How to determine the variable or object type in Python?

Question

I have some variables and I have to perform some operations on them based on the type of variable they are.
Is there a convenient way to check the type of variable in python?

Answer 1

In python there are two ways to identify the type of object -

• Using type(obj) method - which returns the type of variable passed as an argument.

  type([]) is list #True
  type({}) is dict #True
  type('') is str #True
  type(0) is int #True
  type({}) #
  type([]) #

This of course also works for custom types:

class Test1 (object):
        pass
class Test2 (Test1):
       pass
a = Test1()
b = Test2()
type(a) is Test1  #True
type(b) is Test2  #True

Note that type() will only return the immediate type of the object, but won’t be able to tell you about type inheritance.

type(b) is Test1  #False

• Using isinstance(obj, type) method - which returns whether the type of object is same as the type passed. This also tells you about type inheritance -

  isinstance(b, Test1) #True
  isinstance(b, Test2) #True
  isinstance(a, Test1) #True
  isinstance(a, Test2) #False
  isinstance([], list) #True
  isinstance({}, dict) #True

We generally prefer the isinstance() to ensure the type of an object because it will also accept derived types.

The second parameter of isinstance() also accepts a tuple of types, so it’s possible to check for multiple types at once. isinstance will then return true, if the object is of any of those types:

isinstance([], (tuple, list, set))  #True