Pass list to function by value

Question

I want to pass a list into function by value. By default, lists and other complex objects passed to function by reference. Here is some desision:

def add_at_         


        

Answer 1

This might be an interesting use case for a decorator function. Something like this:

def pass_by_value(f):
    def _f(*args, **kwargs):
        args_copied = copy.deepcopy(args)
        kwargs_copied = copy.deepcopy(kwargs)
        return f(*args_copied, **kwargs_copied)
    return _f

pass_by_value takes a function f as input and creates a new function _f that deep-copies all its parameters and then passes them to the original function f.

Usage:

@pass_by_value
def add_at_rank(ad, rank):
    ad.append(4)
    rank[3] = "bar"
    print "inside function", ad, rank

a, r = [1,2,3], {1: "foo"}
add_at_rank(a, r)
print "outside function", a, r

Output:

"inside function [1, 2, 3, 4] {1: 'foo', 3: 'bar'}"
"outside function [1, 2, 3] {1: 'foo'}"