/usr/share/pyshared/mx/DateTime/LazyModule.py is in python-egenix-mxdatetime 3.2.1-1ubuntu1.
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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 | """ 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:mal@lemburg.com
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 inidicates 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
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__
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