How to find out if a Python object is a string?

Python 2

Use isinstance(obj, basestring) for an object-to-test obj.

In Python 3.x basestring is not available anymore, as str is the sole string type (with the semantics of Python 2.x's unicode).

So the check in Python 3.x is just:

isinstance(obj_to_test, str)

This follows the fix of the official 2to3 conversion tool: converting basestring to str.

python string types compatibility

To check if an object o is a string type of a subclass of a string type:

isinstance(o, basestring)

because both str and unicode are subclasses of basestring.

To check if the type of o is exactly str:

type(o) is str

To check if o is an instance of str or any subclass of str:

isinstance(o, str)

The above also work for Unicode strings if you replace str with unicode.

However, you may not need to do explicit type checking at all. "Duck typing" may fit your needs. See http://docs.python.org/glossary.html#term-duck-typing.