How can I print a Python class?

Question

I have a class that contains several functions(most of it contains code that parses smth., get all necessary info and print it). I'm trying to print a class but i get smth. like <_main_.TestClass instance at 0x0000000003650888>. Code sample:

from lxml import html
import urllib2
url = 'someurl.com'


class TestClass:

    def testFun(self):
        f = urllib2.urlopen(url).read()
        #some code

        print 'Value for ' +url+ ':', SomeVariable

    def testFun2(self):
        f2 = urllib2.urlopen(url).read()
        #some code

        print 'Value2 for ' +url+ ':', SomeVariable2

test = TestClass()
print test

When i print functions out of class - all is ok. What i'm doing wrong and how can I print a class?

Thanks!

score 7 · Accepted Answer · answered Feb 19 '13 at 07:28

That's the expected behaviour. Python can't know how the class is represented unless you define a __str__ or __repr__ method to give the class a string representation.

To be clear: __repr__ is usually defined to produce a string that can be evaluated back into a similar object (in your case, TestClass()). The default __repr__ prints out the <__main__.TestClass instance at 0xdeadbeef> thing you see.

Example __repr__:

def __repr__(self):
    return self.__class__.__name__ + '()' # put constructor arguments in the ()

__str__ can be defined to produce a human-readable "description" of the class. If not supplied, you get __repr__.

Example __str__:

def __str__(self):
    return "(TestClass instance)"

`0xdeadbeef` if you hit this memory location Ill buy you a stake — Jakob Bowyer, Feb 19 '13 at 09:30

score 1 · Answer 2 · answered Feb 19 '13 at 07:29

1

It looks like you want to print an instance of the class rather than the class itself. Define a __str__ or __repr__ method that returns a string to be used when printing the instance.

See: http://docs.python.org/2/reference/datamodel.html#object.__repr__

http://docs.python.org/2/reference/datamodel.html#object.__str__

answered Feb 19 '13 at 07:29

samfrances

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Thanks for the answer and additional info! – Alex A Feb 19 '13 at 07:45

How can I print a Python class?

2 Answers2