Python binary number - recursion

Question

def question2_a(num_str):  # 1001
    if len(num_str) == 0:
        return True
    if num_str[0] != ("0" or "1"):
        return False
    return question2_a(num_str[1: ])

print(question2_a("100"))

I cant understand, why do I get False?? the numbers are "0" or "1", but I still get False...

same with this code:

def question2_a(num_str):  # 1001
    if len(num_str) == 0:
         return True
    if num_str[0] == ("1" or "0"):
         return question2_a(num_str[1: ])

 print(question2_a("1001010"))

Why do I get None here? it is really annoying, I am doing nothing wrong, but I keep getting None here although there is no problem

And lastly:

def question2_a(num_str):  # 1001
    if len(num_str) == 0:
        return True
     if num_str[0] == ("1" or "0"):
        return question2_a(num_str[1: ])
    else:
         return False

 print(question2_a("1001010"))

Why do I get False here also? I should get True..

Python is not English. `("0" or "1")` returns `"0"`. I'd say `num_str[0] in {"0", "1"}` — Peter Wood, May 20 '22 at 09:55
@PeterWood What do you mean? I am doing indexing, if the index is "0" or "1", then just call the function again... — Analysis_Complex_Study, May 20 '22 at 09:55
You're not reading what @PeterWood is saying: `'0' or '1'` evaluates to `'0'` because the logical operator finds `'0'` 'truthy' and the resulting value of the expression is `'0'`. This is a commonly asked question on StackOverflow (sometimes about 'or', sometimes about 'and') - the bottomline is "that's not how and/or works", you cannot `or` two values together and expect Python to understand what you meant (in English) — Grismar, May 20 '22 at 09:58
@Grismar Then how am I supposed to call "0" or "1" if I cannot do it?... its impossible to call it then lol... — Analysis_Complex_Study, May 20 '22 at 10:03
@PeterWood yea but we are not allowed to use in, that is the problem. — Analysis_Complex_Study, May 20 '22 at 10:11
@PeterWood I tried it before too, but it did not work. It gave me the same problem. — Analysis_Complex_Study, May 20 '22 at 10:15
See how to create a [mcve]. What I've posted should work. If it doesn't work, you're doing something wrong. Try printing the value of `num_str[0]` to validate your understanding. — Peter Wood, May 20 '22 at 10:25
@PeterWood Thanks, I will try it in a bit and update if I managed to do it :) — Analysis_Complex_Study, May 20 '22 at 10:26
@PeterWood https://pastebin.com/UiKgPA9S - See , it is still happening... I did as you said — Analysis_Complex_Study, May 20 '22 at 10:30
https://pastebin.com/RCDpbaQ6 Okay, I think I managed to make it work, but it still doesnt help me.. why did it not work when I did != and it worked when I did ==? @PeterWood — Analysis_Complex_Study, May 20 '22 at 10:42
@TryingToMath think about it. If the value is `"0"` then one of the expressions will be `True`. Same for `"1"`. Probably what you want is `if (num_str[0] != "0") and (num_str[0] != "1"):` — Peter Wood, May 20 '22 at 11:50
@PeterWood ohhh right, I see what you say.. didnt notice.. Thanks. — Analysis_Complex_Study, May 20 '22 at 12:31

Python binary number - recursion

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