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369 lines
11 KiB
Python
369 lines
11 KiB
Python
"""Import hook support.
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Consistent use of this module will make it possible to change the
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different mechanisms involved in loading modules independently.
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While the built-in module imp exports interfaces to the built-in
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module searching and loading algorithm, and it is possible to replace
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the built-in function __import__ in order to change the semantics of
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the import statement, until now it has been difficult to combine the
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effect of different __import__ hacks, like loading modules from URLs
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(rimport.py), implementing a hierarchical module namespace (newimp.py)
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or restricted execution (rexec.py).
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This module defines three new concepts:
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(1) A "file system hooks" class provides an interface to a filesystem.
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One hooks class is defined (Hooks), which uses the interface provided
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by standard modules os and os.path. It should be used as the base
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class for other hooks classes.
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(2) A "module loader" class provides an interface to to search for a
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module in a search path and to load it. It defines a method which
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searches for a module in a single directory; by overriding this method
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one can redefine the details of the search. If the directory is None,
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built-in and frozen modules are searched instead.
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Two module loader class are defined, both implementing the search
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strategy used by the built-in __import__ function: ModuleLoader uses
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the imp module's find_module interface, while HookableModuleLoader
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uses a file system hooks class to interact with the file system. Both
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use the imp module's load_* interfaces to actually load the module.
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(3) A "module importer" class provides an interface to import a
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module, as well as interfaces to reload and unload a module. It also
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provides interfaces to install and uninstall itself instead of the
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default __import__ and reload (and unload) functions.
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One module importer class is defined (ModuleImporter), which uses a
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module loader instance passed in (by default HookableModuleLoader is
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instantiated).
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The classes defined here should be used as base classes for extended
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functionality along those lines.
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If a module mporter class supports dotted names, its import_module()
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must return a different value depending on whether it is called on
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behalf of a "from ... import ..." statement or not. (This is caused
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by the way the __import__ hook is used by the Python interpreter.) It
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would also do wise to install a different version of reload().
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XXX Should the imp.load_* functions also be called via the hooks
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instance?
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"""
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import __builtin__
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import imp
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import os
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import sys
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from imp import C_EXTENSION, PY_SOURCE, PY_COMPILED
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BUILTIN_MODULE = 32
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FROZEN_MODULE = 33
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class _Verbose:
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def __init__(self, verbose = 0):
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self.verbose = verbose
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def get_verbose(self):
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return self.verbose
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def set_verbose(self, verbose):
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self.verbose = verbose
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# XXX The following is an experimental interface
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def note(self, *args):
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if self.verbose:
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apply(self.message, args)
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def message(self, format, *args):
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print format%args
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class BasicModuleLoader(_Verbose):
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"""Basic module loader.
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This provides the same functionality as built-in import. It
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doesn't deal with checking sys.modules -- all it provides is
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find_module() and a load_module(), as well as find_module_in_dir()
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which searches just one directory, and can be overridden by a
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derived class to change the module search algorithm when the basic
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dependency on sys.path is unchanged.
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The interface is a little more convenient than imp's:
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find_module(name, [path]) returns None or 'stuff', and
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load_module(name, stuff) loads the module.
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"""
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def find_module(self, name, path = None):
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if path is None:
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path = [None] + self.default_path()
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for dir in path:
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stuff = self.find_module_in_dir(name, dir)
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if stuff: return stuff
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return None
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def default_path(self):
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return sys.path
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def find_module_in_dir(self, name, dir):
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if dir is None:
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return self.find_builtin_module(name)
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else:
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try:
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return imp.find_module(name, [dir])
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except ImportError:
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return None
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def find_builtin_module(self, name):
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if imp.is_builtin(name):
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return None, '', ('', '', BUILTIN_MODULE)
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if imp.is_frozen(name):
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return None, '', ('', '', FROZEN_MODULE)
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return None
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def load_module(self, name, stuff):
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file, filename, (suff, mode, type) = stuff
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try:
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if type == BUILTIN_MODULE:
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return imp.init_builtin(name)
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if type == FROZEN_MODULE:
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return imp.init_frozen(name)
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if type == C_EXTENSION:
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return imp.load_dynamic(name, filename, file)
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if type == PY_SOURCE:
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return imp.load_source(name, filename, file)
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if type == PY_COMPILED:
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return imp.load_compiled(name, filename, file)
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finally:
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if file: file.close()
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raise ImportError, "Unrecognized module type (%s) for %s" % \
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(`type`, name)
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class Hooks(_Verbose):
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"""Hooks into the filesystem and interpreter.
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By deriving a subclass you can redefine your filesystem interface,
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e.g. to merge it with the URL space.
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This base class behaves just like the native filesystem.
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"""
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# imp interface
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def get_suffixes(self): return imp.get_suffixes()
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def new_module(self, name): return imp.new_module(name)
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def is_builtin(self, name): return imp.is_builtin(name)
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def init_builtin(self, name): return imp.init_builtin(name)
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def is_frozen(self, name): return imp.is_frozen(name)
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def init_frozen(self, name): return imp.init_frozen(name)
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def get_frozen_object(self, name): return imp.get_frozen_object(name)
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def load_source(self, name, filename, file=None):
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return imp.load_source(name, filename, file)
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def load_compiled(self, name, filename, file=None):
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return imp.load_compiled(name, filename, file)
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def load_dynamic(self, name, filename, file=None):
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return imp.load_dynamic(name, filename, file)
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def add_module(self, name):
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d = self.modules_dict()
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if d.has_key(name): return d[name]
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d[name] = m = self.new_module(name)
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return m
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# sys interface
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def modules_dict(self): return sys.modules
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def default_path(self): return sys.path
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def path_split(self, x): return os.path.split(x)
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def path_join(self, x, y): return os.path.join(x, y)
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def path_isabs(self, x): return os.path.isabs(x)
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# etc.
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def path_exists(self, x): return os.path.exists(x)
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def path_isdir(self, x): return os.path.isdir(x)
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def path_isfile(self, x): return os.path.isfile(x)
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def path_islink(self, x): return os.path.islink(x)
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# etc.
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def openfile(self, *x): return apply(open, x)
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openfile_error = IOError
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def listdir(self, x): return os.listdir(x)
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listdir_error = os.error
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# etc.
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class ModuleLoader(BasicModuleLoader):
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"""Default module loader; uses file system hooks.
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By defining suitable hooks, you might be able to load modules from
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other sources than the file system, e.g. from compressed or
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encrypted files, tar files or (if you're brave!) URLs.
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"""
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def __init__(self, hooks = None, verbose = 0):
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BasicModuleLoader.__init__(self, verbose)
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self.hooks = hooks or Hooks(verbose)
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def default_path(self):
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return self.hooks.default_path()
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def modules_dict(self):
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return self.hooks.modules_dict()
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def get_hooks(self):
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return self.hooks
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def set_hooks(self, hooks):
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self.hooks = hooks
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def find_builtin_module(self, name):
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if self.hooks.is_builtin(name):
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return None, '', ('', '', BUILTIN_MODULE)
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if self.hooks.is_frozen(name):
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return None, '', ('', '', FROZEN_MODULE)
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return None
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def find_module_in_dir(self, name, dir):
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if dir is None:
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return self.find_builtin_module(name)
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for info in self.hooks.get_suffixes():
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suff, mode, type = info
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fullname = self.hooks.path_join(dir, name+suff)
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try:
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fp = self.hooks.openfile(fullname, mode)
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return fp, fullname, info
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except self.hooks.openfile_error:
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pass
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return None
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def load_module(self, name, stuff):
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file, filename, (suff, mode, type) = stuff
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if type == BUILTIN_MODULE:
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return self.hooks.init_builtin(name)
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if type == FROZEN_MODULE:
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return self.hooks.init_frozen(name)
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if type == C_EXTENSION:
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m = self.hooks.load_dynamic(name, filename, file)
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elif type == PY_SOURCE:
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m = self.hooks.load_source(name, filename, file)
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elif type == PY_COMPILED:
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m = self.hooks.load_compiled(name, filename, file)
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else:
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raise ImportError, "Unrecognized module type (%s) for %s" % \
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(`type`, name)
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m.__file__ = filename
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return m
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class FancyModuleLoader(ModuleLoader):
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"""Fancy module loader -- parses and execs the code itself."""
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def load_module(self, name, stuff):
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file, filename, (suff, mode, type) = stuff
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if type == FROZEN_MODULE:
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code = self.hooks.get_frozen_object(name)
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elif type == PY_COMPILED:
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import marshal
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file.seek(8)
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code = marshal.load(file)
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elif type == PY_SOURCE:
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data = file.read()
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code = compile(data, filename, 'exec')
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else:
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return ModuleLoader.load_module(self, name, stuff)
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m = self.hooks.add_module(name)
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m.__file__ = filename
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exec code in m.__dict__
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return m
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class ModuleImporter(_Verbose):
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"""Default module importer; uses module loader.
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This provides the same functionality as built-in import, when
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combined with ModuleLoader.
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"""
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def __init__(self, loader = None, verbose = 0):
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_Verbose.__init__(self, verbose)
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self.loader = loader or ModuleLoader(None, verbose)
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self.modules = self.loader.modules_dict()
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def get_loader(self):
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return self.loader
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def set_loader(self, loader):
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self.loader = loader
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def get_hooks(self):
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return self.loader.get_hooks()
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def set_hooks(self, hooks):
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return self.loader.set_hooks(hooks)
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def import_module(self, name, globals={}, locals={}, fromlist=[]):
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if self.modules.has_key(name):
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return self.modules[name] # Fast path
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stuff = self.loader.find_module(name)
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if not stuff:
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raise ImportError, "No module named %s" % name
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return self.loader.load_module(name, stuff)
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def reload(self, module, path = None):
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name = module.__name__
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stuff = self.loader.find_module(name, path)
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if not stuff:
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raise ImportError, "Module %s not found for reload" % name
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return self.loader.load_module(name, stuff)
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def unload(self, module):
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del self.modules[module.__name__]
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# XXX Should this try to clear the module's namespace?
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def install(self):
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self.save_import_module = __builtin__.__import__
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self.save_reload = __builtin__.reload
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if not hasattr(__builtin__, 'unload'):
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__builtin__.unload = None
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self.save_unload = __builtin__.unload
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__builtin__.__import__ = self.import_module
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__builtin__.reload = self.reload
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__builtin__.unload = self.unload
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def uninstall(self):
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__builtin__.__import__ = self.save_import_module
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__builtin__.reload = self.save_reload
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__builtin__.unload = self.save_unload
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if not __builtin__.unload:
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del __builtin__.unload
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default_importer = None
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current_importer = None
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def install(importer = None):
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global current_importer
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current_importer = importer or default_importer or ModuleImporter()
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current_importer.install()
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def uninstall():
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global current_importer
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current_importer.uninstall()
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