Python3--列表

列表

本节重点

1.理解列表数据类型出现的意义
2.掌握列表的定义和特性
3.熟练掌握列表常用操作，并了解其他工厂方法
4.认识range方法，并能将range方法产生的数据转换成列表

列表定义和创建

定义

[]内以逗号分割，按照索引，存放各种数据类型，每个位置代表一个元素

列表的创建

 

list_test = ['张三'，'李思'，'樵夫']

#或

list_test = list('李思')

#或

list_test = list(['张三'，'李思'，'樵夫'])

 

列表的特点

特性

1.可以存放多个值
2.按照从左到右的顺序定义列表元素，下标从0开始顺序访问，有序
3.可以修改指定位置对应的值，可变

常用操作

#作用：多个装备，多个爱好，多门课程，多个女朋友等

#定义：[]内可以有多个任意类型的值，逗号分隔
my_girl_friends=['alex','wupeiqi','yuanhao',4,5] #本质my_girl_friends=list([...])
或
l=list('abc')

#优先掌握的操作：
#1、按索引存取值(正向存取+反向存取)：即可存也可以取      
#2、切片(顾头不顾尾，步长)
#3、长度
#4、成员运算in和not in

#5、追加
#6、删除
#7、循环

列表工厂函数（源码）

class list(object):
    """
    list() -> new empty list
    list(iterable) -> new list initialized from iterable's items
    """在数组的末尾新增一项
    def append(self, p_object): # real signature unknown; restored from __doc__
        """
        L.append(object) -- append object to end """
        pass

    def count(self, value): # real signature unknown; restored from __doc__
        """ 查看lst中某一项出现的次数
        L.count(value) -> integer -- return number of occurrences of value """
        return 0

    def extend(self, iterable): # real signature unknown; restored from __doc__
        """将原列表与其他列表扩展成新列表
        L.extend(iterable) -- extend list by appending elements from the iterable """
        pass

    def index(self, value, start=None, stop=None): # real signature unknown; restored from __doc__
        """返回列表中第一个匹配项的下标，找不到会报错
        L.index(value, [start, [stop]]) -> integer -- return first index of value.
        Raises ValueError if the value is not present.
        """
        return 0

    def insert(self, index, p_object): # real signature unknown; restored from __doc__
        """在指定位置插入项
        L.insert(index, object) -- insert object before index """
        pass

    def pop(self, index=None): # real signature unknown; restored from __doc__
        """返回指定位置的值，并将其从列表中删除。默认对末尾项操作
        L.pop([index]) -> item -- remove and return item at index (default last).
        Raises IndexError if list is empty or index is out of range.
        """
        pass

    def remove(self, value): # real signature unknown; restored from __doc__
        """从列表中移除第一个符合与指定值相等的项
        L.remove(value) -- remove first occurrence of value.
        Raises ValueError if the value is not present.
        """
        pass

    def reverse(self): # real signature unknown; restored from __doc__
        """列表反转
        L.reverse() -- reverse *IN PLACE* """
        pass

    def sort(self, cmp=None, key=None, reverse=False): # real signature unknown; restored from __doc__
        """排序，数字、字符串按照ASCII，中文按照unicode从小到大排序。
        L.sort(cmp=None, key=None, reverse=False) -- stable sort *IN PLACE*;
        cmp(x, y) -> -1, 0, 1
        """
        pass

    def __add__(self, y): # real signature unknown; restored from __doc__
        """ 字符串拼接
        x.__add__(y) <==> x+y """
        pass

    def __contains__(self, y): # real signature unknown; restored from __doc__
        """ 判断列表中是否包含某一项
        x.__contains__(y) <==> y in x """
        pass

    def __delitem__(self, y): # real signature unknown; restored from __doc__
        """删除列表中指定下标的项
        x.__delitem__(y) <==> del x[y] """
        pass

    def __delslice__(self, i, j): # real signature unknown; restored from __doc__
        """删除指定下标之间的内容，向下包含
        x.__delslice__(i, j) <==> del x[i:j]
                   
                   Use of negative indices is not supported.
        """
        pass

    def __eq__(self, y): # real signature unknown; restored from __doc__
        """ 判断两个列表是否相等
        x.__eq__(y) <==> x==y """
        pass

    def __getattribute__(self, name): # real signature unknown; restored from __doc__
        """ 无条件被调用，通过实例访问属性。
        x.__getattribute__('name') <==> x.name """
        pass

    def __getitem__(self, y): # real signature unknown; restored from __doc__
        """ x.__getitem__(y) <==> x[y] """
        pass

    def __getslice__(self, i, j): # real signature unknown; restored from __doc__
        """
        x.__getslice__(i, j) <==> x[i:j]
                   
                   Use of negative indices is not supported.
        """
        pass

    def __ge__(self, y): # real signature unknown; restored from __doc__
        """ x.__ge__(y) <==> x>=y """
        pass

    def __gt__(self, y): # real signature unknown; restored from __doc__
        """ x.__gt__(y) <==> x>y """
        pass

    def __iadd__(self, y): # real signature unknown; restored from __doc__
        """ x.__iadd__(y) <==> x+=y """
        pass

    def __imul__(self, y): # real signature unknown; restored from __doc__
        """ 
        x.__imul__(y) <==> x*=y """
        pass

    def __init__(self, seq=()): # known special case of list.__init__
        """
        list() -> new empty list
        list(iterable) -> new list initialized from iterable's items
        # (copied from class doc)
        """
        pass

    def __iter__(self): # real signature unknown; restored from __doc__
        """ x.__iter__() <==> iter(x) """
        pass

    def __len__(self): # real signature unknown; restored from __doc__
        """ x.__len__() <==> len(x) """
        pass

    def __le__(self, y): # real signature unknown; restored from __doc__
        """ x.__le__(y) <==> x<=y """
        pass

    def __lt__(self, y): # real signature unknown; restored from __doc__
        """ x.__lt__(y) <==> x<y """
        pass

    def __mul__(self, n): # real signature unknown; restored from __doc__
        """ x.__mul__(n) <==> x*n """
        pass

    @staticmethod # known case of __new__
    def __new__(S, *more): # real signature unknown; restored from __doc__
        """ T.__new__(S, ...) -> a new object with type S, a subtype of T """
        pass

    def __ne__(self, y): # real signature unknown; restored from __doc__
        """ x.__ne__(y) <==> x!=y """
        pass

    def __repr__(self): # real signature unknown; restored from __doc__
        """ x.__repr__() <==> repr(x) """
        pass

    def __reversed__(self): # real signature unknown; restored from __doc__
        """ L.__reversed__() -- return a reverse iterator over the list """
        pass

    def __rmul__(self, n): # real signature unknown; restored from __doc__
        """ x.__rmul__(n) <==> n*x """
        pass

    def __setitem__(self, i, y): # real signature unknown; restored from __doc__
        """ x.__setitem__(i, y) <==> x[i]=y """
        pass

    def __setslice__(self, i, j, y): # real signature unknown; restored from __doc__
        """
        x.__setslice__(i, j, y) <==> x[i:j]=y
                   
                   Use  of negative indices is not supported.
        """
        pass

    def __sizeof__(self): # real signature unknown; restored from __doc__
        """ L.__sizeof__() -- size of L in memory, in bytes """
        pass

    __hash__ = None

列表与字符串--split和join

#分割
>>> s = 'hello world'

>>> s.split(' ')

['hello','world']

>>> s2 = 'hello,world'

>>> s2.split(',')

#连接
>>> l = ['hi','樵夫']

>>> '!'.join(l)

'hi!樵夫'

range

>>> list(range(10))

[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]

>>> list(range(1,10))

[1, 2, 3, 4, 5, 6, 7, 8, 9]

>>> list(range(0,10,2)) 

[0, 2, 4, 6, 8]

练习

1. 有列表data=['alex',49,[1900,3,18]]，分别取出列表中的名字，年龄，出生的年，月，日赋值给不同的变量

2. 用列表模拟队列

3. 用列表模拟堆栈

4. 有如下列表，请按照年龄排序（涉及到匿名函数）
l=[
    {'name':'alex','age':84},
    {'name':'oldboy','age':73},
    {'name':'egon','age':18},
]
答案：
l.sort(key=lambda item:item['age'])
print(l)