[Tutor] Alter print action for objects

Jordan Greenberg jordangreenberg at gmail.com
Wed Jul 23 13:22:00 CEST 2008

Shrutarshi Basu wrote:
> I'm working on a graph class to become more familiar with graphs in
> general. I'd like to be able to do something like 'print gr'  and get
> something intelligible like a list of vertices. But using print on a
> Graph class instance simply returns <Graph instance at some_hex_addr>
> Is there someway I can change what print prints?

print will print the string returned by an object's __str__ method.
Try something like this:

In [1]: class Example(object):
    ...:     def __init__(self, x):
    ...:         self.x=x
    ...:     def __str__(self):
    ...:         return "x is: %s"%(self.x)

In [3]: ex=Example(5)

In [4]: print ex
x is: 5

The "basic customization" page in the Python Reference Manual may be of 
use as well: http://docs.python.org/ref/customization.html


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