Python学习笔记 第二课 循环

 >>> movies=["The Holy Grail", 1975, "The Life of Brian", 1979, "The Meaning of Life", 1983]
 >>> for eachMovie in movies:
     print(eachMovie)

按下两个回车后输出结果如下：

 The Holy Grail
 1975
 The Life of Brian
 1979
 The Meaning of Life
 1983

列表中还可以存储其他列表！

movies = ["The Holy Grail", 1975, "Terry Jones & Terry Gilliam", 91,
        　　["Graham Chapman",
      　　　　["Michael Palin", "John Cleese", "Terry Gilliam", "Eric Idle", "Terry Jones"]
　　　　　　 ]
　　　　　 ]

这样的嵌套列表用上面的for循环怎么处理呢？

>>> for each_item in movies:
    print(each_item)

The Holy Grail
1975
Terry Jones & Terry Gilliam
91
['Graham Chapman', ['Michael Palin', 'John Cleese', 'Terry Gilliam', 'Eric Idle', 'Terry Jones']]

哦！没有处理干净......

再循环！

>>> for each_item in movies:
    if isinstance(each_item,list):
        for nested_item in each_item:
            if isinstance(nested_item,list):
                for deeper_item in nested_item:
                    if isinstance(deeper_item,list):
                        for deepest_item in deeper_item:
                            print(deepest_item)
                    else:
                        print(deeper_item)
            else:
                print(nested_item)
    else:
        print(each_item)

The Holy Grail
1975
Terry Jones & Terry Gilliam
91
Graham Chapman
Michael Palin
John Cleese
Terry Gilliam
Eric Idle
Terry Jones

哇塞!这倒是处理干净了，但是也太绕了吧！不过队形不错！

用函数来处理

def 函数名（参数）:

　　函数代码组

 >>> def print_lol(movies):
     for each_item in movies:
         if isinstance(each_item,list):
             print_lol(each_item)
         else:
             print(each_item)

6行代码即可完成上面的晕头转向。

引用函数：

>>> print_lol (movies)

结果如下：

 The Holy Grail
 1975
 Terry Jones & Terry Gilliam
 91
 Graham Chapman
 Michael Palin
 John Cleese
 Terry Gilliam
 Eric Idle
 Terry Jones

我们以后就可以用这个函数来处理各种嵌套列表了。

定义一个列表：

>>> hello=["a","b",1,3,["hello",22,33,["ok","h"]],"zhuangshi"]

调用函数：

>>> print_lol(hello)

结果如下：

 a
 b
 1
 3
 hello
 22
 33
 ok
 h
 zhuangshi

再看这个函数：

 >>> def print_lol(movies):
     for each_item in movies:
         if isinstance(each_item,list):
             print_lol(each_item)
         else:
             print(each_item)

在代码内部引用了自身！——递归！没错是递归。Python3默认递归深度不能超过100，但是这个深度上限可以改。

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