python基础教程学习记录

最近在看的是《python 基础教程》，第九章的小知识点比较多，记录一下课本上的示例，都是手敲过一遍的加深一下印象。

主要介绍了类相关的内容，迭代器，生成器等基础知识。

# super方法class Bird:    def __init__(self):        self.hungry = True    def eat(self):        if self.hungry:            print('Ahaaa...')            self.hungry = False        else:            print('No Thanks')class SongBird(Bird):    def __init__(self):        # 如果没有super这行调用父类构造方法，则无法访问父类的eat函数和成员hungry        # 出现错误AttributeError: 'SongBird' object has no attribute 'hungry'        super(SongBird, self).__init__()        self.sound = 'Squawk!'    def sing(self):        print(self.sound)sb = SongBird()sb.sing()sb.eat()  # Ahaaa...sb.eat()  # No Thanks# 成员访问，基本的序列和映射规则__len__（self）,__getitem__(self,key),,def checkIndex(key):    if not isinstance(key, (int, int)): raise TypeError    if key < 0:        raise IndexErrorclass ASquence:    def __init__(self, start=0, step=1):        """        初始化算术序列，        """        self.start = start        self.step = step        self.changed = {}     def __getitem__(self, key):        """        该方法返回与所给键对应的值        """        checkIndex(key)        try:            return self.changed[key]  # 修改了吗？        except KeyError:            return self.start + key * self.step  # 计算值    def __setitem__(self, key, value):        """        按一定的崔则存储和key相关的value,该值随后可使用__getitem__来获取        """        checkIndex(key)        self.changed[key] = value  # 保存修改后的值s = ASquence(1, 2)print(s[4])  # 9s[4] = 2print(s[4])  # 2print(s[5])  # 11# 子类化列表，字典和字符串# 如果希望实现一个和内建列表行为类似的序列，可以子类化list来实现class CounterList(list):    def __init__(self, *args):        super(CounterList, self).__init__(*args)        self.counter = 0    def __getitem__(self, index):        self.counter += 1        return super(CounterList, self).__getitem__(index)c1 = CounterList(range(10))print(c1)  # [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]c1.reverse()print(c1)  # [9, 8, 7, 6, 5, 4, 3, 2, 1, 0]del c1[3:6]  # [9, 8, 7, 3, 2, 1, 0]print(c1)print(c1.counter)  # 0c1[4] + c1[2]  # 每次列表中的元素被访问，counter就会自增，所以下面为2print(c1.counter)  # 2print(c1[3])print(c1.counter)  # 3# property函数"""property有0，1，2，3，4个参数，fget,fset,fdel,doc,可以用关键字参数设置其中若干个eg property(fset=**,doc=**)"""class Rectangle:    def __init__(self):        self.width = 0        self.height = 0    def setSize(self, size):        self.width, self.height = size    def getSize(self):        return self.width, self.height    size = property(getSize, setSize)  # 可以直接使用size而不用调用getSize/setSizer = Rectangle()r.width = 10r.height = 5print(r.size)  # (10, 5)r.size = 150, 100print(r.size)  # (150, 100)# 静态方法和类成员函数"""可以使用装饰器描述"""class MyClass:    @staticmethod    def smeth():        print('This is a static method')    @classmethod    def cmeth(cls):  # 类成员方法需要cls类似于self        print('This is a class of ', cls)MyClass.smeth()  # This is a static methodMyClass.cmeth()  # This is a class of  <class '__main__.MyClass'># __getattr__,__setattr__# 迭代器__iter__,返回一个迭代器，具有next方法"""在3.0中，迭代器需要实现__next__方法，并使用next访问，next(it)等于2.X版本中的it.next()"""class Fibs:    def __init__(self):        self.a = 0        self.b = 1    def __next__(self):        self.a, self.b = self.b, self.a + self.b        return self.a    def __iter__(self):        return selffibs = Fibs()for f in fibs:    if f > 100:        print(f)  # 144        break# 从迭代器得到序列class TestIter:    value = 0    def __next__(self):        self.value += 1        if self.value > 10: raise StopIteration        return self.value    def __iter__(self):        return selfti = TestIter()print(list(ti))  # [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]# 生成器'''生成器是一个包含yield关键字的函数，当它被调用时，在函数体中的代码不会被执行，而会返回一个迭代器，每次请求一个值，就会执行生成器中的代码，知道遇到一个yield或者return语句，yield语句意味着生成一个值，return语句意味着生成器要停止。'''def flattern(nested):    try:        for sublist in nested:            for elem in flattern(sublist):                yield elem    except TypeError:        yield nestedprint(list(flattern([[[1], 2], 3, 4, [5, [6, 7]], 8])))  # [1, 2, 3, 4, 5, 6, 7, 8]