Question

When I define a class and create an instance of it, entering the instance name into the shell returns a memory location. No surprise there, but does anybody know how to define a class in such a way that entering its name into a shell will actually return something other than a memory location?

Example:

>> import numpy as np
>> foo = np.array([1,2,3])
>> foo
>> array([1, 2, 3])

It would be nice if I could get something like this going.

Answer 1

This is what the __repr__ method is for:

>>> class point(object):
...     def __init__(self, x, y):
...         self.x = x
...         self.y = y
...         
...     def __repr__(self):
...         return "point(%d, %d)" % (self.x, self.y)
>>> x = point(3, 4)
>>> x
point(3, 4)

In the absence of a custom __repr__ implementation, you’ll see exactly what you’re describing in the question:

>>> class defaultPoint(object):
...     def __init__(self, x, y):
...         self.x = x
...         self.y = y  
... 
>>> p = defaultPoint(0, 3)
>>> p
<__main__.defaultPoint object at 0x16767b0>