python3 面向对象编程知识点介绍

简阶

这里的内容全部来自《python3 面向对象编程》，我将会把里面重要的知识点和案例代码贴出来。

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第1章 面向对象设计

第2章 Python 对象

第3章 对象相似时

第4章 异常捕获

第5章 何时使用面向对象编程

第6章 Python 数据结构

第7章 Python 面向对象的捷径

python 上下文管理器 （with 语法）

class StringJoiner(list):

    def __enter__(self):
        return self

    def __exit__(self, exc_type, exc_val, exc_tb):
        self.result = "".join(self)


import random, string

with StringJoiner() as joiner:
    for i in range(15):
        joiner.append(random.choice(string.ascii_letters))

print(joiner.result)

// 输出结果 >> LkWmGMSUxicWFzB

第8章 字符串与序列化

字符串格式化

# 字符串格式化
template = 'Hello {}, you are currently {}.'
print(template.format('Dusty', 'writing'))


template = 'Hello {0}, you are {1}. Your name is {0}.'
print(template.format('Dusty', 'writing',))

# 跳过花括号
template = '''
public class {0} {{
    public static void main(String[] args) {{
        System.out.println("{1}");
    }}
}}
'''
print(template.format('MyClass', 'print(\\"hello world\\")'))

# 关键字参数
template = """
From: <{from_email}>
To: <{to_email}>
subject: {subject}

{message}"""
print(template.format(
    from_email="a@example.com",
    to_email="b@example.com",
    message="Here's some mail for you. "
    " Hope you enjoy the message!",
    subject="You have mail!"
    ))

print("{} {label} {}".format("x", "y", label="z"))

# 字典参数 python2.7 不支持
phonebook = {'Beth': '9102', 'Alice': '2341', 'Cecil': '3258'}
print("Cecil's phone number is {Cecil}.".format_map(phonebook))

第9章 迭代器模式

第10章 Python 设计模式I

Python的装饰器模式

方法log_calls 是装饰器，test_* 是被装饰的方法

import time

def log_calls(func):
    def wrapper(*args, **kwargs):
        now = time.time()
        print("Calling {0} with {1} and {2}".format(
            func.__name__, args, kwargs
        ))
        return_value = func(*args, **kwargs)
        print("Executed {0} in {1}ms".format(
            func.__name__, time.time() - now
        ))
        return return_value
    return wrapper

def test_1(a, b, c):
    print("\ttest_1 called")

def test_2(a, b):
    print("\ttest_2 called")

def test_3(a, b):
    print("\ttest_3 called")
    time.sleep(1)

test_1 = log_calls(test_1)
test_2 = log_calls(test_2)
test_3 = log_calls(test_3)

test_1(1, 2, 3)
test_2(4, b=5)
test_3(6, 7)

输出结果：
Calling test_1 with (1, 2, 3) and {}
test_1 called
Executed test_1 in 7.82012939453125e-05ms
Calling test_2 with (4,) and {‘b’: 5}
test_2 called
Executed test_2 in 1.6927719116210938e-05ms
Calling test_3 with (6, 7) and {}
test_3 called
Executed test_3 in 1.0050618648529053ms

另一种语法

@log_calls
def test_1(a, b, c):
    print("\ttest_1 called")

test_1(1, 2, 3)

观察者模式

class Inventory:

    def __init__(self):
        self.observers = []
        self._product = None
        self._quantity = 0

    def attach(self, observer):
        self.observers.append(observer)

    @property
    def product(self):
        return self._product

    @product.setter
    def product(self, value):
        self._product = value
        self._update_observers()

    @property
    def quantity(self):
        return self._quantity

    @quantity.setter
    def quantity(self, value):
        self._quantity = value
        self._update_observers()

    def _update_observers(self):
        for observer in self.observers:
            observer()


class ConsoleObserver:

    def __init__(self, inventory):
        self.inventory = inventory

    def __call__(self):
        print(self.inventory.product)
        print(self.inventory.quantity)


if __name__ == '__main__':
    i = Inventory()
    c = ConsoleObserver(i)
    i.attach(c)
    i.product = 'widget'
    i.quantity = 5
    c1 = ConsoleObserver(i)
    i.attach(c1)
    i.product = 'Gadget'

第11章 Python 设计模式II

第12章 测试面向对象程序

第13章 并发