output formatting for user-defined types

[Peter Hansen]

Russ wrote:
> I'd like to get output formatting for my own classes that mimics the
> built-in output formatting. For example,
> 
> 
>>>>x = 4.54
>>>>print "%4.2f" % x
> 
> 
> 4.54
> 
> In other words, if I substitute a class instance for "x" above, I'd
> like to make the format string apply to an element or elements of the
> instance. Is that possible? If so, how? Thanks.

I believe implementing the special method __float__ on your class 
should be sufficient.	

class X:
   def __float__(self):
     return 3.14

 >>> print '%f' % X()
3.140000

-Peter