Does python `str()` function call `__str__()` function of a class?

Question

If I define a class with its own __str__() function, is str(a) equivalent to a.__str__(), where a is an instance of my cl

Answer 1

Yes, it does. Take a look at the following example:

>>> class A:
...     def __init__(self, a):
...         self.a = a
...     def __str__(self):
...         print "Inside __str__"
...         return self.a
...
>>>
>>> a = A('obj1')
>>> a
<__main__.A instance at 0x0000000002605548>
>>>
>>> a.__str__()
Inside __str__
'obj1'
>>>
>>> str(a)
Inside __str__
'obj1'

And, from __str__() documentation, we have:

object.__str__(self)

Called by str(object) and the built-in functions format() and print() to compute the “informal” or nicely printable string representation of an object. The return value must be a string object.