Shorter way to check if a string is not isdigit()

Question

For the sake of learning, is there a shorter way to do: if string.isdigit() == False :

I tried: if !string.isdigit() : and if !(string.isdigit()) : which both didn't work.

@MarounMaroun: because this is so basic that I don't need rep from it. — Fred Foo, May 02 '13 at 10:32
@larsmans: hence the comment at the start of my post: for the sake of learning. I expected it to be something like this. Thanks anyway. — Nick Rutten, May 03 '13 at 01:27

score 20 · Accepted Answer · edited May 02 '13 at 10:42

20

Python's "not" operand is not, not !.

Python's "logical not" operand is not, not !.

edited May 02 '13 at 10:42

jamylak

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answered May 02 '13 at 10:33

Meoiswa

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But it's `not` my fault! In all seriousness, that's why I used the quotes, code notation and normal form to differentiate – Meoiswa May 02 '13 at 10:37

score 15 · Answer 2 · edited May 08 '13 at 21:59

15

In python, you use the not keyword instead of !:

if not string.isdigit():
    do_stuff()

This is equivalent to:

if not False:
    do_stuff()

i.e:

if True:
    do_stuff()

Also, from the PEP 8 Style Guide:

Don't compare boolean values to True or False using ==.

Yes: if greeting:

No: if greeting == True

Worse: if greeting is True:

edited May 08 '13 at 21:59

Stephen

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answered May 02 '13 at 10:32

TerryA

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(Off-topic: Anyone else thinks that `is True` is not *worse* than `== True`, but rather the other way around?) – poke May 02 '13 at 10:45
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@poke http://stackoverflow.com/questions/4591125/is-it-safe-to-replace-with-is-to-compare-boolean-values – TerryA May 02 '13 at 10:46

score 7 · Answer 3 · answered May 02 '13 at 10:31

7

if not my_str.isdigit()

Also, don't use string as a variable name as it is also the name of a widely used standard module.

answered May 02 '13 at 10:31

Volatility

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msklc · Answer 4 · 2020-05-02T17:58:27.703

5

maybe using .isalpha() is an easier way...

so; instead of if not my_str.isdigit() you can try if my_str.isalpha()

it is the shorter way to check if a string is not digit

edited May 02 '20 at 17:58

answered May 02 '20 at 11:59

msklc

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score 0 · Answer 5 · answered Feb 06 '18 at 11:27

0

string.isdigit(g) returns False if g is negative or float. I prefer using following function:

def is_digit(g):
    try:
        float(g)
    except ValueError:
        return False
    return True

answered Feb 06 '18 at 11:27

Anton

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Eric Evans · Answer 6 · 2023-06-14T12:28:16.927

The (!) only works when saying something does not equal something else (!=).

if str.isdigit() != True:

It doesn't make much sense to do it that way because you can just say equals True.

if str.isdigit() == False:

You could also just use not instead of (!).

if not str.isdigit():

Note: this will only work if the string is an integer, it will return false even if it is an integer written as a float (i.e. '1.0'). To check if a string is a number of any kind try this function...

def is_digit(str):     
   try:
      float(str)
   except ValueError:
      return False
   return True

Shorter way to check if a string is not isdigit()

6 Answers6