check if a number is int or float

I like @ninjagecko's answer the most.

This would also work:

for Python 2.x

isinstance(n, (int, long, float)) 

Python 3.x doesn't have long

isinstance(n, (int, float))

there is also type complex for complex numbers

Use isinstance.

>>> x = 12
>>> isinstance(x, int)
True
>>> y = 12.0
>>> isinstance(y, float)
True

So:

>>> if isinstance(x, int):
        print('x is a int!')

x is a int!

In case of long integers, the above won't work. So you need to do:

>>> x = 12L
>>> import numbers
>>> isinstance(x, numbers.Integral)
True
>>> isinstance(x, int)
False

(note: this will return True for type bool, at least in cpython, which may not be what you want. Thank you commenters.)

One-liner:

isinstance(yourNumber, numbers.Real)

This avoids some problems:

>>> isinstance(99**10,int)
False

Demo:

>>> import numbers

>>> someInt = 10
>>> someLongInt = 100000L
>>> someFloat = 0.5

>>> isinstance(someInt, numbers.Real)
True
>>> isinstance(someLongInt, numbers.Real)
True
>>> isinstance(someFloat, numbers.Real)
True