Python数据类型：列表、集合、字典、字符串、元组和序列

Python数据类型：列表、集合、字典、字符串、元组和序列

1 列表（可变、有序）

1.1 定义

myList=list("data")
print(myList)

[‘d’, ‘a’, ‘t’, ‘a’]

1.2 切片

左闭右开

myList1[start:stop:step]
myList1[1:8:2]

1.3 反向遍历

1.3.1 切片操作

myList1=[21,22,23,24,25,26,27,28,29]
myList1[:-1]

[21, 22, 23, 24, 25, 26, 27, 28]

myList1=[21,22,23,24,25,26,27,28,29]
myList1[::-1]

[29, 28, 27, 26, 25, 24, 23, 22, 21]
此时，myList1=[21,22,23,24,25,26,27,28,29]
切片操作不会改变列表本身

1.3.2 内置函数reversed()

myList1=[21,22,23,24,25,26,27,28,29]
reversed(myList1)      #reversed()函数的返回值为一个迭代器，可以用list()强制转换的方式显示其取值内容
list(reversed(myList1))

[29, 28, 27, 26, 25, 24, 23, 22, 21]
此时，myList1=[21,22,23,24,25,26,27,28,29]
内置函数reversed()不会改变列表本身
reversed(myList1)返回一个迭代器，需要用list()函数转换才能显示。

myList1=[21,22,23,24,25,26,27,28,29]
reversed(myList1)
print(reversed(myList1))

1.3.3 列表方法reverse()

myList1=[21,22,23,24,25,26,27,28,29]
myList1.reverse()    #内置函数reversed()与列表方法reverse()的区别：前者不改变列表本身，后者改变列表本身
myList1

[29, 28, 27, 26, 25, 24, 23, 22, 21]
列表方法reverse()改变列表本身

1.4 extend与append的区别

【1】列表的“+”运算

myList1=[21,22,23,24,25,26,27,28,29]
myList2=myList1
myList1+myList2

[21, 22, 23, 24, 25, 26, 27, 28, 29, 21, 22, 23, 24, 25, 26, 27, 28, 29]

myList1=[21,22,23,24,25,26,27,28,29]
myList2=myList1
myList1.extend(myList2)
myList1

[21, 22, 23, 24, 25, 26, 27, 28, 29, 21, 22, 23, 24, 25, 26, 27, 28, 29]
列表的“+”运算相当于列表的方法extend()

【2】列表的方法append()

myList1=[21,22,23,24,25,26,27,28,29]
myList2=myList1
myList1.append(myList2)
myList1

[21, 22, 23, 24, 25, 26, 27, 28, 29, […]]

列表的方法append()与extend()的区别：前者是“以成员身份追加”，而后者是“平等追加”

【3】两个列表的并列相加计算

myList1=[1,2,3,4,5,6,7,8,9]
myList3=[11,12,13,14,15,16,17,18,19]
[i+j for i,j in zip(myList1,myList3)]

[12, 14, 16, 18, 20, 22, 24, 26, 28]

1.5 列表推导式

[2 for i in range(20)]
#先做range()，再做i，最后做2
#注意：①列表推导式必须放在[]中；②for之前是一个表达式

[2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2]

[i for i in range(1,21)]

[1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20]

[i for i in range(1,21,2)]

[1, 3, 5, 7, 9, 11, 13, 15, 17, 19]

range(10)

range(0, 10)

[i for i in range(10)]

[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]

list(range(0,10,2))

[0, 2, 4, 6, 8]

[type(item) for item in [True,"1",1,1.0]]

[bool, str, int, float]

["input/%d.txt"%i+"dd%d"%i for i in range(5)]

[‘input/0.txtdd0’,
‘input/1.txtdd1’,
‘input/2.txtdd2’,
‘input/3.txtdd3’,
‘input/4.txtdd4’]
在Python列表推导式中可以用字符串的占位符，如%d，用法类似C语言的print()、scanf()函数中的占位符
%d为占位符，在对应位置上显示的是“%i”的值

1.6 插入与删除

1.6.1 可以用列表的insert()方法向列表的指定下标处新增或插入分量

lst_1=[10,10,11,12,13,14,15]
lst_1.insert(1,8)   #表示在下标为1的位置插入8
lst_1

[10, 8, 10, 11, 12, 13, 14, 15]

1.6.2 可以用列表的pop()方法删除指定下标的某个元素

lst_1=[10,10,11,12,13,14,15]
lst_1.pop(2)
lst_1

[10, 10, 12, 13, 14, 15]

1.6.3 根据下标来删除某个元素 del

lst_1=[10,10,11,12,13,14,15]
del lst_1[2]
lst_1

[10, 10, 12, 13, 14, 15]

1.6.4 可以用列表的remove()方法删除指定值的某个元素

lst_1=[10,10,11,12,11,13,11,14,15]
for i in lst_1:
    if i==10:
        lst_1.remove(i)
print(lst_1)

[10, 11, 12, 11, 13, 11, 14, 15]
只删除第一个10，第二个10并未删除

lst_1=[10,10,11,12,11,13,11,14,15]
for i in lst_1:
    if i==11:
        lst_1.remove(i)
print(lst_1)

[10, 10, 12, 13, 14, 15]
删除了所有11

debug

lst = [10,11,11,12,11,13,11,14,15]
index = 0
for i in lst:
    print(index)
    if i==11