Telling what type of data is what, Python

Question

I would like to be able to tell if a variable is an int or not using an if statement in Python. How would I go about this.

There are no variables in Python, there are only objects and references to objects — eyquem, Feb 07 '11 at 08:20
@eyquem: There is no need to be formal here. Of course there are variables in Python, the term is used many times throughout the official documentation, e.g. http://docs.python.org/tutorial/introduction.html#numbers ("The equal sign ('=') is used to assign a value to a variable"). — Ferdinand Beyer, Feb 07 '11 at 08:42
The next question is: Why do you need to do that? Usually you shouldn't need to do any type checking in Python. [Use "duck typing" instead](http://stackoverflow.com/questions/1549801/differences-between-isinstance-and-type-in-python/1549854#1549854). — Tim Pietzcker, Feb 07 '11 at 08:59
@Tim Pietzcker: Thanks for pointing. I've deleted my answer. — Mudassir, Feb 07 '11 at 09:44

score 5 · Accepted Answer · answered Feb 07 '11 at 08:07

5

Use isinstance:

if isinstance(var, int):
  print "Int"
elif isinstance(var, str):
  print "Str"
else:
  print "Other:", type(var)

answered Feb 07 '11 at 08:07

Ferdinand Beyer

There is also the 'types' module that you could use to help! – Iacks Feb 07 '11 at 09:02

score 3 · Answer 2 · answered Feb 07 '11 at 08:08

3

if isinstance(x,int):
 print 'win'

answered Feb 07 '11 at 08:08

jbcurtin

score 2 · Answer 3 · answered Feb 07 '11 at 08:07

2

You just need to use isinstance:

value = 123
if isinstance(value, int):
    print "Int"
else:
    print "Not Int"

answered Feb 07 '11 at 08:07

Richard J

score 0 · Answer 4 · answered Jun 02 '13 at 13:30

If the question is to detect if a variable in bound to an int or a value of any derived type, so isinstance is the solution...

... but it does not distinguish between say int and bool. In Python 3:

>>> isinstance(123, int)
True
>>> isinstance(True, int)
True
>>> isinstance(123, bool)
False
>>> isinstance(True, bool)
True

If you really need to know if a value is an int and nothing else, type() should be the way to go:

>>> type(123)
<class 'int'>
>>> type(123) == int
True

4 Answers4