [diff] [blame] | 112 | cannot be found, ``None`` is returned. |
Brett Cannon | 2a922ed | 2009-03-09 03:35:50 +0000 | [diff] [blame] | 113 | |
Brett Cannon | 2a922ed | 2009-03-09 03:35:50 +0000 | [diff] [blame] | 114 | |
| 115 | .. class:: Loader |
| 116 | |
| 117 | An abstract base class for a :term:`loader`. |
Guido van Rossum | 0961354 | 2009-03-30 20:34:57 +0000 | [diff] [blame] | 118 | See :pep:`302` for the exact definition for a loader. |
Brett Cannon | 2a922ed | 2009-03-09 03:35:50 +0000 | [diff] [blame] | 119 | |
Brett Cannon | 9c751b7 | 2009-03-09 16:28:16 +0000 | [diff] [blame] | 120 | .. method:: load_module(fullname) |
Brett Cannon | 2a922ed | 2009-03-09 03:35:50 +0000 | [diff] [blame] | 121 | |
| 122 | An abstract method for loading a module. If the module cannot be |
| 123 | loaded, :exc:`ImportError` is raised, otherwise the loaded module is |
| 124 | returned. |
| 125 | |
Guido van Rossum | 0961354 | 2009-03-30 20:34:57 +0000 | [diff] [blame] | 126 | If the requested module already exists in :data:`sys.modules`, that |
Brett Cannon | 2a922ed | 2009-03-09 03:35:50 +0000 | [diff] [blame] | 127 | module should be used and reloaded. |
Guido van Rossum | 0961354 | 2009-03-30 20:34:57 +0000 | [diff] [blame] | 128 | Otherwise the loader should create a new module and insert it into |
| 129 | :data:`sys.modules` before any loading begins, to prevent recursion |
| 130 | from the import. If the loader inserted a module and the load fails, it |
Brett Cannon | 2a922ed | 2009-03-09 03:35:50 +0000 | [diff] [blame] | 131 | must be removed by the loader from :data:`sys.modules`; modules already |
| 132 | in :data:`sys.modules` before the loader began execution should be left |
| 133 | alone. The :func:`importlib.util.module_for_loader` decorator handles |
| 134 | all of these details. |
| 135 | |
Guido van Rossum | 0961354 | 2009-03-30 20:34:57 +0000 | [diff] [blame] | 136 | The loader should set several attributes on the module. |
| 137 | (Note that some of these attributes can change when a module is |
| 138 | reloaded.) |
Brett Cannon | 2a922ed | 2009-03-09 03:35:50 +0000 | [diff] [blame] | 139 | |
| 140 | - :attr:`__name__` |
| 141 | The name of the module. |
| 142 | |
| 143 | - :attr:`__file__` |
| 144 | The path to where the module data is stored (not set for built-in |
| 145 | modules). |
| 146 | |
| 147 | - :attr:`__path__` |
Guido van Rossum | 0961354 | 2009-03-30 20:34:57 +0000 | [diff] [blame] | 148 | A list of strings specifying the search path within a |
Brett Cannon | 2a922ed | 2009-03-09 03:35:50 +0000 | [diff] [blame] | 149 | package. This attribute is not set on modules. |
| 150 | |
| 151 | - :attr:`__package__` |
| 152 | The parent package for the module/package. If the module is |
| 153 | top-level then it has a value of the empty string. The |
| 154 | :func:`importlib.util.set_package` decorator can handle the details |
| 155 | for :attr:`__package__`. |
| 156 | |
| 157 | - :attr:`__loader__` |
Guido van Rossum | 0961354 | 2009-03-30 20:34:57 +0000 | [diff] [blame] | 158 | The loader used to load the module. |
| 159 | (This is not set by the built-in import machinery, |
| 160 | but it should be set whenever a :term:`loader` is used.) |
Brett Cannon | 2a922ed | 2009-03-09 03:35:50 +0000 | [diff] [blame] | 161 | |
| 162 | |
| 163 | .. class:: ResourceLoader |
| 164 | |
| 165 | An abstract base class for a :term:`loader` which implements the optional |
| 166 | :pep:`302` protocol for loading arbitrary resources from the storage |
| 167 | back-end. |
| 168 | |
Brett Cannon | 9c751b7 | 2009-03-09 16:28:16 +0000 | [diff] [blame] | 169 | .. method:: get_data(path) |
Brett Cannon | 2a922ed | 2009-03-09 03:35:50 +0000 | [diff] [blame] | 170 | |
| 171 | An abstract method to return the bytes for the data located at *path*. |
Guido van Rossum | 0961354 | 2009-03-30 20:34:57 +0000 | [diff] [blame] | 172 | Loaders that have a file-like storage back-end |
Brett Cannon | 16248a4 | 2009-04-01 20:47:14 +0000 | [diff] [blame] | 173 | that allows storing arbitrary data |
Guido van Rossum | 0961354 | 2009-03-30 20:34:57 +0000 | [diff] [blame] | 174 | can implement this abstract method to give direct access |
Brett Cannon | 2a922ed | 2009-03-09 03:35:50 +0000 | [diff] [blame] | 175 | to the data stored. :exc:`IOError` is to be raised if the *path* cannot |
| 176 | be found. The *path* is expected to be constructed using a module's |
Brett Cannon | 16248a4 | 2009-04-01 20:47:14 +0000 | [diff] [blame] | 177 | :attr:`__file__` attribute or an item from a package's :attr:`__path__`. |
Brett Cannon | 2a922ed | 2009-03-09 03:35:50 +0000 | [diff] [blame] | 178 | |
| 179 | |
| 180 | .. class:: InspectLoader |
| 181 | |
| 182 | An abstract base class for a :term:`loader` which implements the optional |
Guido van Rossum | 0961354 | 2009-03-30 20:34:57 +0000 | [diff] [blame] | 183 | :pep:`302` protocol for loaders that inspect modules. |
Brett Cannon | 2a922ed | 2009-03-09 03:35:50 +0000 | [diff] [blame] | 184 | |
Brett Cannon | a113ac5 | 2009-03-15 01:41:33 +0000 | [diff] [blame] | 185 | .. method:: get_code(fullname) |
Brett Cannon | 2a922ed | 2009-03-09 03:35:50 +0000 | [diff] [blame] | 186 | |
Brett Cannon | a113ac5 | 2009-03-15 01:41:33 +0000 | [diff] [blame] | 187 | An abstract method to return the :class:`code` object for a module. |
Georg Brandl | 375aec2 | 2011-01-15 17:03:02 +0000 | [diff] [blame] | 188 | ``None`` is returned if the module does not have a code object |
Brett Cannon | a113ac5 | 2009-03-15 01:41:33 +0000 | [diff] [blame] | 189 | (e.g. built-in module). :exc:`ImportError` is raised if loader cannot |
| 190 | find the requested module. |
Brett Cannon | 2a922ed | 2009-03-09 03:35:50 +0000 | [diff] [blame] | 191 | |
Brett Cannon | 9c751b7 | 2009-03-09 16:28:16 +0000 | [diff] [blame] | 192 | .. method:: get_source(fullname) |
Brett Cannon | 2a922ed | 2009-03-09 03:35:50 +0000 | [diff] [blame] | 193 | |
| 194 | An abstract method to return the source of a module. It is returned as |
Georg Brandl | 375aec2 | 2011-01-15 17:03:02 +0000 | [diff] [blame] | 195 | a text string with universal newlines. Returns ``None`` if no |
Brett Cannon | 2a922ed | 2009-03-09 03:35:50 +0000 | [diff] [blame] | 196 | source is available (e.g. a built-in module). Raises :exc:`ImportError` |
| 197 | if the loader cannot find the module specified. |
| 198 | |
Brett Cannon | a113ac5 | 2009-03-15 01:41:33 +0000 | [diff] [blame] | 199 | .. method:: is_package(fullname) |
Brett Cannon | 2a922ed | 2009-03-09 03:35:50 +0000 | [diff] [blame] | 200 | |
Brett Cannon | a113ac5 | 2009-03-15 01:41:33 +0000 | [diff] [blame] | 201 | An abstract method to return a true value if the module is a package, a |
| 202 | false value otherwise. :exc:`ImportError` is raised if the |
| 203 | :term:`loader` cannot find the module. |
Brett Cannon | 2a922ed | 2009-03-09 03:35:50 +0000 | [diff] [blame] | 204 | |
| 205 | |
Brett Cannon | 6919427 | 2009-07-20 04:23:48 +0000 | [diff] [blame] | 206 | .. class:: ExecutionLoader |
| 207 | |
| 208 | An abstract base class which inherits from :class:`InspectLoader` that, |
Brett Cannon | 2346029 | 2009-07-20 22:59:00 +0000 | [diff] [blame] | 209 | when implemented, helps a module to be executed as a script. The ABC |
Brett Cannon | 6919427 | 2009-07-20 04:23:48 +0000 | [diff] [blame] | 210 | represents an optional :pep:`302` protocol. |
| 211 | |
| 212 | .. method:: get_filename(fullname) |
| 213 | |
Brett Cannon | f23e374 | 2010-06-27 23:57:46 +0000 | [diff] [blame] | 214 | An abstract method that is to return the value of :attr:`__file__` for |
Brett Cannon | 6919427 | 2009-07-20 04:23:48 +0000 | [diff] [blame] | 215 | the specified module. If no path is available, :exc:`ImportError` is |
| 216 | raised. |
| 217 | |
Brett Cannon | f23e374 | 2010-06-27 23:57:46 +0000 | [diff] [blame] | 218 | If source code is available, then the method should return the path to |
| 219 | the source file, regardless of whether a bytecode was used to load the |
| 220 | module. |
| 221 | |
| 222 | |
| 223 | .. class:: SourceLoader |
| 224 | |
| 225 | An abstract base class for implementing source (and optionally bytecode) |
| 226 | file loading. The class inherits from both :class:`ResourceLoader` and |
| 227 | :class:`ExecutionLoader`, requiring the implementation of: |
| 228 | |
| 229 | * :meth:`ResourceLoader.get_data` |
| 230 | * :meth:`ExecutionLoader.get_filename` |
Brett Cannon | 6dfbff3 | 2010-07-21 09:48:31 +0000 | [diff] [blame] | 231 | Should only return the path to the source file; sourceless |
Brett Cannon | f23e374 | 2010-06-27 23:57:46 +0000 | [diff] [blame] | 232 | loading is not supported. |
| 233 | |
| 234 | The abstract methods defined by this class are to add optional bytecode |
| 235 | file support. Not implementing these optional methods causes the loader to |
| 236 | only work with source code. Implementing the methods allows the loader to |
| 237 | work with source *and* bytecode files; it does not allow for *sourceless* |
| 238 | loading where only bytecode is provided. Bytecode files are an |
| 239 | optimization to speed up loading by removing the parsing step of Python's |
| 240 | compiler, and so no bytecode-specific API is exposed. |
| 241 | |
| 242 | .. method:: path_mtime(self, path) |
| 243 | |
| 244 | Optional abstract method which returns the modification time for the |
| 245 | specified path. |
| 246 | |
| 247 | .. method:: set_data(self, path, data) |
| 248 | |
| 249 | Optional abstract method which writes the specified bytes to a file |
Brett Cannon | 61b1425 | 2010-07-03 21:48:25 +0000 | [diff] [blame] | 250 | path. Any intermediate directories which do not exist are to be created |
| 251 | automatically. |
| 252 | |
| 253 | When writing to the path fails because the path is read-only |
| 254 | (:attr:`errno.EACCES`), do not propagate the exception. |
Brett Cannon | f23e374 | 2010-06-27 23:57:46 +0000 | [diff] [blame] | 255 | |
| 256 | .. method:: get_code(self, fullname) |
| 257 | |
| 258 | Concrete implementation of :meth:`InspectLoader.get_code`. |
| 259 | |
| 260 | .. method:: load_module(self, fullname) |
| 261 | |
| 262 | Concrete implementation of :meth:`Loader.load_module`. |
| 263 | |
| 264 | .. method:: get_source(self, fullname) |
| 265 | |
| 266 | Concrete implementation of :meth:`InspectLoader.get_source`. |
| 267 | |
| 268 | .. method:: is_package(self, fullname) |
| 269 | |
| 270 | Concrete implementation of :meth:`InspectLoader.is_package`. A module |
| 271 | is determined to be a package if its file path is a file named |
| 272 | ``__init__`` when the file extension is removed. |
| 273 | |
Brett Cannon | 6919427 | 2009-07-20 04:23:48 +0000 | [diff] [blame] | 274 | |
Brett Cannon | 2a922ed | 2009-03-09 03:35:50 +0000 | [diff] [blame] | 275 | .. class:: PyLoader |
| 276 | |
Brett Cannon | 6919427 | 2009-07-20 04:23:48 +0000 | [diff] [blame] | 277 | An abstract base class inheriting from |
Brett Cannon | f23e374 | 2010-06-27 23:57:46 +0000 | [diff] [blame] | 278 | :class:`ExecutionLoader` and |
| 279 | :class:`ResourceLoader` designed to ease the loading of |
Brett Cannon | 2a922ed | 2009-03-09 03:35:50 +0000 | [diff] [blame] | 280 | Python source modules (bytecode is not handled; see |
Brett Cannon | f23e374 | 2010-06-27 23:57:46 +0000 | [diff] [blame] | 281 | :class:`SourceLoader` for a source/bytecode ABC). A subclass |
Brett Cannon | 2a922ed | 2009-03-09 03:35:50 +0000 | [diff] [blame] | 282 | implementing this ABC will only need to worry about exposing how the source |
| 283 | code is stored; all other details for loading Python source code will be |
| 284 | handled by the concrete implementations of key methods. |
| 285 | |
Brett Cannon | f23e374 | 2010-06-27 23:57:46 +0000 | [diff] [blame] | 286 | .. deprecated:: 3.2 |
| 287 | This class has been deprecated in favor of :class:`SourceLoader` and is |
| 288 | slated for removal in Python 3.4. See below for how to create a |
Georg Brandl | 6faee4e | 2010-09-21 14:48:28 +0000 | [diff] [blame] | 289 | subclass that is compatible with Python 3.1 onwards. |
Brett Cannon | f23e374 | 2010-06-27 23:57:46 +0000 | [diff] [blame] | 290 | |
| 291 | If compatibility with Python 3.1 is required, then use the following idiom |
| 292 | to implement a subclass that will work with Python 3.1 onwards (make sure |
| 293 | to implement :meth:`ExecutionLoader.get_filename`):: |
| 294 | |
| 295 | try: |
| 296 | from importlib.abc import SourceLoader |
| 297 | except ImportError: |
| 298 | from importlib.abc import PyLoader as SourceLoader |
| 299 | |
| 300 | |
| 301 | class CustomLoader(SourceLoader): |
| 302 | def get_filename(self, fullname): |
| 303 | """Return the path to the source file.""" |
| 304 | # Implement ... |
| 305 | |
| 306 | def source_path(self, fullname): |
| 307 | """Implement source_path in terms of get_filename.""" |
| 308 | try: |
| 309 | return self.get_filename(fullname) |
| 310 | except ImportError: |
| 311 | return None |
| 312 | |
| 313 | def is_package(self, fullname): |
| 314 | """Implement is_package by looking for an __init__ file |
| 315 | name as returned by get_filename.""" |
| 316 | filename = os.path.basename(self.get_filename(fullname)) |
| 317 | return os.path.splitext(filename)[0] == '__init__' |
| 318 | |
| 319 | |
Brett Cannon | 9c751b7 | 2009-03-09 16:28:16 +0000 | [diff] [blame] | 320 | .. method:: source_path(fullname) |
Brett Cannon | 2a922ed | 2009-03-09 03:35:50 +0000 | [diff] [blame] | 321 | |
| 322 | An abstract method that returns the path to the source code for a |
Georg Brandl | 375aec2 | 2011-01-15 17:03:02 +0000 | [diff] [blame] | 323 | module. Should return ``None`` if there is no source code. |
Brett Cannon | 3e761a9 | 2009-12-10 00:24:21 +0000 | [diff] [blame] | 324 | Raises :exc:`ImportError` if the loader knows it cannot handle the |
| 325 | module. |
Brett Cannon | 2a922ed | 2009-03-09 03:35:50 +0000 | [diff] [blame] | 326 | |
Brett Cannon | 6919427 | 2009-07-20 04:23:48 +0000 | [diff] [blame] | 327 | .. method:: get_filename(fullname) |
| 328 | |
| 329 | A concrete implementation of |
| 330 | :meth:`importlib.abc.ExecutionLoader.get_filename` that |
| 331 | relies on :meth:`source_path`. If :meth:`source_path` returns |
Georg Brandl | 375aec2 | 2011-01-15 17:03:02 +0000 | [diff] [blame] | 332 | ``None``, then :exc:`ImportError` is raised. |
Brett Cannon | 6919427 | 2009-07-20 04:23:48 +0000 | [diff] [blame] | 333 | |
Brett Cannon | 9c751b7 | 2009-03-09 16:28:16 +0000 | [diff] [blame] | 334 | .. method:: load_module(fullname) |
Brett Cannon | 2a922ed | 2009-03-09 03:35:50 +0000 | [diff] [blame] | 335 | |
| 336 | A concrete implementation of :meth:`importlib.abc.Loader.load_module` |
Brett Cannon | ad876c7 | 2009-03-09 07:53:09 +0000 | [diff] [blame] | 337 | that loads Python source code. All needed information comes from the |
| 338 | abstract methods required by this ABC. The only pertinent assumption |
| 339 | made by this method is that when loading a package |
| 340 | :attr:`__path__` is set to ``[os.path.dirname(__file__)]``. |
Brett Cannon | 2a922ed | 2009-03-09 03:35:50 +0000 | [diff] [blame] | 341 | |
Brett Cannon | 9c751b7 | 2009-03-09 16:28:16 +0000 | [diff] [blame] | 342 | .. method:: get_code(fullname) |
Brett Cannon | 2a922ed | 2009-03-09 03:35:50 +0000 | [diff] [blame] | 343 | |
| 344 | A concrete implementation of |
| 345 | :meth:`importlib.abc.InspectLoader.get_code` that creates code objects |
Guido van Rossum | 0961354 | 2009-03-30 20:34:57 +0000 | [diff] [blame] | 346 | from Python source code, by requesting the source code (using |
Benjamin Peterson | 0089d75 | 2009-11-13 00:52:43 +0000 | [diff] [blame] | 347 | :meth:`source_path` and :meth:`get_data`) and compiling it with the |
| 348 | built-in :func:`compile` function. |
Brett Cannon | 2a922ed | 2009-03-09 03:35:50 +0000 | [diff] [blame] | 349 | |
Brett Cannon | d43b30b | 2009-03-10 03:29:23 +0000 | [diff] [blame] | 350 | .. method:: get_source(fullname) |
| 351 | |
| 352 | A concrete implementation of |
| 353 | :meth:`importlib.abc.InspectLoader.get_source`. Uses |
Brett Cannon | 6919427 | 2009-07-20 04:23:48 +0000 | [diff] [blame] | 354 | :meth:`importlib.abc.ResourceLoader.get_data` and :meth:`source_path` |
| 355 | to get the source code. It tries to guess the source encoding using |
Guido van Rossum | 0961354 | 2009-03-30 20:34:57 +0000 | [diff] [blame] | 356 | :func:`tokenize.detect_encoding`. |
Brett Cannon | d43b30b | 2009-03-10 03:29:23 +0000 | [diff] [blame] | 357 | |
Brett Cannon | 2a922ed | 2009-03-09 03:35:50 +0000 | [diff] [blame] | 358 | |
| 359 | .. class:: PyPycLoader |
| 360 | |
Brett Cannon | f23e374 | 2010-06-27 23:57:46 +0000 | [diff] [blame] | 361 | An abstract base class inheriting from :class:`PyLoader`. |
Brett Cannon | 2a922ed | 2009-03-09 03:35:50 +0000 | [diff] [blame] | 362 | This ABC is meant to help in creating loaders that support both Python |
| 363 | source and bytecode. |
| 364 | |
Brett Cannon | f23e374 | 2010-06-27 23:57:46 +0000 | [diff] [blame] | 365 | .. deprecated:: 3.2 |
| 366 | This class has been deprecated in favor of :class:`SourceLoader` and to |
| 367 | properly support :pep:`3147`. If compatibility is required with |
| 368 | Python 3.1, implement both :class:`SourceLoader` and :class:`PyLoader`; |
| 369 | instructions on how to do so are included in the documentation for |
| 370 | :class:`PyLoader`. Do note that this solution will not support |
| 371 | sourceless/bytecode-only loading; only source *and* bytecode loading. |
| 372 | |
Brett Cannon | 9c751b7 | 2009-03-09 16:28:16 +0000 | [diff] [blame] | 373 | .. method:: source_mtime(fullname) |
Brett Cannon | 2a922ed | 2009-03-09 03:35:50 +0000 | [diff] [blame] | 374 | |
| 375 | An abstract method which returns the modification time for the source |
| 376 | code of the specified module. The modification time should be an |
Georg Brandl | 375aec2 | 2011-01-15 17:03:02 +0000 | [diff] [blame] | 377 | integer. If there is no source code, return ``None``. If the |
Brett Cannon | 2a922ed | 2009-03-09 03:35:50 +0000 | [diff] [blame] | 378 | module cannot be found then :exc:`ImportError` is raised. |
| 379 | |
Brett Cannon | 9c751b7 | 2009-03-09 16:28:16 +0000 | [diff] [blame] | 380 | .. method:: bytecode_path(fullname) |
Brett Cannon | 2a922ed | 2009-03-09 03:35:50 +0000 | [diff] [blame] | 381 | |
| 382 | An abstract method which returns the path to the bytecode for the |
Georg Brandl | 375aec2 | 2011-01-15 17:03:02 +0000 | [diff] [blame] | 383 | specified module, if it exists. It returns ``None`` |
Guido van Rossum | 0961354 | 2009-03-30 20:34:57 +0000 | [diff] [blame] | 384 | if no bytecode exists (yet). |
Brett Cannon | 3e761a9 | 2009-12-10 00:24:21 +0000 | [diff] [blame] | 385 | Raises :exc:`ImportError` if the loader knows it cannot handle the |
| 386 | module. |
Brett Cannon | 2a922ed | 2009-03-09 03:35:50 +0000 | [diff] [blame] | 387 | |
Brett Cannon | 6919427 | 2009-07-20 04:23:48 +0000 | [diff] [blame] | 388 | .. method:: get_filename(fullname) |
| 389 | |
| 390 | A concrete implementation of |
Brett Cannon | f23e374 | 2010-06-27 23:57:46 +0000 | [diff] [blame] | 391 | :meth:`ExecutionLoader.get_filename` that relies on |
| 392 | :meth:`PyLoader.source_path` and :meth:`bytecode_path`. |
Brett Cannon | 6919427 | 2009-07-20 04:23:48 +0000 | [diff] [blame] | 393 | If :meth:`source_path` returns a path, then that value is returned. |
| 394 | Else if :meth:`bytecode_path` returns a path, that path will be |
| 395 | returned. If a path is not available from both methods, |
| 396 | :exc:`ImportError` is raised. |
| 397 | |
Brett Cannon | 9c751b7 | 2009-03-09 16:28:16 +0000 | [diff] [blame] | 398 | .. method:: write_bytecode(fullname, bytecode) |
Brett Cannon | 2a922ed | 2009-03-09 03:35:50 +0000 | [diff] [blame] | 399 | |
| 400 | An abstract method which has the loader write *bytecode* for future |
Georg Brandl | 375aec2 | 2011-01-15 17:03:02 +0000 | [diff] [blame] | 401 | use. If the bytecode is written, return ``True``. Return |
| 402 | ``False`` if the bytecode could not be written. This method |
Brett Cannon | 2a922ed | 2009-03-09 03:35:50 +0000 | [diff] [blame] | 403 | should not be called if :data:`sys.dont_write_bytecode` is true. |
Guido van Rossum | 0961354 | 2009-03-30 20:34:57 +0000 | [diff] [blame] | 404 | The *bytecode* argument should be a bytes string or bytes array. |
Brett Cannon | 2a922ed | 2009-03-09 03:35:50 +0000 | [diff] [blame] | 405 | |
| 406 | |
Brett Cannon | 78246b6 | 2009-01-25 04:56:30 +0000 | [diff] [blame] | 407 | :mod:`importlib.machinery` -- Importers and path hooks |
| 408 | ------------------------------------------------------ |
| 409 | |
| 410 | .. module:: importlib.machinery |
| 411 | :synopsis: Importers and path hooks |
| 412 | |
| 413 | This module contains the various objects that help :keyword:`import` |
| 414 | find and load modules. |
| 415 | |
| 416 | .. class:: BuiltinImporter |
| 417 | |
Brett Cannon | 2a922ed | 2009-03-09 03:35:50 +0000 | [diff] [blame] | 418 | An :term:`importer` for built-in modules. All known built-in modules are |
| 419 | listed in :data:`sys.builtin_module_names`. This class implements the |
Brett Cannon | a113ac5 | 2009-03-15 01:41:33 +0000 | [diff] [blame] | 420 | :class:`importlib.abc.Finder` and :class:`importlib.abc.InspectLoader` |
| 421 | ABCs. |
Brett Cannon | 78246b6 | 2009-01-25 04:56:30 +0000 | [diff] [blame] | 422 | |
| 423 | Only class methods are defined by this class to alleviate the need for |
| 424 | instantiation. |
| 425 | |
Brett Cannon | 78246b6 | 2009-01-25 04:56:30 +0000 | [diff] [blame] | 426 | |
| 427 | .. class:: FrozenImporter |
| 428 | |
Brett Cannon | 2a922ed | 2009-03-09 03:35:50 +0000 | [diff] [blame] | 429 | An :term:`importer` for frozen modules. This class implements the |
Brett Cannon | 8d11013 | 2009-03-15 02:20:16 +0000 | [diff] [blame] | 430 | :class:`importlib.abc.Finder` and :class:`importlib.abc.InspectLoader` |
| 431 | ABCs. |
Brett Cannon | 78246b6 | 2009-01-25 04:56:30 +0000 | [diff] [blame] | 432 | |
| 433 | Only class methods are defined by this class to alleviate the need for |
| 434 | instantiation. |
| 435 | |
Brett Cannon | debb98d | 2009-02-16 04:18:01 +0000 | [diff] [blame] | 436 | |
| 437 | .. class:: PathFinder |
| 438 | |
Brett Cannon | 2a922ed | 2009-03-09 03:35:50 +0000 | [diff] [blame] | 439 | :term:`Finder` for :data:`sys.path`. This class implements the |
| 440 | :class:`importlib.abc.Finder` ABC. |
Brett Cannon | debb98d | 2009-02-16 04:18:01 +0000 | [diff] [blame] | 441 | |
| 442 | This class does not perfectly mirror the semantics of :keyword:`import` in |
| 443 | terms of :data:`sys.path`. No implicit path hooks are assumed for |
| 444 | simplification of the class and its semantics. |
| 445 | |
Brett Cannon | 1b184d5 | 2009-11-07 08:22:58 +0000 | [diff] [blame] | 446 | Only class methods are defined by this class to alleviate the need for |
Brett Cannon | debb98d | 2009-02-16 04:18:01 +0000 | [diff] [blame] | 447 | instantiation. |
| 448 | |
| 449 | .. classmethod:: find_module(fullname, path=None) |
| 450 | |
| 451 | Class method that attempts to find a :term:`loader` for the module |
Brett Cannon | 2a922ed | 2009-03-09 03:35:50 +0000 | [diff] [blame] | 452 | specified by *fullname* on :data:`sys.path` or, if defined, on |
Brett Cannon | debb98d | 2009-02-16 04:18:01 +0000 | [diff] [blame] | 453 | *path*. For each path entry that is searched, |
| 454 | :data:`sys.path_importer_cache` is checked. If an non-false object is |
Brett Cannon | 2a922ed | 2009-03-09 03:35:50 +0000 | [diff] [blame] | 455 | found then it is used as the :term:`finder` to look for the module |
| 456 | being searched for. If no entry is found in |
Brett Cannon | debb98d | 2009-02-16 04:18:01 +0000 | [diff] [blame] | 457 | :data:`sys.path_importer_cache`, then :data:`sys.path_hooks` is |
| 458 | searched for a finder for the path entry and, if found, is stored in |
| 459 | :data:`sys.path_importer_cache` along with being queried about the |
Georg Brandl | 375aec2 | 2011-01-15 17:03:02 +0000 | [diff] [blame] | 460 | module. If no finder is ever found then ``None`` is returned. |
Brett Cannon | d2e7b33 | 2009-02-17 02:45:03 +0000 | [diff] [blame] | 461 | |
| 462 | |
| 463 | :mod:`importlib.util` -- Utility code for importers |
| 464 | --------------------------------------------------- |
| 465 | |
| 466 | .. module:: importlib.util |
| 467 | :synopsis: Importers and path hooks |
| 468 | |
| 469 | This module contains the various objects that help in the construction of |
| 470 | an :term:`importer`. |
| 471 | |
Georg Brandl | 8a1caa2 | 2010-07-29 16:01:11 +0000 | [diff] [blame] | 472 | .. decorator:: module_for_loader |
Brett Cannon | d2e7b33 | 2009-02-17 02:45:03 +0000 | [diff] [blame] | 473 | |
Guido van Rossum | 0961354 | 2009-03-30 20:34:57 +0000 | [diff] [blame] | 474 | A :term:`decorator` for a :term:`loader` method, |
| 475 | to handle selecting the proper |
Brett Cannon | d2e7b33 | 2009-02-17 02:45:03 +0000 | [diff] [blame] | 476 | module object to load with. The decorated method is expected to have a call |
Brett Cannon | 2a922ed | 2009-03-09 03:35:50 +0000 | [diff] [blame] | 477 | signature taking two positional arguments |
| 478 | (e.g. ``load_module(self, module)``) for which the second argument |
Guido van Rossum | 0961354 | 2009-03-30 20:34:57 +0000 | [diff] [blame] | 479 | will be the module **object** to be used by the loader. |
| 480 | Note that the decorator |
Brett Cannon | 57b46f5 | 2009-03-02 14:38:26 +0000 | [diff] [blame] | 481 | will not work on static methods because of the assumption of two |
Brett Cannon | 2a922ed | 2009-03-09 03:35:50 +0000 | [diff] [blame] | 482 | arguments. |
Brett Cannon | d2e7b33 | 2009-02-17 02:45:03 +0000 | [diff] [blame] | 483 | |
Guido van Rossum | 0961354 | 2009-03-30 20:34:57 +0000 | [diff] [blame] | 484 | The decorated method will take in the **name** of the module to be loaded |
| 485 | as expected for a :term:`loader`. If the module is not found in |
Brett Cannon | 57b46f5 | 2009-03-02 14:38:26 +0000 | [diff] [blame] | 486 | :data:`sys.modules` then a new one is constructed with its |
| 487 | :attr:`__name__` attribute set. Otherwise the module found in |
| 488 | :data:`sys.modules` will be passed into the method. If an |
Brett Cannon | d2e7b33 | 2009-02-17 02:45:03 +0000 | [diff] [blame] | 489 | exception is raised by the decorated method and a module was added to |
| 490 | :data:`sys.modules` it will be removed to prevent a partially initialized |
Brett Cannon | 57b46f5 | 2009-03-02 14:38:26 +0000 | [diff] [blame] | 491 | module from being in left in :data:`sys.modules`. If the module was already |
| 492 | in :data:`sys.modules` then it is left alone. |
Brett Cannon | d2e7b33 | 2009-02-17 02:45:03 +0000 | [diff] [blame] | 493 | |
Guido van Rossum | 0961354 | 2009-03-30 20:34:57 +0000 | [diff] [blame] | 494 | Use of this decorator handles all the details of which module object a |
Brett Cannon | 57b46f5 | 2009-03-02 14:38:26 +0000 | [diff] [blame] | 495 | loader should initialize as specified by :pep:`302`. |
| 496 | |
Georg Brandl | 8a1caa2 | 2010-07-29 16:01:11 +0000 | [diff] [blame] | 497 | .. decorator:: set_loader |
Brett Cannon | 2cf03a8 | 2009-03-10 05:17:37 +0000 | [diff] [blame] | 498 | |
Guido van Rossum | 0961354 | 2009-03-30 20:34:57 +0000 | [diff] [blame] | 499 | A :term:`decorator` for a :term:`loader` method, |
| 500 | to set the :attr:`__loader__` |
Brett Cannon | 2cf03a8 | 2009-03-10 05:17:37 +0000 | [diff] [blame] | 501 | attribute on loaded modules. If the attribute is already set the decorator |
| 502 | does nothing. It is assumed that the first positional argument to the |
| 503 | wrapped method is what :attr:`__loader__` should be set to. |
| 504 | |
Georg Brandl | 8a1caa2 | 2010-07-29 16:01:11 +0000 | [diff] [blame] | 505 | .. decorator:: set_package |
Brett Cannon | 57b46f5 | 2009-03-02 14:38:26 +0000 | [diff] [blame] | 506 | |
| 507 | A :term:`decorator` for a :term:`loader` to set the :attr:`__package__` |
| 508 | attribute on the module returned by the loader. If :attr:`__package__` is |
Georg Brandl | 375aec2 | 2011-01-15 17:03:02 +0000 | [diff] [blame] | 509 | set and has a value other than ``None`` it will not be changed. |
Brett Cannon | 57b46f5 | 2009-03-02 14:38:26 +0000 | [diff] [blame] | 510 | Note that the module returned by the loader is what has the attribute |
| 511 | set on and not the module found in :data:`sys.modules`. |
Guido van Rossum | 0961354 | 2009-03-30 20:34:57 +0000 | [diff] [blame] | 512 | |
Brett Cannon | 16248a4 | 2009-04-01 20:47:14 +0000 | [diff] [blame] | 513 | Reliance on this decorator is discouraged when it is possible to set |
| 514 | :attr:`__package__` before the execution of the code is possible. By |
| 515 | setting it before the code for the module is executed it allows the |
| 516 | attribute to be used at the global level of the module during |
| 517 | initialization. |
| 518 | |