如何在 Python 函数中将参数绑定到给定值？

我有许多函数，它们结合了位置参数和关键字参数，我想将它们的一个参数绑定到一个给定的值(只有在函数定义之后才知道)。有什么通用的方法吗？

我的第一次尝试是:

def f(a,b,c): print a,b,c


def _bind(f, a): return lambda b,c: f(a,b,c)


bound_f = bind(f, 1)

但是，为此我需要知道传递给 f的确切参数，而且不能使用单个函数来绑定我感兴趣的所有函数(因为它们有不同的参数列表)。

python

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小开

You probably want the partial function from functools.

小开

最佳答案

>>> from functools import partial
>>> def f(a, b, c):
...   print a, b, c
...
>>> bound_f = partial(f, 1)
>>> bound_f(2, 3)
1 2 3

小开

As suggested by MattH's answer, functools.partial is the way to go.

However, your question can be read as "how can I implement partial". What your code is missing is the use of ABC1, **kwargs- 2 such uses, actually:

def partial(f, *args, **kwargs):
def wrapped(*args2, **kwargs2):
return f(*args, *args2, **kwargs, **kwargs2)
return wrapped

小开

You can use partial and update_wrapper to bind arguments to given values and preserve __name__ and __doc__ of the original function:

from functools import partial, update_wrapper




def f(a, b, c):
print(a, b, c)




bound_f = update_wrapper(partial(f, 1000), f)


# This will print 'f'
print(bound_f.__name__)


# This will print 1000, 4, 5
bound_f(4, 5)