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# This module is from mx/DateTime/LazyModule.py and is
# distributed under the terms of the eGenix.com Public License Agreement
# https://www.egenix.com/products/eGenix.com-Public-License-1.1.0.pdf
""" Helper to enable simple lazy module import.
'Lazy' means the actual import is deferred until an attribute is
requested from the module's namespace. This has the advantage of
allowing all imports to be done at the top of a script (in a
prominent and visible place) without having a great impact
on startup time.
Copyright (c) 1999-2005, Marc-Andre Lemburg; mailto:[email protected]
See the documentation for further information on copyrights,
or contact the author. All Rights Reserved.
"""
### Constants
_debug = 0
###
class LazyModule:
"""Lazy module class.
Lazy modules are imported into the given namespaces whenever a
non-special attribute (there are some attributes like __doc__
that class instances handle without calling __getattr__) is
requested. The module is then registered under the given name
in locals usually replacing the import wrapper instance. The
import itself is done using globals as global namespace.
Example of creating a lazy load module:
ISO = LazyModule('ISO',locals(),globals())
Later, requesting an attribute from ISO will load the module
automatically into the locals() namespace, overriding the
LazyModule instance:
t = ISO.Week(1998,1,1)
"""
# Flag which indicates whether the LazyModule is initialized or not
__lazymodule_init = 0
# Name of the module to load
__lazymodule_name = ""
# Flag which indicates whether the module was loaded or not
__lazymodule_loaded = 0
# Locals dictionary where to register the module
__lazymodule_locals = None
# Globals dictionary to use for the module import
__lazymodule_globals = None
def __init__(self, name, locals, globals=None):
"""Create a LazyModule instance wrapping module name.
The module will later on be registered in locals under the
given module name.
globals is optional and defaults to locals.
"""
self.__lazymodule_locals = locals
if globals is None:
globals = locals
self.__lazymodule_globals = globals
mainname = globals.get("__name__", "")
if mainname:
self.__name__ = mainname + "." + name
self.__lazymodule_name = name
else:
self.__name__ = self.__lazymodule_name = name
self.__lazymodule_init = 1
def __lazymodule_import(self):
"""Import the module now."""
# Load and register module
local_name = self.__lazymodule_name # e.g. "toolbox"
full_name = self.__name__ # e.g. "nltk.toolbox"
if self.__lazymodule_loaded:
return self.__lazymodule_locals[local_name]
if _debug:
print("LazyModule: Loading module %r" % full_name)
self.__lazymodule_locals[local_name] = module = __import__(
full_name, self.__lazymodule_locals, self.__lazymodule_globals, "*"
)
# Fill namespace with all symbols from original module to
# provide faster access.
self.__dict__.update(module.__dict__)
# Set import flag
self.__dict__["__lazymodule_loaded"] = 1
if _debug:
print("LazyModule: Module %r loaded" % full_name)
return module
def __getattr__(self, name):
"""Import the module on demand and get the attribute."""
if self.__lazymodule_loaded:
raise AttributeError(name)
if _debug:
print(
"LazyModule: "
"Module load triggered by attribute %r read access" % name
)
module = self.__lazymodule_import()
return getattr(module, name)
def __setattr__(self, name, value):
"""Import the module on demand and set the attribute."""
if not self.__lazymodule_init:
self.__dict__[name] = value
return
if self.__lazymodule_loaded:
self.__lazymodule_locals[self.__lazymodule_name] = value
self.__dict__[name] = value
return
if _debug:
print(
"LazyModule: "
"Module load triggered by attribute %r write access" % name
)
module = self.__lazymodule_import()
setattr(module, name, value)
def __repr__(self):
return "<LazyModule '%s'>" % self.__name__
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