[Tutor] Regex not working as desired

[Peter Otten]

Alan Gauld via Tutor wrote:

> On 27/02/18 05:13, Cameron Simpson wrote:
> 
>> hard to debug when you do. That's not to say you shouldn't use them, but
>> many people use them for far too much.
> 
> 
>> Finally, you could also consider not using a regexp for this particular
>> task. Python's "int" class can be called with a string, and will raise an
>> exception
> 
> And, as another alternative, you can use all() with a
> generator expression:
> 
>>>> all(c.isdigit() for c in '1234')
> True
>>>> all(c.isdigit() for c in '12c4')
> False
>>>>
> 
> Or generally:
> 
> def all_digits(s):
>     return all(c.isdigit() for c in s)
 
Note that isdigit() already checks all characters in the string:

>>> "123".isdigit()
True
>>> "1a1".isdigit()
False

The only difference to your suggestion is how it handles the empty string:

>>> def all_digits(s):
...     return all(c.isdigit() for c in s)
... 
>>> all_digits("")
True
>>> "".isdigit()
False

A potential problem of str.isdigit() -- and int() -- may be its unicode 
awareness:

>>> s = "\N{CHAM DIGIT ONE}\N{CHAM DIGIT TWO}\N{CHAM DIGIT THREE}"
>>> s
'꩑꩒꩓'
>>> s.isdigit()
True
>>> int(s)
123