How do you check in python whether a string contains only numbers

Question

How do you check whether a string contains only numbers   I ve given it a go here  I d like to see the simplest way to accomplish this   import string  def main        isbn   input  Enter your 10 digit ISBN number         if len isbn     10 and string digits    True          print   Works       else          print  Error  10 digit number was not inputted and or letters were inputted            main    if   name         main         main       input  Press enter to exit

User · Answer

As pointed out in this comment How do you check in python whether a string contains only numbers? the isdigit() method is not totally accurate for this use case, because it returns True for some digit-like characters:

>>> "\u2070".isdigit() # unicode escaped 'superscript zero' 
True

If this needs to be avoided, the following simple function checks, if all characters in a string are a digit between "0" and "9":

import string

def contains_only_digits(s):
    # True for "", "0", "123"
    # False for "1.2", "1,2", "-1", "a", "a1"
    for ch in s:
        if not ch in string.digits:
            return False
    return True

Used in the example from the question:

if len(isbn) == 10 and contains_only_digits(isbn):
    print ("Works")

User · Answer

Use str isdigit    gt  gt  gt   12345  isdigit   True  gt  gt  gt   12345a  isdigit   False  gt  gt  gt

User · Answer

There are 2 methods that I can think of to check whether a string has all digits of not  Method 1 Using the built-in isdigit   function in python  -   gt  gt  gt st    12345   gt  gt  gt st isdigit   True  gt  gt  gt st    1abcd   gt  gt  gt st isdigit   False   Method 2 Performing Exception Handling on top of the string  -  st  1abcd  try      number int st      print  String has all digits in it   except      print  String does not have all digits in it     The output of the above code will be   String does not have all digits in it

User · Answer

Use string isdigit function    gt  gt  gt  s    12345   gt  gt  gt  s isdigit   True  gt  gt  gt  s    1abc   gt  gt  gt  s isdigit   False

User · Answer

You ll want to use the isdigit method on your str object  if len isbn     10 and isbn isdigit     From the isdigit documentation   str isdigit   Return True if all characters in the string are digits and there is at least one character  False otherwise  Digits include decimal characters and digits that need special handling  such as the compatibility superscript digits  This covers digits which cannot be used to form numbers in base 10  like the Kharosthi numbers  Formally  a digit is a character that has the property value Numeric Type Digit or Numeric Type Decimal

User · Answer

You can also use the regex    import re   eg -1  word    3487954   re match    0-9     word    eg -2  word    3487 954   re match    0-9       word    eg -3  word    3487 954 328   re match    0-9         word    As you can see all 3 eg means that there is only no in your string  So you can follow the respective solutions given with them

User · Answer

What about of float numbers  negatives numbers  etc   All the examples before will be wrong    Until now I got something like this  but I think it could be a lot better    95 95  replace        1  isdigit     will return true only if there is one or no     in the string of digits    9 5 9 5  replace        1  isdigit     will return false

User · Answer

You can use try catch block here   s  1234  try      num int s      print  S contains only digits  except      print  S doesn t contain digits ONLY

User · Answer

As every time I encounter an issue with the check is because the str can be None sometimes  and if the str can be None  only use str isdigit   is not enough as you will get an error      AttributeError   NoneType  object has no attribute  isdigit    and then you need to first validate the str is None or not  To avoid a multi-if branch  a clear way to do this is   if str and str isdigit      Hope this helps for people have the same issue like me

User · Answer

you can use str isdigit   method or str isnumeric   method

[python] How do you check in python whether a string contains only numbers?

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