How to do switch case in python depending on 4 variables

Question

I am trying to select one of the 16 dictionaries that I have created, based on the value of 4 input variables.

I think it could be done with switch but so far I have not been able to get it.

I think the "logic" could be something similar to this:

variable_1 = 0
variable_2 = 1
variable_3 = 1
variable_4 = 0



def func_select_dict(variable_1, variable_2, variable_3, variable_4)

        switch(0,0,0,0):
                final_dictionary = dictionary_1

        switch(0,0,0,1):
                final_dictionary = dictionary_2

        switch(0,0,1,0):
                final_dictionary = dictionary_3

        ...............

        switch(1,1,1,1):
                final_dictionary = dictionary_16

Any idea?

Python doesn't have a switch case statement, so you might need to rethink. — khelwood, Sep 17 '20 at 17:32
Does this answer your question? [Why doesn't Python have switch-case?](https://stackoverflow.com/questions/46701063/why-doesnt-python-have-switch-case) — Sencer H., Sep 17 '20 at 18:22

score 0 · Answer 1 · answered Sep 17 '20 at 17:34

If you put your dictionaries in a list, for example

>>> dicts = [{'dict': i} for i in range(16)]
>>> dicts
[{'dict': 0}, {'dict': 1}, {'dict': 2}, {'dict': 3}, {'dict': 4}, {'dict': 5}, {'dict': 6}, {'dict': 7}, {'dict': 8}, {'dict': 9}, {'dict': 10}, {'dict': 11}, {'dict': 12}, {'dict': 13}, {'dict': 14}, {'dict': 15}]

You can use some clever bit-shifting to index into that list based on your variables

def to_index(v1, v2, v3, v4):
    return v1 << 3 | v2 << 2 | v3 << 1 | v4

For example

>>> to_index(0, 1, 1, 0)
6
>>> dicts[to_index(0, 1, 1, 0)]
{'dict': 6}

Your current approach will not work because Python does not have switch statements, and even if it did canonically that only works with integral types, not tuples.

Thanks, that's just what I needed! – Inakima Sep 18 '20 at 07:04 — Inakima, Sep 18 '20 at 07:04

How to do switch case in python depending on 4 variables

1 Answers1