On the IsDigit () Judgment of negative numbers

-->the start

Today's writing industry suddenly thought, has been using the IsDigit () method to handle the user's input selection is not a number, but if the user entered a negative, will not cause a bug?

Then I tried it and didn't give an error ... Then I was wondering, and I tried it a little bit:

' -10 '. IsDigit () returns false because '-' is not a digit.

Then I want to know how to judge negative numbers, here is the answer from the Internet, recorded here.

1 ' -10 ' 2 if (Num.startswith ('-'andor  num). IsDigit ():3     print(num is an integer)4Else:5     Print (num is not an integer)

Regular Expression method:

1 ' -10 ' 2 Import Re 3 if re.match (r'^-? \.\d+|\d+ (\.\d+)?) ' , num):4     print(num is an integer)5Else: 6     Print (num is not an integer)

A more pythonic approach:

1 ' -10 ' 2 if num.lstrip ('-'). IsDigit ():3     print (num is an integer) 4 Else : 5     Print (num is not an integer)

When I saw the third method, I was very touched and benefited.

<--the End

On the IsDigit () Judgment of negative numbers