13.17. OOP Stringify Repr

• Calling function repr(obj) calls obj.__repr__()

• Method obj.__repr__() must return str

• Dedicated for developers

• Shows object representation

• Copy-paste for creating object with the same values

• Useful for debugging

• Printing list will call __repr__() method on each element

13.17.1. Inherited

Object without __repr__() method overloaded prints their memory address:

>>> class User:
...     def __init__(self, firstname, lastname):
...         self.firstname = firstname
...         self.lastname = lastname
...
...
>>> mark = User('Mark', 'Watney')

>>> mark  
<__main__.User object at 0x10aef7450>

>>> repr(mark)  
'<__main__.User object at 0x10aef7450>'

>>> mark.__repr__()  
'<__main__.User object at 0x10aef7450>'

>>> f'{mark!r}'  
'<__main__.User object at 0x10aef7450>'

13.17.2. Overloaded

>>> class User:
...     def __init__(self, firstname, lastname):
...         self.firstname = firstname
...         self.lastname = lastname
...
...     def __repr__(self):
...         firstname = self.firstname
...         lastname = self.lastname
...         return f'User({firstname=}, {lastname=})'
...
...
>>> mark = User('Mark', 'Watney')

>>> mark
User(firstname='Mark', lastname='Watney')

>>> repr(mark)
"User(firstname='Mark', lastname='Watney')"

>>> mark.__repr__()
"User(firstname='Mark', lastname='Watney')"

>>> f'{mark!r}'
"User(firstname='Mark', lastname='Watney')"

13.17.3. Assignments

Code 13.25. Solution

"""
* Assignment: OOP Stringify Repr
* Required: yes
* Complexity: easy
* Lines of code: 3 lines
* Time: 5 min

English:
    1. Overload `repr()`
    2. Run doctests - all must succeed

Polish:
    1. Przeciąż `repr()`
    2. Uruchom doctesty - wszystkie muszą się powieść

Tests:
    >>> import sys; sys.tracebacklimit = 0
    >>> from inspect import isclass, ismethod

    >>> assert isclass(Iris)
        >>> iris = Iris(DATA)

    >>> assert hasattr(Iris, '__repr__')
    >>> assert ismethod(iris.__repr__)
    >>> repr(iris)
    "Iris(features=[4.7, 3.2, 1.3, 0.2], label='setosa')"
"""

DATA = (4.7, 3.2, 1.3, 0.2, 'setosa')


# repr() -> Iris(features=[4.7, 3.2, 1.3, 0.2], label='setosa')
class Iris:
    features: list
    label: str

    def __init__(self, data):
        self.features = list(data[:-1])
        self.label = str(data[-1])