Testing for a list

[Mark McEahern]

[Antun Karlovac]
> Is there a way to test if a variable is a list?
>
> i.e.
>
>   a = []
>
> If I have 'a', I need to know whether it is a list or a string.

Here's a unittest-demo of the code Alex posted here:

  http://groups.google.com/groups?selm=hi018.2207%24Qu1.90579%40news2.tin.it

#!/usr/bin/env python

import unittest

def issequence(item):
    try:
        item + ''
    except TypeError:
        try:
            for x in item:
                break
        except TypeError:
            return False
        else:
            return True
    else:
        return False

class test(unittest.TestCase):

    def test_unicode(self):
        u = u'test'
        self.failIf(issequence(u))

    def test_string(self):
        s = 'string'
        self.failIf(issequence(s))

    def test_list(self):
        l = []
        self.failUnless(issequence(l))

    def test_tuple(self):
        t = ()
        self.failUnless(issequence(t))

if __name__ == '__main__':
    unittest.main()

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