Python 列表list使用介绍

一组有序项目的集合
可变的数据类型【可进行增删改查】
列表中可以包含任何数据类型，也可包含另一个列表【可任意组合嵌套】
列表是以方括号“[]”包围的数据集合，不同成员以“,”分隔
列表可通过序号访问其中成员

定义

>>> l = [] #空列表
>>> l = [1,2,3]
>>> l = [1,2,3,['a','b']]
>>> l = list('linuxeye')
>>> l
['l', 'i', 'n', 'u', 'x', 'e', 'y', 'e']
>>> l = list(range(5))
>>> l
[0, 1, 2, 3, 4]
>>> l = '1;2;3;4;5'.split(';')
>>> l
['1', '2', '3', '4', '5']

内建函数list(a_sequence) 可以将一个序列转为列表

索引
正索引是编号是从左到右，0开始；负索引编号是从右往左，-1、-2 …；取范围值都是从左至右

>>> LanguageList = ['Python','Shell','Perl','PHP','java','C',"C++","Lisp"]
>>> LanguageList[0] #取第一个值
'Python'
>>> LanguageList[3] #第四个值
'PHP'
>>> LanguageList[3:]
['PHP', 'java', 'C', 'C++', 'Lisp']
>>> LanguageList[:3]
['Python', 'Shell', 'Perl']
>>> LanguageList[2:5]
['Perl', 'PHP', 'java']

>>> LanguageList[-1] #倒数第一个值
'Lisp'
>>> LanguageList[-2] #倒数第二个值
'C++'
>>> LanguageList[-5:]
['PHP', 'java', 'C', 'C++', 'Lisp']
>>> LanguageList[-5:-2]
['PHP', 'java', 'C']
>>> LanguageList[:-2]
['Python', 'Shell', 'Perl', 'PHP', 'java', 'C']

增加元素

>>> LanguageList
['Python', 'Shell', 'Perl', 'PHP', 'java', 'C', 'C++', 'Lisp']
>>> LanguageList.append('GO')
>>> LanguageList
['Python', 'Shell', 'Perl', 'PHP', 'java', 'C', 'C++', 'Lisp', 'GO']
>>> LanguageList.insert(3,'Python') #往PHP元素前插入
>>> LanguageList
['Python', 'Shell', 'Perl', 'Python', 'PHP', 'java', 'C', 'C++', 'Lisp', 'GO']
>>> LanguageList.extend(['Ruby','C#'])
>>> LanguageList
['Python', 'Shell', 'Perl', 'Python', 'PHP', 'java', 'C', 'C++', 'Lisp', 'GO', 'Ruby', 'C#']

搜索

>>> LanguageList = ['Python', 'Shell', 'Perl', 'Python', 'PHP', 'java', 'C', 'C++', 'Lisp', 'GO', 'Ruby', 'C#']
>>> LanguageList.index('Python')
0
>>> LanguageList.index('C')
6
>>> LanguageList.index('c')
Traceback (most recent call last):
 File "<stdin>", line 1, in <module>
ValueError: list.index(x): x not in list
>>> 'c' in LanguageList
False
>>> LanguageList.index('Python') #统计一个元素的出现次数
2

删除元素

>>> LanguageList = ['Python', 'Shell', 'Perl', 'Python', 'PHP', 'java', 'C', 'C++', 'Lisp', 'GO', 'Ruby', 'C#']
>>> LanguageList.remove('C')
>>> LanguageList.remove('Python')
>>> LanguageList.remove('c')
Traceback (most recent call last):
 File "<stdin>", line 1, in <module>
ValueError: list.remove(x): x not in list
>>> LanguageList.pop()
'C#'
>>> LanguageList
['Shell', 'Perl', 'Python', 'PHP', 'java', 'C++', 'Lisp', 'GO', 'Ruby']
>>> LanguageList.pop(-2)
['Shell', 'Perl', 'Python', 'PHP', 'java', 'C++', 'Lisp', 'Ruby']
>>> del LanguageList[-3:-1]
>>> LanguageList
['Shell', 'Perl', 'Python', 'PHP', 'java', 'Ruby']

remove从列表中只删除一个值的首次出现。
pop会做两件事: 删除列表的最后一个元素, 然后返回删除元素的值。

修改元素

>>> LanguageList = ['Python','Shell', 'Perl', 'Python', 'PHP', 'java', 'Ruby']
>>> LanguageList[-2] = 'C'
>>> LanguageList
['Python', 'Shell', 'Perl', 'Python', 'PHP', 'C', 'Ruby']
>>> LanguageList[LanguageList.index('C')] = 'JAVA'
>>> LanguageList
['Python', 'Shell', 'Perl', 'Python', 'PHP', 'JAVA', 'Ruby']

运算符

>>> LanguageList
['Shell', 'Perl', 'Python', 'PHP', 'java', 'C++', 'Lisp', 'GO', 'Ruby']
>>> LanguageList = LanguageList + ['Python','C']
>>> LanguageList
['Shell', 'Perl', 'Python', 'PHP', 'java', 'C++', 'Lisp', 'GO', 'Ruby', 'Python', 'C']
>>> LanguageList += ['java']
>>> LanguageList
['Shell', 'Perl', 'Python', 'PHP', 'java', 'C++', 'Lisp', 'GO', 'Ruby', 'Python', 'C', 'java']
>>> NumList = [1,2,3] * 3
>>> NumList
[1, 2, 3, 1, 2, 3, 1, 2, 3]

排序

>>> NumList = [2,5,3,6,1,4]
>>> NumList.reverse()
>>> NumList
[4, 1, 6, 3, 5, 2]
>>> NumList[::-1] #和reverse效果相同
>>> NumList
[2, 5, 3, 6, 1, 4]
>>> NumList.sort()
>>> NumList
[1, 2, 3, 4, 5, 6]