How to check if a variable is an integer or a string? [duplicate]

by

In my opinion you have two options:

  • Just try to convert it to an int, but catch the exception:

    try:
    value = int(value)
except ValueError:
    pass  # it was a string, not an int.

    This is the Ask Forgiveness approach.

  • Explicitly test if there are only digits in the string:

    value.isdigit()

    str.isdigit() returns True only if all characters in the string are digits (0–9).

    The unicode / Python 3 str type equivalent is unicode.isdecimal() / str.isdecimal(); only Unicode decimals can be converted to integers, as not all digits have an actual integer value (U+00B2 SUPERSCRIPT 2 is a digit, but not a decimal, for example).

    This is often called the Ask Permission approach, or Look Before You Leap.

The latter will not detect all valid int() values, as whitespace and + and - are also allowed in int() values. The first form will happily accept ' +10 ' as a number, the latter won’t.

If your expect that the user normally will input an integer, use the first form. It is easier (and faster) to ask for forgiveness rather than for permission in that case.

More Related Contents:

  1. How references to variables are resolved in Python [duplicate]
  2. how to parse the response in python?
  3. How to add a label to all words in a file? [closed]
  4. Python 2.7 IndentationError [closed]
  5. How to rename a file in python
  6. UnboundLocalError on local variable when reassigned after first use
  7. How to detect key presses?
  8. How to get the value of a variable given its name in a string? [duplicate]
  9. Using both Python 2.x and Python 3.x in IPython Notebook
  10. Getting an instance name inside class __init__() [duplicate]
  11. List vs generator comprehension speed with join function [duplicate]
  12. Launch a completely independent process
  13. Why does str(float) return more digits in Python 3 than Python 2?
  14. Add pygame module in PyCharm IDE
  15. How to pass an operator to a python function?
  16. How to get FTP file’s modify time using Python ftplib
  17. Passing data between separately running Python scripts
  18. How to pass dictionary items as function arguments in python? [duplicate]
  19. R and Python in one Jupyter notebook
  20. How to resume file download in Python?
  21. How to obtain values of request variables using Python and Flask [duplicate]
  22. Only add to a dict if a condition is met
  23. Generate list of months between interval in python
  24. Mixing files and loops
  25. Read Outlook Events via Python
  26. TypeError: cannot perform reduce with flexible type
  27. Python: How to resize an image using PIL module
  28. Python not able to open file with non-english characters in path
  29. How to fix TypeError: ‘int’ object is not subscriptable
  30. ‘is’ operator behaves unexpectedly with floats

Leave a Comment