Source code for nltk.lazyimport

# This module is from mx/DateTime/ and is
# distributed under the terms of the Public License Agreement

""" 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;
    See the documentation for further information on copyrights,
    or contact the author. All Rights Reserved.

### Constants

_debug = 0


[docs]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
[docs] 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 name = self.__lazymodule_name if self.__lazymodule_loaded: return self.__lazymodule_locals[name] if _debug: print("LazyModule: Loading module %r" % name) self.__lazymodule_locals[name] = module = __import__( 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" % 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__