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Import hook support.
Consistent use of this module will make it possible to change the different mechanisms involved in loading modules independently.
While the built-in module imp exports interfaces to the built-in module searching and loading algorithm, and it is possible to replace the built-in function __import__ in order to change the semantics of the import statement, until now it has been difficult to combine the effect of different __import__ hacks, like loading modules from URLs by rimport.py, or restricted execution by rexec.py.
This module defines three new concepts:
1) A "file system hooks" class provides an interface to a filesystem.
One hooks class is defined (Hooks), which uses the interface provided by standard modules os and os.path. It should be used as the base class for other hooks classes.
2) A "module loader" class provides an interface to search for a module in a search path and to load it. It defines a method which searches for a module in a single directory; by overriding this method one can redefine the details of the search. If the directory is None, built-in and frozen modules are searched instead.
Two module loader class are defined, both implementing the search strategy used by the built-in __import__ function: ModuleLoader uses the imp module's find_module interface, while HookableModuleLoader uses a file system hooks class to interact with the file system. Both use the imp module's load_* interfaces to actually load the module.
3) A "module importer" class provides an interface to import a module, as well as interfaces to reload and unload a module. It also provides interfaces to install and uninstall itself instead of the default __import__ and reload (and unload) functions.
One module importer class is defined (ModuleImporter), which uses a module loader instance passed in (by default HookableModuleLoader is instantiated).
The classes defined here should be used as base classes for extended functionality along those lines.
If a module importer class supports dotted names, its import_module() must return a different value depending on whether it is called on behalf of a "from ... import ..." statement or not. (This is caused by the way the __import__ hook is used by the Python interpreter.) It would also do wise to install a different version of reload().
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BasicModuleLoader Basic module loader. |
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Hooks Hooks into the filesystem and interpreter. |
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ModuleLoader Default module loader; uses file system hooks. |
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FancyModuleLoader Fancy module loader -- parses and execs the code itself. |
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BasicModuleImporter Basic module importer; uses module loader. |
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ModuleImporter A module importer that supports packages. |
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VERBOSE = 0
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BUILTIN_MODULE = 6
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FROZEN_MODULE = 7
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default_importer = None
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current_importer = None
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Imports: __builtin__, imp, os, sys, C_EXTENSION, PY_SOURCE, PY_COMPILED, C_BUILTIN, PY_FROZEN, PKG_DIRECTORY
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