Python中的列表、元组的增、删、改、查

1.列表 list[ ]

列表是python中的基础数据类型之一，其他语言中也有类似于列表的数据类型，比如js中叫数组，他是以[ ] 括起来，每个元素以逗号隔开，而且他里面可以存放各种数据类型比如：li = [‘span’,123,True,(1,2,3,’python’),[1,2,3,’小明’,],{‘name’:’span’}]

列表相比于字符串，不仅可以储存不同的数据类型，而且可以储存大量数据，32位python的限制是 536870912 个元素,64位python的限制是 1152921504606846975 个元素。而且列表是有序的，有索引值，可切片，方便取值。

1.1 列表有序，意味着可以用索引、切片取数据，也可以跳着切片。

li = ["span",[18,188,1888],"python","金融","FX-EXchange"]
l1 = li[2]
l2 = li[1]
print(l1)
print(l2)
l3 = li[0:3]
print(l3)

>>>python 
>>>[18, 188, 1888]
>>>['span', [18, 188, 1888], 'python']

1.2 #增加

list.append() 增加到最后

li = ["span",[18,188,1888],"python","金融","FX-EXchange"]
li.append("Math")
print(li)
>>>['span', [18, 188, 1888], 'python', '金融', 'FX-EXchange', 'Math']

拓展：持续向列表里添加元素，按“Q”退出

while 1:
    username = input(">>>:")
    if username.strip().upper() == "Q":
        break
    else:
        li.append(username)
print(li)

# 插入 list.insert(索引，插入的值)

#添加 list.extend("iterable") 迭代的添加，将添加的值分成可迭代的元素，迭代得添加（分解到最后的可迭代的元素元素）

li = ["span",[18,188,1888],"python","金融","FX-EXchange"]
li.extend("Math")
li.extend([1,2,3])
print(li)
>>>['span', [18, 188, 1888], 'python', '金融', 'FX-EXchange', 'M', 'a', 't', 'h', 1, 2, 3]
PS：int object is not iterable.

1.3

#删除 list.pop(index) 按索引删除

li = ["span",[18,188,1888],"python","金融","FX-EXchange"]
item = li.pop(2)#有返回值，默认是删除最后一个
print(item,li)
>>>python ['span', [18, 188, 1888], '金融', 'FX-EXchange']

#删除 list.remove() 按元素删除

li = ["span",[18,188,1888],"python","金融","FX-EXchange"]
li.remove("span")#无返回值
print(li)
>>>[[18, 188, 1888], 'python', '金融', 'FX-EXchange']

#清空一个列表 list.clear() #清空一个列表，列表仍存在

#删除一个列表 del list

del li
print(li)
>>>NameError: name 'li' is not defined

li = ["span",[18,188,1888],"python","金融","FX-EXchange"]
del li[2:]#切片删除
print(li)
>>>['span', [18, 188, 1888]]

1.4 改动列表里面的值，可直接按索引赋值如：list[index] = “”

还可以切片改：

li = ["span",[18,188,1888],"python","金融","FX-EXchange"]
li[0:2] = "我爱"#iterable value
print(li)
>>>['我', '爱', 'python', '金融', 'FX-EXchange']

li = ["span",[18,188,1888],"python","金融","FX-EXchange"]
li[0:2] = [1,2,3,"我","爱"]
print(li)
>>>[1, 2, 3, '我', '爱', 'python', '金融', 'FX-EXchange']

1.5 查 #可按索引查，也可按切片查也可以通过for循环查找所有的元素

li = ["span",[18,188,1888],"python","金融","FX-EXchange"]
for i in li:
    print(i)
>>>
span
[18, 188, 1888]
python
金融
FX-EXchange

注：公共方法：

列表元素的个数len();元素出现的个数：list.count(value);通过元素找索引 list.index(value)

li = ["span",[18,188,1888],"python","金融","FX-EXchange"]
i = len(li)
num = li.count("spam")
index = li.index("python")#如果查不到会报错
print(i,num,index)
>>> 5 1 2

# 排序

list.sort()#正序排序；

list.sort(reverse=True)#倒序排序

list.reverse()#反转

#####补充：列表的嵌套及其他操作

一、找到列表中的某个元，并显示元素的元素

#补充：列表的嵌套
li = ["span",[18,188,1888],"python","金融","FX-EXchange"]
print(li[3][0])#找到“金融”的金字，并将其打印
>>>金

#找到列表第一个元素，将其首字母大写，并放回
li = ["span",[18,188,1888],"python","金融","FX-EXchange"]
name = li[0].capitalize()
li[0] = name
print(li[0])
>>>Span

#找到‘金融’二字，将‘融’字替换成“元宝”
li = ["span",[18,188,1888],"python","金融","FX-EXchange"]
#li[3] = "金元宝"
#或者
li[3] = li[3].replace("融","元宝")
print(li)
>>>['span', [18, 188, 1888], 'python', '金元宝', 'FX-EXchange']

****元组被称为只读列表，即数据可以被查询，但不能被修改，所以，字符串的切片操作同样适用于元组。***

# tuple

#元组，只读列表，可查询可切片：儿子不能够孙子能改
tu = ("span",[18,188,1888],["python",123,666],"金融","FX-EXchange")
#将1888,改成808
tu[1][2] = 808
print(tu)
>>>('span', [18, 188, 808], ['python', 123, 666], '金融', 'FX-EXchange')

#在列表后面添加9999
tu[1].append(999)
print(tu)
>>>('span', [18, 188,

#列表转换成字符串"".join(iterable)
###列表转换成字符串

li = ["span","金融","FX-EXchange"]
s = "".join(li)
print(s)
>>>span金融FX-EXchange

name = "span"
s = "_".join(name)
print(s)
>>>s_p_a_n

#打印列表中的每一个元素
li = ["span",[18,188,1888],["python",123,666],"金融","FX-EXchange"]
for i in range(len(li)):
    if type(li[i]) == list:
        for j in li[i]:
            print(j,end=" ")
    else: print(li[i],end=" ")
>>>span 18 188 1888 python 123 666 金融 FX-EXchange

###元组里面有一个元素且不加逗号，此元素是什么类型就是什么类型

##
tu1 = (1)
tu2 = (1,)
print(tu1,type(tu1))
print(tu2,type(tu2))
》》》1 <class 'int'>
》》》(1,) <class 'tuple'>