mirror of https://github.com/python/cpython
249 lines
7.6 KiB
Python
249 lines
7.6 KiB
Python
#
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# importers.py
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#
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# Demonstration subclasses of imputil.Importer
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#
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# There should be consideration for the imports below if it is desirable
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# to have "all" modules be imported through the imputil system.
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# these are C extensions
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import sys
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import imp
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import struct
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import marshal
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# these are .py modules
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import imputil
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import os
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######################################################################
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_TupleType = type(())
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_StringType = type('')
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######################################################################
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# byte-compiled file suffic character
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_suffix_char = __debug__ and 'c' or 'o'
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# byte-compiled file suffix
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_suffix = '.py' + _suffix_char
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# the C_EXTENSION suffixes
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_c_suffixes = [x for x in imp.get_suffixes() if x[2] == imp.C_EXTENSION]
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def _timestamp(pathname):
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"Return the file modification time as a Long."
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try:
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s = os.stat(pathname)
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except OSError:
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return None
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return int(s[8])
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def _fs_import(dir, modname, fqname):
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"Fetch a module from the filesystem."
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pathname = os.path.join(dir, modname)
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if os.path.isdir(pathname):
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values = { '__pkgdir__' : pathname, '__path__' : [ pathname ] }
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ispkg = 1
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pathname = os.path.join(pathname, '__init__')
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else:
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values = { }
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ispkg = 0
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# look for dynload modules
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for desc in _c_suffixes:
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file = pathname + desc[0]
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try:
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fp = open(file, desc[1])
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except IOError:
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pass
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else:
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module = imp.load_module(fqname, fp, file, desc)
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values['__file__'] = file
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return 0, module, values
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t_py = _timestamp(pathname + '.py')
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t_pyc = _timestamp(pathname + _suffix)
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if t_py is None and t_pyc is None:
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return None
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code = None
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if t_py is None or (t_pyc is not None and t_pyc >= t_py):
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file = pathname + _suffix
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f = open(file, 'rb')
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if f.read(4) == imp.get_magic():
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t = struct.unpack('<I', f.read(4))[0]
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if t == t_py:
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code = marshal.load(f)
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f.close()
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if code is None:
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file = pathname + '.py'
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code = _compile(file, t_py)
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values['__file__'] = file
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return ispkg, code, values
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######################################################################
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#
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# Simple function-based importer
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#
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class FuncImporter(imputil.Importer):
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"Importer subclass to delegate to a function rather than method overrides."
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def __init__(self, func):
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self.func = func
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def get_code(self, parent, modname, fqname):
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return self.func(parent, modname, fqname)
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def install_with(func):
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FuncImporter(func).install()
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######################################################################
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#
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# Base class for archive-based importing
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#
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class PackageArchiveImporter(imputil.Importer):
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"""Importer subclass to import from (file) archives.
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This Importer handles imports of the style <archive>.<subfile>, where
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<archive> can be located using a subclass-specific mechanism and the
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<subfile> is found in the archive using a subclass-specific mechanism.
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This class defines two hooks for subclasses: one to locate an archive
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(and possibly return some context for future subfile lookups), and one
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to locate subfiles.
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"""
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def get_code(self, parent, modname, fqname):
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if parent:
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# the Importer._finish_import logic ensures that we handle imports
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# under the top level module (package / archive).
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assert parent.__importer__ == self
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# if a parent "package" is provided, then we are importing a
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# sub-file from the archive.
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result = self.get_subfile(parent.__archive__, modname)
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if result is None:
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return None
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if isinstance(result, _TupleType):
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assert len(result) == 2
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return (0,) + result
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return 0, result, {}
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# no parent was provided, so the archive should exist somewhere on the
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# default "path".
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archive = self.get_archive(modname)
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if archive is None:
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return None
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return 1, "", {'__archive__':archive}
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def get_archive(self, modname):
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"""Get an archive of modules.
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This method should locate an archive and return a value which can be
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used by get_subfile to load modules from it. The value may be a simple
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pathname, an open file, or a complex object that caches information
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for future imports.
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Return None if the archive was not found.
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"""
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raise RuntimeError("get_archive not implemented")
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def get_subfile(self, archive, modname):
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"""Get code from a subfile in the specified archive.
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Given the specified archive (as returned by get_archive()), locate
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and return a code object for the specified module name.
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A 2-tuple may be returned, consisting of a code object and a dict
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of name/values to place into the target module.
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Return None if the subfile was not found.
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"""
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raise RuntimeError("get_subfile not implemented")
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class PackageArchive(PackageArchiveImporter):
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"PackageArchiveImporter subclass that refers to a specific archive."
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def __init__(self, modname, archive_pathname):
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self.__modname = modname
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self.__path = archive_pathname
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def get_archive(self, modname):
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if modname == self.__modname:
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return self.__path
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return None
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# get_subfile is passed the full pathname of the archive
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######################################################################
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#
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# Emulate the standard directory-based import mechanism
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#
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class DirectoryImporter(imputil.Importer):
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"Importer subclass to emulate the standard importer."
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def __init__(self, dir):
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self.dir = dir
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def get_code(self, parent, modname, fqname):
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if parent:
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dir = parent.__pkgdir__
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else:
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dir = self.dir
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# Return the module (and other info) if found in the specified
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# directory. Otherwise, return None.
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return _fs_import(dir, modname, fqname)
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def __repr__(self):
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return '<%s.%s for "%s" at 0x%x>' % (self.__class__.__module__,
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self.__class__.__name__,
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self.dir,
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id(self))
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######################################################################
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#
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# Emulate the standard path-style import mechanism
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#
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class PathImporter(imputil.Importer):
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def __init__(self, path=sys.path):
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self.path = path
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def get_code(self, parent, modname, fqname):
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if parent:
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# we are looking for a module inside of a specific package
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return _fs_import(parent.__pkgdir__, modname, fqname)
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# scan sys.path, looking for the requested module
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for dir in self.path:
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if isinstance(dir, _StringType):
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result = _fs_import(dir, modname, fqname)
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if result:
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return result
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# not found
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return None
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######################################################################
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def _test_dir():
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"Debug/test function to create DirectoryImporters from sys.path."
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imputil.ImportManager().install()
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path = sys.path[:]
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path.reverse()
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for d in path:
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sys.path.insert(0, DirectoryImporter(d))
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sys.path.insert(0, imputil.BuiltinImporter())
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def _test_revamp():
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"Debug/test function for the revamped import system."
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imputil.ImportManager().install()
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sys.path.insert(0, PathImporter())
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sys.path.insert(0, imputil.BuiltinImporter())
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