Python之List

列表也是序列式的数据类型，可通过下标或切片操作来访问某一个或某一段连续的元素。

一、创建列表

列表可以由方括号'[]'来定义，通过赋予变量来创建。

>>> l1 = ['abc','456','xyz']
>>> l1
['abc', '456', 'xyz']

列表中可以再嵌套一个列表，像这样：

>>> l2 = ['abc','456','xyz',['789','lmn']]
>>> l2
['abc', '456', 'xyz', ['789', 'lmn']]

二、列表的操作

a.访问

采用切片操作与索引值方式来访问列表。

>>> l2
['abc', '456', 'xyz', ['789', 'lmn']]
>>> l2[0]
'abc'
>>> l2[-1]
['789', 'lmn']
>>> l2[3][1]
'lmn'

b.更新

使用append()方法来将追加元素到列表中。

>>> l1 = ['abc','456','xyz']
>>> l1.append('Li')
>>> l1
['abc', '456', 'xyz', 'Li']

三、几个有用的函数

1. len()

统计列表中元素的个数

>>> l3
['2', '3', '5', '6', '9']
>>> len(l3)
5

2. max()&min()

获取列表中最大与最小值

>>> max(l3)
'9'
>>> min(l3)
'2'

3. enumerate()

遍历序列中的元素以及它们的下标

>>> for i,j in enumerate([1,2,3]):
>>> print i,j 
0 1
1 2
2 3

4. sum

将列表中的值相加

>>> l4 = [int('2'),int('4')]
>>> sum(l4)
6

注：只能对整数和字符串类型进行相加，否则会出错

四、内置函数

    def append(self, p_object):
    #向列表中添加一个对象

    def clear(self): 
    #清空列表

    def copy(self): 
    #浅copy

    def count(self, value): 
    #统计一个对象在列表中出现的次数

    def extend(self, iterable): 
    #将内容添加到列表中
    >>> l1
    ['abc', '456', 'xyz', 'Li']
    >>> l1
    ['abc', '456', 'xyz', 'Li']
    >>> l2
    ['abc', '456', 'xyz', ['789', 'lmn']]
    >>> l1.extend(l2)
    >>> l1
    ['abc', '456', 'xyz', 'Li', 'abc', '456', 'xyz', ['789', 'lmn']]

    def index(self, value, start=None, stop=None): 
    #获取列表中的索引位置
        """       
    def insert(self, index, p_object): 
    #指定下标插入元素
    
    def pop(self, index=None): 
    #指定下标删除元素，并获取删除元素（如果没有指定对象，默认是最后一个值）

    def remove(self, value):
    #指定值删除的元素

    def reverse(self): 
    #反向列表中元素

    def sort(self, key=None, reverse=False): 
    #对列表中的元素进行排序
    >>> l3 = ['3','6','5','9','2']
    >>> l3.sort()
    >>> l3
    ['2', '3', '5', '6', '9']

    def __add__(self, *args, **kwargs): # real signature unknown
        """ Return self+value. """
        pass

    def __contains__(self, *args, **kwargs): # real signature unknown
        """ Return key in self. """
        pass

    def __delitem__(self, *args, **kwargs): # real signature unknown
        """ Delete self[key]. """
        pass

    def __eq__(self, *args, **kwargs): # real signature unknown
        """ Return self==value. """
        pass

    def __getattribute__(self, *args, **kwargs): # real signature unknown
        """ Return getattr(self, name). """
        pass

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

    def __ge__(self, *args, **kwargs): # real signature unknown
        """ Return self>=value. """
        pass

    def __gt__(self, *args, **kwargs): # real signature unknown
        """ Return self>value. """
        pass

    def __iadd__(self, *args, **kwargs): # real signature unknown
        """ Implement self+=value. """
        pass

    def __imul__(self, *args, **kwargs): # real signature unknown
        """ Implement self*=value. """
        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, *args, **kwargs): # real signature unknown
        """ Implement iter(self). """
        pass

    def __len__(self, *args, **kwargs): # real signature unknown
        """ Return len(self). """
        pass

    def __le__(self, *args, **kwargs): # real signature unknown
        """ Return self<=value. """
        pass

    def __lt__(self, *args, **kwargs): # real signature unknown
        """ Return self<value. """
        pass

    def __mul__(self, *args, **kwargs): # real signature unknown
        """ Return self*value.n """
        pass

    @staticmethod # known case of __new__
    def __new__(*args, **kwargs): # real signature unknown
        """ Create and return a new object.  See help(type) for accurate signature. """
        pass

    def __ne__(self, *args, **kwargs): # real signature unknown
        """ Return self!=value. """
        pass

    def __repr__(self, *args, **kwargs): # real signature unknown
        """ Return repr(self). """
        pass

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

    def __rmul__(self, *args, **kwargs): # real signature unknown
        """ Return self*value. """
        pass

    def __setitem__(self, *args, **kwargs): # real signature unknown
        """ Set self[key] to value. """
        pass

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

    __hash__ = None