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

Question

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

Answer 1

Python 2

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

Docs.

Answer 2

In order to check if your variable is something you could go like:

s='Hello World'
if isinstance(s,str):
#do something here,

The output of isistance will give you a boolean True or False value so you can adjust accordingly. You can check the expected acronym of your value by initially using: type(s) This will return you type 'str' so you can use it in the isistance function.

Answer 3

Python 2 and 3

(cross-compatible)

If you want to check with no regard for Python version (2.x vs 3.x), use six (PyPI) and its string_types attribute:

import six

if isinstance(obj, six.string_types):
    print('obj is a string!')

Within six (a very light-weight single-file module), it's simply doing this:

import sys
PY3 = sys.version_info[0] == 3

if PY3:
    string_types = str
else:
    string_types = basestring

Answer 4

For a nice duck-typing approach for string-likes that has the bonus of working with both Python 2.x and 3.x:

def is_string(obj):
    try:
        obj + ''
        return True
    except TypeError:
        return False

wisefish was close with the duck-typing before he switched to the isinstance approach, except that += has a different meaning for lists than + does.

Answer 5

if type(varA) == str or type(varB) == str:
    print 'string involved'

from EDX - online course MITx: 6.00.1x Introduction to Computer Science and Programming Using Python

Answer 6

You can test it by concatenating with an empty string:

def is_string(s):
  try:
    s += ''
  except:
    return False
  return True

Edit:

Correcting my answer after comments pointing out that this fails with lists

def is_string(s):
  return isinstance(s, basestring)