String Representation

Describing String Representations

• The class method __format__() has the following properties:

  • Called by the format() function
  • In other words, format just calls obj.__format__
  • Provides the object with a format method that performs some formatting operation
  • Can be thought of as syntactic sugar

• The class method __repr__() has the following properties:

  • Its goal is to be unambiguous
  • Should be implemented for any class to provide the class with a useful identity

• The class method __str__() has the following properties:

  • Its goal is to be readable
  • Can be implemented if there is a more readable string representation
• The following class uses these special methods:

>>> class Document: 
...     def __init__(self, words): 
...         self.words = words
...     def __repr__(self):
...         t = ''
...         for i in self.words:
...            t = t + i + '\n'
...         return t
...     def __str__(self):
...         return 'Document: ' + self.words 

>>> d = Document('my doc')
>>> d
m
y

d
o
c

>>> repr(d)
'm\ny\n \nd\no\nc\n'
>>> str(d)
'Document: my doc'

Summarizing Special Methods

References

• Python Essential Reference
• Use-Cases for Each Special Method
• Description of the format Special Method
• Example of format Special Method