Purpose of Python's __repr__

Question

def __repr__(self):
  return '<%s %s (%s:%s) %s>' % (
    self.__class__.__name__, self.urlconf_name, self.app_name,
    self.namespace, self.regex.pattern)

What is the significance/purpose of this method?

Answer 1

This is explained quite well in the Python documentation:

repr(object): Return a string containing a printable representation of an object. This is the same value yielded by conversions (reverse quotes). It is sometimes useful to be able to access this operation as an ordinary function. For many types, this function makes an attempt to return a string that would yield an object with the same value when passed to eval(), otherwise the representation is a string enclosed in angle brackets that contains the name of the type of the object together with additional information often including the name and address of the object. A class can control what this function returns for its instances by defining a __repr__() method.

So what you're seeing here is the default implementation of __repr__, which is useful for serialization and debugging.

Answer 2

__repr__ is used to print a human readable presentation of an object. In this case it prints the class name and some other attributes. A simple example:

>>> class Point:
...   def __init__(self, x, y):
...     self.x, self.y = x, y
...   def __repr__(self):
...     return 'Point(x=%s, y=%s)' % (self.x, self.y)
>>> p = Point(1, 2)
>>> p
Point(x=1, y=2)