传递/更改一个函数的参数，该参数作为另一个函数的参数传递

Question

I have one weird problem. I want to pass/change an argument of a function which itself is passed as an argument in some other function. See the below code for more details

def generic_method(selector_type='CSS', selector=None, parent_element=None, postfunc=None):

    # Do your stuff and get value of attr_value
    print "Doing Stuff"
    attr_value = '$123.70'

    print "Post-Processing Step"
    if postfunc:
        attr_value = postfunc(attrval=attr_value)

    return attr_value

# The 2 methods below are in separate file 
from functools import partial
def method_in_bot():
    p, q, r = 11, 12, 13
    postfunc = partial(post_processing, 12, p, q, r, post=23)
    value = generic_method('XPATH', '.class-name', 'parent_element', postfunc)
    return value

def post_processing(y=None, *args, **kwargs):
    attr_value = kwargs.get('attrval', 'None')
    if attr_value:
        return attr_value.split('$')
    return []

So I passed my post_processing method along with all its parameters to my generic_method by using functools's partial and also passed a new variable attrval to my post_processing method. But what is more desirable is to pass or assign attr_value directly to variable y to post_processing .

I was looking for ways to modify functions parameters during run-time. I was searching over the net and found out that their is a inspect library in python which tells you about the arguments passed to the function. Can it be used in this case.

Answer 1

In Python 3, you could do def post_processing(*args, y=None, **kwargs): and that would be it. With Python 2 you have to find a different technique than partial . Or maybe subclass it as in implementing functools.partial that prepends additional arguments .