Q:

How to compare type of an object in Python?

Basically I want to do this:
obj = 'str'
type ( obj ) == string

I tried:
type ( obj ) == type ( string )

and it didn't work.
Also, what about the other types? For example, I couldn't replicate NoneType.

A:

isinstance()

In your case, isinstance("this is a string", str) will return True.
You may also want to read this: http://www.canonical.org/~kragen/isinstance/

A:

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

but, keep in mind: if it looks like a duck, and if it sounds like a duck, it is a duck.
EDIT:  For the None type, you can simply do:
if obj is None: obj = MyClass()

A:

First, avoid all type comparisons.  They're very, very rarely necessary.  Sometimes, they help to check parameter types in a function -- even that's rare.  Wrong type data will raise an exception, and that's all you'll ever need.
All of the basic conversion functions will map as equal to the type function.
type(9) is int
type(2.5) is float
type('x') is str
type(u'x') is unicode
type(2+3j) is complex

There are a few other cases.
isinstance( 'x', basestring )
isinstance( u'u', basestring )
isinstance( 9, int )
isinstance( 2.5, float )
isinstance( (2+3j), complex )

None, BTW, never needs any of this kind of type checking.  None is the only instance of NoneType.  The None object is a Singleton.  Just check for None
variable is None

BTW, do not use the above in general.  Use ordinary exceptions and Python's own natural polymorphism.

