Python操作列表的常用方法分享
下面列出列表常用的方法操作列表以及小例子：
1. Append
在列表末尾添加元素，需在列表末尾添加元素，需要注意几个点:
A.append中添加的参数是作为一个整体
>>>name=list("scott")
>>>name
["s","c","o","t","t"]
>>>name.append(list("tiger"))
>>>name
["s","c","o","t","t",["","t","i","g","e","r"]]
得到的值不是：["s","c","o","t","t","","t","i","g","e","r"]
如果想要这种的追加方式，可以试试分片赋值(或者下面说到的extend方法)：
>>>name=list("scott")
>>>name
["s","c","o","t","t"]
>>>name[len(name):]=list("tiger") #从末尾追加
>>>name
["s","c","o","t","t","","t","i","g","e","r"]
B.append一次性只能添加一个元素
>>>name=list("scott")
>>>name
["s","c","o","t","t"]
>>>name.append("A","B") #添加多个元素即将报错
Traceback(mostrecentcalllast):
File"<stdin>",line1,in?
TypeError:append()takesexactlyoneargument(2given)
>>>name.append("A")
>>>name
["s","c","o","t","t","A"]
2.Count
统计某个元素在列表中出现的次数
>>>name=list("scott")
>>>name
["s","c","o","t","t"]
>>>name.count("s")
1
>>>name.count("t")
2
>>>name.count("A")
0
>>>name.append(list("Python"))
>>>name
["s","c","o","t","t",["P","y","t","h","o","n"]]
>>>name.count(["P","y","t","h","o","n"])
1
3.Extend
在原列表追加另一个序列的中的多个值
当然，我们可以用分片赋值来实现： 这时小伙伴们会想到，我们可以直接用操作符"+"嘛，还方便些： 从这三种方式操作的输出，可以看出： 从输出可以看出，index找的是第一个匹配项的索引位置，而如果查找的元素不在列表中，会报错（返回-1会不会好一点呢?），当然如果想避免报 我们也可以用分片赋值： 这里需要注意的是，如果是插入一个元素，需要用[]括起来，不然，直接用字符串的话，是插入字符串的列表，在索引位置之后添加。 这上面用pop和append模拟了栈的先进先出LIFO。 将列表中的元素反向 sort方法用于对列表进行排序，修改原列表，不会返回一个已排序的列表副本 如果我们想要返回一个已排序的列表副本，而不影响原来的列表呢，一种方法，我们可以先赋值原来列表（可以用分片赋值复制），然后
>>>name=list("scott")
>>>name
["s","c","o","t","t"]
>>>name.extend(list("tiger"))
>>>name
["s","c","o","t","t","","t","i","g","e","r"]
>>>name=list("scott")
>>>name
["s","c","o","t","t"]
>>>name[len(name):]=list("tiger")
>>>name
["s","c","o","t","t","","t","i","g","e","r"]
>>>name=list("scott")
>>>pwd =list("tiger")
>>>name+pwd
["s","c","o","t","t","","t","i","g","e","r"]
>>>name
["s","c","o","t","t"]
extend和分片赋值都是修改原列表，相对而言，extend可读性强些，而操作符"+"是生成一个新的列表，不影响原列表，如果
我们需要生成新列表而不影响原列表，就可以用操作符"+"。
4.Index
从列表中找出某个值第一个（注意是第一个）匹配项的索引位置
>>>name=list("scott")
>>>name
["s","c","o","t","t"]
>>>name.index("t") ##第一个字母t的索引位置是3
3
>>>name.index("a")
Traceback(mostrecentcalllast):
File"<stdin>",line1,in?
ValueError:list.index(x):xnotinlist
>>>"a"inname
False
>>>"a"notinname
True
错，我们可以先用in操作，判断某个元素是否在某个列表中，如果在的话，然后进行index操作。
5.Insert
用于将对象插入到列表中，俩个参数，第一个是索引位置，第二个插入的元素对象。
>>>name=list("scott")
>>>name
["s","c","o","t","t"]
>>>name.insert(2,"tiger") ##在索引为2的地方插入字符串tiger
>>>name
["s","c","tiger","o","t","t"]
>>>name=list("scott")
>>>name
["s","c","o","t","t"]
>>>name[2:2]=["tiger"]
>>>name
["s","c","tiger","o","t","t"]
>>>name[2:2]="tiger"
>>>name
["s","c","t","i","g","e","r","tiger","o","t","t"]
当然，用insert的可读性比分片赋值强。
6.Pop
移除列表中的一个元素（最后一个元素），并返回该元素的值
>>>name=list("scott")
>>>name
["s","c","o","t","t"]
>>>name.pop()
"t"
>>>name
["s","c","o","t"]
>>>name.append("t")
>>>name
["s","c","o","t","t"]
分片赋值模拟pop:
>>>name=list("scott")
>>>name
["s","c","o","t","t"]
>>>name[len(name)-1:]=[]
>>>name
["s","c","o","t"]
7.Remove
移除列表中某个值的第一匹配项：如果有俩个相等的元素，就只是移除匹配的一个元素，如果某元素不存在某列表中，便会报错，而且一次性只能
移除一个元素。
>>>name=list("scott")
>>>name
["s","c","o","t","t"]
>>>name.remove("t") #去掉第一个t
>>>name
["s","c","o","t"]
>>>name.remove("A") #不存在会报错
Traceback(mostrecentcalllast):
File"<stdin>",line1,in?
ValueError:list.remove(x):xnotinlist
>>>"A"notinname
True
>>>name.remove("s","c") #一次只能移除一个元素
Traceback(mostrecentcalllast):
File"<stdin>",line1,in?
TypeError:remove()takesexactlyoneargument(2given)
8.Revense
>>>name=list("scott")
>>>name
["s","c","o","t","t"]
>>>name.reverse()
>>>name
["t","t","o","c","s"]
9.Sort&Sorted
>>>result=[8,5,5,3,9]
>>>result.sort()
>>>result
[3,5,5,8,9]
在复制的列表上做sort操作，另一种方法，就是使用sorted函数，它会返回已排序的列表副本：
>>>result=[8,5,5,3,9]
>>>result2=sorted(result)
>>>result
[8,5,5,3,9]
>>>result2
[3,5,5,8,9]
关于自定义的比较方法，像javascript做sort可以传入compare函数，java可以传入Comparable<T>实例，Python也类似，留待后续了~(@^_^@)~。
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