Python – How to check if raw input is integer in python 2.7

integerpythonpython-2.7raw-inputstring

Is there a method that I can use to check if a raw_input is an integer?

I found this method after researching in the web:

print isinstance(raw_input("number: ")), int)

but when I run it and input 4 for example, I get FALSE.
I'm kind of new to python, any help would be appreciated.

Best Answer

isinstance(raw_input("number: ")), int) always yields False because raw_input return string object as a result.

Use try: int(...) ... except ValueError:

number = raw_input("number: ")
try:
    int(number)
except ValueError:
    print False
else:
    print True

or use str.isdigit:

print raw_input("number: ").isdigit()

NOTE The second one yields False for -4 because it contains non-digits character. Use the second one if you want digits only.

UPDATE As J.F. Sebastian pointed out, str.isdigit is locale-dependent (Windows). It might return True even int() would raise ValueError for the input.

>>> import locale
>>> locale.getpreferredencoding()
'cp1252'
>>> '\xb2'.isdigit()  # SUPERSCRIPT TWO
False
>>> locale.setlocale(locale.LC_ALL, 'Danish')
'Danish_Denmark.1252'
>>> '\xb2'.isdigit()
True
>>> int('\xb2')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: invalid literal for int() with base 10: '\xb2'

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