obj = 'str'
type ( obj ) == string

type ( obj ) == type ( string )

isinstance()

if isinstance(obj, MyClass): do_foo(obj)

if obj is None: obj = MyClass()

type(9) is int
type(2.5) is float
type('x') is str
type(u'x') is unicode
type(2+3j) is complex

isinstance( 'x', basestring )
isinstance( u'u', basestring )
isinstance( 9, int )
isinstance( 2.5, float )
isinstance( (2+3j), complex )

variable is None

>>> import types
>>> x = "mystring"
>>> isinstance(x, types.StringType)
True
>>> x = 5
>>> isinstance(x, types.IntType)
True
>>> x = None
>>> isinstance(x, types.NoneType)
True

# check if x is a regular string
type(x) == type('')
# check if x is an integer
type(x) == type(1)
# check if x is a NoneType
type(x) == type(None)

# check if x is a regular string
type(x) == str
# check if x is either a regular string or a unicode string
type(x) in [str, unicode]
# alternatively:
isinstance(x, basestring)
# check if x is an integer
type(x) == int
# check if x is a NoneType
x is None

type( x ) == type( [] )

type( x ) == type( '' ) or type( x ) == type( u'' )

x is None

s="hello"
type(s) == type("")

def firstElement(parameter):
    return parameter[0]

import types

def firstElement(parameter):
    if type(parameter) != types.TupleType:
         raise TypeError("function accepts only a tuple")
    return parameter[0]

def firstElement(parameter):
    if not (hasattr(parameter, "__getitem__") and callable(getattr(parameter,"__getitem__"))):
        raise TypeError("interface violation")
    return parameter[0]

def firstElement(parameter):
    if not (hasattr(parameter, "__getitem__") and callable(getattr(parameter,"__getitem__"))):
        raise TypeError("interface violation")
    os.system("rm file")
    return parameter[0]

if isinstance(obj, str)

type(obj) == str  # this works because str is already a type

type(obj) == type('')