How to find out if a Python object a string?

Question

How can I check if a Python object is a string (either regular or Unicode)?

Answer 1

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

Docs.

Answer 2

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.

See also What’s the canonical way to check for type in python?

Answer 3

I might deal with this in the duck-typing style, like others mention. How do I know a string is really a string? well, obviously by converting it to a string!

def myfunc(word):
    word = unicode(word)
    ...

If the arg is already a string or unicode type, real_word will hold its value unmodified. If the object passed implements a __unicode__ method, that is used to get its unicode representation. If the object passed cannot be used as a string, the unicode builtin raises an exception.