Python编程中对MonkeyPatch猴子补丁开发方式

class Foo(object):
 def bar(self):
 print 'Foo.bar'

def bar(self):
 print 'Modified bar'

Foo().bar()

Foo.bar = bar

Foo().bar()

from eventlet import patcher

# *NOTE: there might be some funny business with the "SOCKS" module
# if it even still exists
from eventlet.green import socket

patcher.inject('ftplib', globals(), ('socket', socket))

del patcher

inject函数会将eventlet的socket模块注入标准的ftplib中，globals dict被传入以做适当的修改。

让我们接着来看一下inject的实现。

__exclude = set(('__builtins__', '__file__', '__name__'))

def inject(module_name, new_globals, *additional_modules):
 """Base method for "injecting" greened modules into an imported module. It
 imports the module specified in *module_name*, arranging things so
 that the already-imported modules in *additional_modules* are used when
 *module_name* makes its imports.

 *new_globals* is either None or a globals dictionary that gets populated
 with the contents of the *module_name* module. This is useful when creating
 a "green" version of some other module.

 *additional_modules* should be a collection of two-element tuples, of the
 form (, ). If it's not specified, a default selection of
 name/module pairs is used, which should cover all use cases but may be
 slower because there are inevitably redundant or unnecessary imports.
 """
 if not additional_modules:
 # supply some defaults
 additional_modules = (
 _green_os_modules() +
 _green_select_modules() +
 _green_socket_modules() +
 _green_thread_modules() +
 _green_time_modules())

 ## Put the specified modules in sys.modules for the duration of the import
 saved = {}
 for name, mod in additional_modules:
 saved[name] = sys.modules.get(name, None)
 sys.modules[name] = mod

 ## Remove the old module from sys.modules and reimport it while
 ## the specified modules are in place
 old_module = sys.modules.pop(module_name, None)
 try:
 module = __import__(module_name, {}, {}, module_name.split('.')[:-1])

 if new_globals is not None:
 ## Update the given globals dictionary with everything from this new module
 for name in dir(module):
 if name not in __exclude:
 new_globals[name] = getattr(module, name)

 ## Keep a reference to the new module to prevent it from dying
 sys.modules['__patched_module_' + module_name] = module
 finally:
 ## Put the original module back
 if old_module is not None:
 sys.modules[module_name] = old_module
 elif module_name in sys.modules:
 del sys.modules[module_name]

 ## Put all the saved modules back
 for name, mod in additional_modules:
 if saved[name] is not None:
 sys.modules[name] = saved[name]
 else:
 del sys.modules[name]

 return module

if new_globals is not None:
 ## Update the given globals dictionary with everything from this new module
 for name in dir(module):
 if name not in __exclude:
 new_globals[name] = getattr(module, name)