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

__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)