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creating a function like isdigit() in python

stackoverflow.com › questions › 33467909 › creating-a-function-like-isdigit-in-python

You would need to remove the numbers from the list as you are comparing each character to all the digits at once i.e "1" == "0123456789" , you also need to check every char before returning True:

def is_dig(s):
    numbers = "0123456789"  # single iterable of the numbers
    for i in s:
        if i not in numbers:
            return False
    return bool(s) # return outside the loop also catching empty string

A more efficient approach would be to use the ord and all:

def is_dig(s):
    return len(s) > 0 and all(48 <= ord(ch) <= 57 for ch in s)

The ord of "0" is 48 and the ord of "9" is 57 so if the ord of the char falls in that range then you have a digit, if not all will short circuit and return False.

Using the ord without all and following your own logic would look something like:

def is_dig(s):
    if not s: # empty string
        return False
    for ch in s:
        if not 48 <= ord(ch) <= 57:
            return False
    return True

Answer from Padraic Cunningham on Stack Overflow

W3Schools

w3schools.com › Python › ref_string_isdigit.asp

Python String isdigit() Method

Python Examples Python Compiler ... Python Interview Q&A Python Training ... The isdigit() method returns True if all the characters are digits, otherwise False....

Python

docs.python.org › 3 › builtins › stdtypes.html

Built-in Types — Python 3.14.7 documentation

>>> '0123456789'.isdigit() True >>> '٠١٢٣٤٥٦٧٨٩'.isdigit() # Arabic-Indic digits zero to nine True >>> '⅕'.isdigit() # Vulgar fraction one fifth False >>> '²'.isdecimal(), '²'.isdigit(), '²'.isnumeric() (False, True, True)

Discussions

creating a function like isdigit() in python - Stack Overflow

Please don't give me the answer just point me in the right direction, thank you. Also, I need to do this without isdigit(). I am trying to create a program that checks all the characters of a stri... More on stackoverflow.com

stackoverflow.com

For single-char strings, Strings' .isdigit() method is about 7% slower than simply checking ```if string in "0123456789"```. Possible bug?

This susprised me because I assumed that the algorithm behind STRING.isdigit() is essentially a for loop that goes through each character of the string to check if it's a member of "0123456789". That is incorrect, isdigit() checks against the entire "Decimal Digit" Unicode category (Nd) which has hundreds of code points in it. So 7% slower is not bad. To be fair that's a common mistake, its behavior is really not what it looks like at first glance. More on reddit.com

r/Python

June 17, 2020

How To use isdigit in python

Hello, today i wanted to make a tkinter program and i made an entry about age the i only wanted the entry to get int numebrs for age but i did anything but it didnt work i asked someone for help and she said that i need to use isdigit but she didnt say how to use it. i just want to know how ... More on discuss.python.org

discuss.python.org

August 18, 2024

What's the difference between str.isdigit(), isnumeric() and ...

These are some of the least useful ... of the Python API. We really need an isfloat and the poorly named isdecimal and isnumeric are easy confused with these. 2021-08-29T16:44:03.63Z+00:00 ... Good answer but it would have helped slightly in the reading if you listed them in logical order: isdecimal - isdigit - isnumeric ... More on stackoverflow.com

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