list的用法（列表）
1.list函数可以把字符串切割成list
In [2]: arr = list(‘python‘) In [3]: arr Out[3]: [‘p‘, ‘y‘, ‘t‘, ‘h‘, ‘o‘, ‘n‘]
2.遍历list
In [7]: for i in [‘a‘,‘b‘,‘c‘]: ...: print(i) ...: a b c
3.长度，最大值，最小值
In [12]: arr = [1,3,5,-2,-8,357] In [13]: print(len(arr)) 6 In [14]: print(max(arr)) 357 In [15]: print(min(arr)) -8
4.del删除list中的元素
In [17]: arr Out[17]: [1, 3, 5, -2, -8, 357] In [18]: arr = [‘c++‘,‘c‘,‘java‘,‘html‘] In [19]: del arr[2] In [20]: print(arr) [‘c++‘, ‘c‘, ‘html‘]
5.list可以做乘法
In [8]: arr = [‘js‘,‘python‘,‘css‘,‘html‘] In [9]: arr * 2 Out[9]: [‘js‘, ‘python‘, ‘css‘, ‘html‘, ‘js‘, ‘python‘, ‘css‘, ‘html‘] In [10]: arr1 = [‘mon‘,‘tus‘] In [11]: arr + arr1 Out[11]: [‘js‘, ‘python‘, ‘css‘, ‘html‘, ‘mon‘, ‘tus‘
6.修改值和切片
In [21]: arr= [‘c‘,‘python‘,‘css‘,‘js‘,‘html‘,‘node‘] In [22]: arr[0] Out[22]: ‘c‘ In [23]: arr[-1] Out[23]: ‘node‘ In [24]: arr[1] Out[24]: ‘python‘ In [25]: arr[-3] Out[25]: ‘js‘
7.切片---获取list中一部分连续的数据
>>>arr= [‘c‘,‘python‘,‘css‘,‘js‘,‘html‘,‘node‘] >>>print arr[1:3] [‘python‘,‘css‘] >>>print arr[0:1] [‘c‘] >>>print arr[-1:-3] [] >>>print arr[-3:-1] [‘js‘,‘html‘]In [26]: arr= [‘c‘,‘python‘,‘css‘,‘js‘,‘html‘,‘node‘]In [27]: print(arr[1:3])[‘python‘, ‘css‘]In [28]: print(arr[0:1])[‘c‘]In [29]: print(arr[-1:-4])[]In [30]: print(arr[-1:-3])[]In [31]: print(arr[-3:-1])[‘js‘, ‘html‘]In [32]: print(arr[3:]) [‘js‘, ‘html‘, ‘node‘]In [33]: print(arr[::])[‘c‘, ‘python‘, ‘css‘, ‘js‘, ‘html‘, ‘node‘]In [34]: print(arr[:3])[‘c‘, ‘python‘, ‘css‘] >>>print arr[-3:] [‘js‘,‘html‘, ‘node‘] >>>print arr[3:] [‘js‘,‘html‘, ‘node‘] >>>print arr[:3] [‘c‘,‘python‘, ‘css‘] >>>print arr[:] [‘c‘,‘python‘, ‘css‘, ‘js‘, ‘html‘, ‘node‘]
8.切片可以赋值
In [35]: arr Out[35]: [‘c‘, ‘python‘, ‘css‘, ‘js‘, ‘html‘, ‘node‘] In [36]: arr[2:4]=[‘pc‘,‘wd‘] In [37]: arr Out[37]: [‘c‘, ‘python‘, ‘pc‘, ‘wd‘, ‘html‘, ‘node‘]
9.切片的赋值功能可以插模拟入和删除元素
In [39]: arr Out[39]: [‘c‘, ‘python‘, ‘pc‘, ‘wd‘, ‘html‘, ‘node‘] In [40]: arr[1:1]= [‘pc‘,‘wd‘] In [41]: arr Out[41]: [‘c‘, ‘pc‘, ‘wd‘, ‘python‘, ‘pc‘, ‘wd‘, ‘html‘, ‘node‘] In [42]: arr[2:3]= [] In [43]: arr Out[43]: [‘c‘, ‘pc‘, ‘python‘, ‘pc‘, ‘wd‘, ‘html‘, ‘node‘]
10.append 向list 最后追加元素
In [44]: arr= [‘wd‘,‘woniu‘,‘lp‘] In [45]: arr.append(‘suiji‘) In [46]: arr Out[46]: [‘wd‘, ‘woniu‘, ‘lp‘, ‘suiji‘]
11.count统计list中某个元素出现的次数
In [47]: arr= [2,3,4,5,6,7,8,9,43,24,234,423,423,12,2,3,4,52,2] In [48]: arr.count(2) Out[48]: 3
12.冒泡排序
In [49]: arr= [1,2,3,123,11,123,421,124,2,3,4,5,6] In [50]: for i in range(len(arr)-1): ....: for l in range(len(arr)-1-i): ....: if arr[l]>arr[l+1]: ....: arr[l],arr[l+1]=arr[l+1],arr[l] ....: In [51]: arr Out[51]: [1, 2, 2, 3, 3, 4, 5, 6, 11, 123, 123, 124, 421]
13.extend扩展源列表（修改了原列表，没有返回值）
In [53]: b = [7,8,9,2] In [54]: a = [1,2,3] In [55]: b = [4,5,6] In [56]: a.extend(b) In [57]: b.extend(a) In [58]: a Out[58]: [1, 2, 3, 4, 5, 6] In [59]: b Out[59]: [4, 5, 6, 1, 2, 3, 4, 5, 6]
14.index从列表中找出某个值，返回第一个匹配项的索引位置
In [60]: arr= [2,‘b‘,3,‘c‘,2,4,7] In [61]: arr.index(‘b‘) Out[61]: 1 In [62]: arr.index(‘c‘) Out[62]: 3
15.insert插队arr.insert(位置，插入的内容) 突然来了一个美女，要插队，大家都不好意思拒绝
In [63]: arr= [1,2,3,4,5,6,7] In [64]: arr.insert(3,‘four‘) In [65]: arr Out[65]: [1, 2, 3, ‘four‘, 4, 5, 6, 7]
16.pop根据索引移除list中的元素，并且返回，默认删除最后一个（不传参数的话，和append正好相反，pop是唯一一个即修改了源列表，又有返回值的方法）
In [66]: arr= [1,2,3,4] In [67]: arr.pop() Out[67]: 4 In [68]: arr Out[68]: [1, 2, 3] In [69]: arr= [1,2,3,4] In [70]: arr.pop(2) Out[70]: 3 In [71]: arr Out[71]: [1, 2, 4]
17.remove 根据值来删除元素，删除第一个匹配项（如果没有匹配项，报错）
In [74]: arr= [‘a‘,‘b‘,‘c‘,‘d‘] In [75]: arr.remove(‘a‘) In [76]: arr Out[76]: [‘b‘, ‘c‘, ‘d‘] #remove如果没有匹配到则抛出ValueError的异常 In [77]: arr.remove(‘asdf‘)----------------------------------- ValueError: list.remove(x): x not in list
18.reverse LIST 反向修改列表，不返回值
In [78]: arr= [1,2,3,4] In [79]: arr.reverse() In [80]: arr Out[80]: [4, 3, 2, 1]
19.sort方法用于排序，修改list本身
In [81]: arr= [-11,2,1,5] In [82]: arr.sort() In [83]: arr Out[83]: [-11, 1, 2, 5]
dict的一些方法
时间： 2024-10-29 11:52:49