数据类型--列表
列表概念
列表又称：list是处理一组有序项目的数据结构，即你可以在一个列表中存储一个序列的项目。
List（列表） 是 Python 中使用最频繁的数据类型。列表可以完成大多数集合类的数据结构实现。
列表用 “ [ ] " 标识。是python最通用的复合数据类型，它支持字符，数字，字符串甚至可以包含列表（所谓嵌套）。
列表中的值得分割，也可以用到变量[头下标:尾下标]，又称切片。
它可以截取相应的列表，从左到右索引默认0开始的，从右到左索引默认-1开始。
下标可以为空表示取到头或尾。
加号（+）是列表连接运算符，星号（*）是重复操作。
要点
列表是可变类型的数据。
列表的组成：用[]表示列表，包含了多个以逗号分隔开的数字，或者字符串。
列表与元祖的区别：操作基本一样，唯一区别就是元祖值不可变更。
例如：
1 list1=['Simon','David','Clotho','张三'] 2 list2=[1,2,3,4,5] 3 list3=["str1","str2","str3","str4","str5"]
列表的用法
基本操作：
索引
切片
追加
删除
长度
切片
循环
包含
1 list = [ 'abcd', 786 , 2.23, 'john', 70.2 ] 2 tinylist = [123, 'john'] 3 4 print(list) # 输出完整列表 5 print(list[0]) # 输出列表的第一个元素 6 print(list[1:3]) # 输出第二个至第三个的元素 7 print(list[2:]) # 输出从第三个开始至列表末尾的所有元素 8 print(tinylist * 2) # 输出列表两次 9 print(list + tinylist) # 打印组合的列表 10 11 输出结果： 12 ['abcd', 786, 2.23, 'john', 70.2] 13 abcd 14 [786, 2.23] 15 [2.23, 'john', 70.2] 16 [123, 'john', 123, 'john'] 17 ['abcd', 786, 2.23, 'john', 70.2, 123, 'john']
列表的其他参数
1 class list(object): 2 """ 3 list() -> new empty list 4 list(iterable) -> new list initialized from iterable's items 5 """ 6 def append(self, p_object): # real signature unknown; restored from __doc__ 7 """ L.append(object) -- append object to end """ 8 pass 9 10 def count(self, value): # real signature unknown; restored from __doc__ 11 """ L.count(value) -> integer -- return number of occurrences of value """ 12 return 0 13 14 def extend(self, iterable): # real signature unknown; restored from __doc__ 15 """ L.extend(iterable) -- extend list by appending elements from the iterable """ 16 pass 17 18 def index(self, value, start=None, stop=None): # real signature unknown; restored from __doc__ 19 """ 20 L.index(value, [start, [stop]]) -> integer -- return first index of value. 21 Raises ValueError if the value is not present. 22 """ 23 return 0 24 25 def insert(self, index, p_object): # real signature unknown; restored from __doc__ 26 """ L.insert(index, object) -- insert object before index """ 27 pass 28 29 def pop(self, index=None): # real signature unknown; restored from __doc__ 30 """ 31 L.pop([index]) -> item -- remove and return item at index (default last). 32 Raises IndexError if list is empty or index is out of range. 33 """ 34 pass 35 36 def remove(self, value): # real signature unknown; restored from __doc__ 37 """ 38 L.remove(value) -- remove first occurrence of value. 39 Raises ValueError if the value is not present. 40 """ 41 pass 42 43 def reverse(self): # real signature unknown; restored from __doc__ 44 """ L.reverse() -- reverse *IN PLACE* """ 45 pass 46 47 def sort(self, cmp=None, key=None, reverse=False): # real signature unknown; restored from __doc__ 48 """ 49 L.sort(cmp=None, key=None, reverse=False) -- stable sort *IN PLACE*; 50 cmp(x, y) -> -1, 0, 1 51 """ 52 pass 53 54 def __add__(self, y): # real signature unknown; restored from __doc__ 55 """ x.__add__(y) <==> x+y """ 56 pass 57 58 def __contains__(self, y): # real signature unknown; restored from __doc__ 59 """ x.__contains__(y) <==> y in x """ 60 pass 61 62 def __delitem__(self, y): # real signature unknown; restored from __doc__ 63 """ x.__delitem__(y) <==> del x[y] """ 64 pass 65 66 def __delslice__(self, i, j): # real signature unknown; restored from __doc__ 67 """ 68 x.__delslice__(i, j) <==> del x[i:j] 69 70 Use of negative indices is not supported. 71 """ 72 pass 73 74 def __eq__(self, y): # real signature unknown; restored from __doc__ 75 """ x.__eq__(y) <==> x==y """ 76 pass 77 78 def __getattribute__(self, name): # real signature unknown; restored from __doc__ 79 """ x.__getattribute__('name') <==> x.name """ 80 pass 81 82 def __getitem__(self, y): # real signature unknown; restored from __doc__ 83 """ x.__getitem__(y) <==> x[y] """ 84 pass 85 86 def __getslice__(self, i, j): # real signature unknown; restored from __doc__ 87 """ 88 x.__getslice__(i, j) <==> x[i:j] 89 90 Use of negative indices is not supported. 91 """ 92 pass 93 94 def __ge__(self, y): # real signature unknown; restored from __doc__ 95 """ x.__ge__(y) <==> x>=y """ 96 pass 97 98 def __gt__(self, y): # real signature unknown; restored from __doc__ 99 """ x.__gt__(y) <==> x>y """ 100 pass 101 102 def __iadd__(self, y): # real signature unknown; restored from __doc__ 103 """ x.__iadd__(y) <==> x+=y """ 104 pass 105 106 def __imul__(self, y): # real signature unknown; restored from __doc__ 107 """ x.__imul__(y) <==> x*=y """ 108 pass 109 110 def __init__(self, seq=()): # known special case of list.__init__ 111 """ 112 list() -> new empty list 113 list(iterable) -> new list initialized from iterable's items 114 # (copied from class doc) 115 """ 116 pass 117 118 def __iter__(self): # real signature unknown; restored from __doc__ 119 """ x.__iter__() <==> iter(x) """ 120 pass 121 122 def __len__(self): # real signature unknown; restored from __doc__ 123 """ x.__len__() <==> len(x) """ 124 pass 125 126 def __le__(self, y): # real signature unknown; restored from __doc__ 127 """ x.__le__(y) <==> x<=y """ 128 pass 129 130 def __lt__(self, y): # real signature unknown; restored from __doc__ 131 """ x.__lt__(y) <==> x<y """ 132 pass 133 134 def __mul__(self, n): # real signature unknown; restored from __doc__ 135 """ x.__mul__(n) <==> x*n """ 136 pass 137 138 @staticmethod # known case of __new__ 139 def __new__(S, *more): # real signature unknown; restored from __doc__ 140 """ T.__new__(S, ...) -> a new object with type S, a subtype of T """ 141 pass 142 143 def __ne__(self, y): # real signature unknown; restored from __doc__ 144 """ x.__ne__(y) <==> x!=y """ 145 pass 146 147 def __repr__(self): # real signature unknown; restored from __doc__ 148 """ x.__repr__() <==> repr(x) """ 149 pass 150 151 def __reversed__(self): # real signature unknown; restored from __doc__ 152 """ L.__reversed__() -- return a reverse iterator over the list """ 153 pass 154 155 def __rmul__(self, n): # real signature unknown; restored from __doc__ 156 """ x.__rmul__(n) <==> n*x """ 157 pass 158 159 def __setitem__(self, i, y): # real signature unknown; restored from __doc__ 160 """ x.__setitem__(i, y) <==> x[i]=y """ 161 pass 162 163 def __setslice__(self, i, j, y): # real signature unknown; restored from __doc__ 164 """ 165 x.__setslice__(i, j, y) <==> x[i:j]=y 166 167 Use of negative indices is not supported. 168 """ 169 pass 170 171 def __sizeof__(self): # real signature unknown; restored from __doc__ 172 """ L.__sizeof__() -- size of L in memory, in bytes """ 173 pass 174 175 __hash__ = None
列表的练习：
1 names = ['a','b','c','d','e','f'] 2 ########切片######## 3 print(names[1:4]) 4 print(names[:4]) 5 print(names[2],names[4]) 6 print(names[1:3]) #起始位置包含本身，结束为不包含本身，需要往后+1位。 7 print(names[0:3]) 8 print("取前单3个值",names[:3]) 9 print(names[-1]) #取最后一个 10 print(names[-3:]) #取最后三个 11 print(names[-2:]) #取最后两个 12 13 显示结果： 14 ['b', 'c', 'd'] 15 ['a', 'b', 'c', 'd'] 16 c e 17 ['b', 'c'] 18 ['a', 'b', 'c'] 19 取前单3个值 ['a', 'b', 'c'] 20 f 21 ['d', 'e', 'f'] 22 ['e', 'f'] 23 24 25 26 ########追加##########： 27 print('='.center(50,'=')) 28 names.append("c") 29 names.append("d") 30 names.append("b") 31 print(names) 32 33 显示结果： 34 ['a', 'b', 'c', 'd', 'e', 'f', 'c', 'd', 'b'] 35 36 37 38 39 ########指定位置插入######## 40 print('='.center(50,'=')) 41 names.insert(2,"w") 42 names.insert(4,"k") 43 names.insert(6,"w") 44 names.insert(9,"r") 45 names.insert(10,"w") 46 names.insert(13,"w") 47 print(names) 48 49 显示结果： 50 ['a', 'b', 'w', 'c', 'k', 'd', 'w', 'e', 'f', 'r', 'w', 'c', 'd', 'w', 'b'] 51 52 53 54 ########更改######## 55 print('='.center(50,'=')) 56 names[0] = 2 57 names[3] = 3 58 print(names) 59 60 显示结果： 61 [2, 'b', 'w', 3, 'k', 'd', 'w', 'e', 'f', 'r', 'w', 'c', 'd', 'w', 'b'] 62 63 64 65 ########删除######## 66 names.remove(2) #按照元素名称删除 67 print(names) 68 69 del names[2] #按照下标的位置删除 70 print(names) 71 72 names.pop() #从后往前删 73 print(names) 74 75 names.pop(7) #删除第7位的数值 76 print(names) 77 78 79 显示结果： 80 ['b', 'w', 3, 'k', 'd', 'w', 'e', 'f', 'r', 'w', 'c', 'd', 'w', 'b'] 81 ['b', 'w', 'k', 'd', 'w', 'e', 'f', 'r', 'w', 'c', 'd', 'w', 'b'] 82 ['b', 'w', 'k', 'd', 'w', 'e', 'f', 'r', 'w', 'c', 'd', 'w'] 83 ['b', 'w', 'k', 'd', 'w', 'e', 'f', 'w', 'c', 'd', 'w'] 84 85 86 87 ########索引######## 88 print(names.index("w")) 89 90 #表里的元素过多，但是只知道某一个元素的名字，然后通过元素的名字取索引的位置。 91 print(names.index("d")) 92 93 #已知上面的位置，找到相对应的名字。 94 print(names[names.index("d")]) 95 96 ########查找重复元素的个数######## 97 print(names.count("w")) 98 99 ########清理重复的字符######## 100 for i in range(names.count("w")): 101 names.remove("w") 102 else: 103 print("循环删除",names) 104 105 显示结果： 106 3 107 d 108 循环删除 ['b', 'k', 'd', 'e', 'f', 'c', 'd'] 109 110 111 112 ########清理列表######## 113 names.clear() 114 print(names) 115 116 显示结果： 117 [] 118 119 120 121 ########反转######## 122 names.reverse() 123 print(names) 124 125 ######排序######## 126 names.insert(3,"#") 127 names.insert(8,"!@2@#") 128 print(names) 129 names.sort() 130 print(names) 131 132 133 显示结果： 134 ['d', 'c', 'f', 'e', 'd', 'k', 'b'] 135 ['d', 'c', 'f', '#', 'e', 'd', 'k', 'b', '!@2@#'] 136 ['!@2@#', '#', 'b', 'c', 'd', 'd', 'e', 'f', 'k'] 137 138 139 140 141 ######反转######## 142 name2 = [1,2,3,4] 143 names.extend(name2) 144 print(names,name2) 145 146 names+name2 147 print(names,name2) 148 149 显示结果： 150 ['!@2@#', '#', 'b', 'c', 'd', 'd', 'e', 'f', 'k', 1, 2, 3, 4] [1, 2, 3, 4] 151 ['!@2@#', '#', 'b', 'c', 'd', 'd', 'e', 'f', 'k', 1, 2, 3, 4] [1, 2, 3, 4] 152 153 154 names = ['a', 'b', '赵',['alex','jack'],'d', 'd', 'e', 'f'] 155 156 ######循环列表###### 157 for i in names: 158 print(i) 159 160 #######按照步长来切片###### 161 #range(1,10,2)从1--10每个2个打印一次 162 print(names[0:-1:2]) 163 164 ######0和-1都可以省略掉###### 165 print(names[::2]) 166 167 显示结果： 168 a 169 b 170 赵 171 ['alex', 'jack'] 172 d 173 d 174 e 175 f 176 ['a', '赵', 'd', 'e'] 177 ['a', '赵', 'd', 'e']
