How to make a function do reverse of its job Python

Question

How do you make a function do reverse of what it was programmed to do in Python without reprogramming the entire function? For example:

swap1 = "abc"
swap2 = "def"
def swap():
    global swap1, swap2
    swap1 = swap2

into

swap1 = "abc"
swap2 = "def"
def swap():
    global swap1, swap2
    swap2 = swap1

Any help is appreciated.

Sprinkle pixie dust on it and wave your magic wand. – Ignacio Vazquez-Abrams Aug 12 '14 at 00:12 — Ignacio Vazquez-Abrams, Aug 12 '14 at 00:12
"Vote down if needed"? Is this a troll question? – Beginner Aug 12 '14 at 00:18 — Beginner, Aug 12 '14 at 00:18

score 5 · Answer 1 · edited May 23 '17 at 10:26

A function can only do what it's designed to do. While some functions, by design, are reversible, there is no way to create a general case reverse function. Furthermore, many functions (notably hash functions) are intentionally designed to not be reversible, either simply because information is lost along the way, or because it is intentionally computationally impossible to reverse.

You would do better to rethink your design here - the pattern you demonstrated above using globals is highly undesirable, it will lead to very complex, difficult to maintain or understand code.

score 3 · Answer 2 · answered Aug 12 '14 at 00:16

3

in general there is no such way to do this. the computer cannot know what you mean by "reverse", since there are different ways of the "reverse of a function".

answered Aug 12 '14 at 00:16

supinf

302
4
13

score 2 · Accepted Answer · answered Aug 12 '14 at 01:21

2

No way to 'reverse' a function. Only rewriting it is possible. Sorry.

answered Aug 12 '14 at 01:21

user3576467

424
1
7
10

How to make a function do reverse of its job Python

3 Answers3