Lec21-Representation

2024-10-20 161 words One minute

Contents

Representation

Strings

一个是Python表达式（解释器可以直接运行的形式），一个是字符串（人类可读的形式）

repr

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>>> s = 'hello'
>>> print(repr(s))
'hello'

>>> repr(min)
'<built-in function min>'

str

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>>> from fractions import Fraction
>>> half = Fraction(1, 2)
>>> print(half) # calls __str__
1/2
>>> repr(half) # calls __repr__
'Fraction(1, 2)'
>>> eval(repr(half)) # creates a new Fraction object
Fraction(1, 2)

F-Strings

{ }里面的按照表达式来计算

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>>> x = 10
>>> y = 20
>>> f"x + y = {x + y}"
'x + y = 30'

多态函数

Functions that apply to many different forms of data…

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>>> half.__repr__()
'Fraction(1, 2)'
>>> half.__str__()
'1/2'

实现 __repr__ 和 __str__ 方法

__repr__: Only class attributes are found! Ignore instance attributes.
__str__: Ignore instance attributes. If no __str__ method is defined, it will use __repr__ method.

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def repr(obj):
    return type(obj).__repr__(obj)

Interfaces

类似61B的课程，实现接口（长得像是__xx__）

喜欢Java 😋

special methods

群贤毕至

终于和cmu 10-414对上了

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