翻译自：https://pymotw.com/3/functools/index.html

functools模块提供了调整和扩展函数以及其他 callable objects的工具方法。

装饰器（Decorators）

1）partial函数
partial函数可用来修改函数的默认参数值，增加额外的位置参数（positional arguments）或名称参数（ named arguments），你不需再重新定义函数，只需像使用原函数一样的使用partial包裹后的函数。

import functools


def myfunc(a, b=2):
    "Docstring for myfunc()."
    print('  called myfunc with:', (a, b))


def show_details(name, f, is_partial=False):
    "Show details of a callable object."
    print('{}:'.format(name))
    print('  object:', f)
    if not is_partial:
        print('  __name__:', f.__name__)
    if is_partial:
        print('  func:', f.func)
        print('  args:', f.args)
        print('  keywords:', f.keywords)
    return


show_details('myfunc', myfunc)
myfunc('a', 3)
print()

# Set a different default value for 'b', but require
# the caller to provide 'a'.
p1 = functools.partial(myfunc, b=4)
show_details('partial with named default', p1, True)
p1('passing a')
p1('override b', b=5)
print()

# Set default values for both 'a' and 'b'.
p2 = functools.partial(myfunc, 'default a', b=99)
show_details('partial with defaults', p2, True)
p2()
p2(b='override b')
print()

print('Insufficient arguments:')
p1()

#结果

myfunc:
  object: <function myfunc at 0x1007a6a60>
  __name__: myfunc
  called myfunc with: ('a', 3)

partial with named default:
  object: functools.partial(<function myfunc at 0x1007a6a60>,
b=4)
  func: <function myfunc at 0x1007a6a60>
  args: ()
  keywords: {
  'b': 4}
  called myfunc with: ('passing a', 4)
  called myfunc with: ('override b', 5)

partial with defaults:
  object: functools.partial(<function myfunc at 0x1007a6a60>,
'default a', b=99)
  func: <function myfunc at 0x1007a6a60>
  args: ('default a',)
  keywords: {
  'b': 99}
  called myfunc with: ('default a', 99)
  called myfunc with: ('default a', 'override b')

Insufficient arguments:
Traceback (most recent call last):
  File "functools_partial.py", line 51, in <module>
    p1()
TypeError: myfunc() missing 1 required positional argument: 'a'

partial不仅可用于函数，其他的 callable object也可以也可以使用。

import functools


class MyClass:
    "Demonstration class for functools"

    def __call__(self, e, f=6):
        "Docstring for MyClass.__call__"
        print('  called object with:', (self, e, f))


def show_details(name, f):
    "Show details of a callable object."
    print('{}:'.format(name))
    print(