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Learn Python characters and lists simply (detailed examples)
- WBOYforward
- 2022-05-25 13:49:162849browse
This article brings you relevant knowledge about python, which mainly introduces issues related to characters and lists, including string input and output, list loop traversal, and list addition. Let’s take a look at deletion, modification, nesting of lists, etc. I hope it will be helpful to everyone.
Recommended learning: python video tutorial
1. String
String representation
a = "100"b = "hello world"c = 'hello world'd = '100'e = ‘18.20520'
1.1The len function returns the length or number of objects
Python len() method returns the length or number of items of an object (character, list, tuple, dictionary, etc.).
In [1]: a="abcdefg"In [2]: len(a)Out[2]: 7In [3]: b = [1,2,3,4,5,66,77,8888]In [4]: len(b)Out[4]: 8
1.2 Another way to form a string:
Strings will be spliced and numbers will be added
In [5]: a ="lao"In [6]: b="wang"In [7]: c=a+b In [8]: c Out[8]: 'laowang'In [9]: d= "===="+a+b+"===="In [10]: d Out[10]: '====laowang===='In [11]: f="===%s===="%(a+b)In [12]: f Out[12]: '===laowang===='
2. String Input and output
2.1 String input
Input information
name = input(“ 请输入你的姓名:”)position = input(“ 请输入你的职业:”)address = input(“ 请输入你的地址:”)
Output information
print("="*50)print(" 姓名:%s\n 职业:%s\n 地址:%s" % (name,position,address))print("="*50)
2.2Format usage syntax :
Display data in a formatted manner, and can display data in a variety of ways. Such as through position, through keyword parameters, through mapping list.
1. By position
print("my name is {0},age is {1}".format('Liu Bei',20))
print("my name is {},age is {}".format('Liu Bei',20))
print("{1},{0},{1}".format('Liu Bei',20))
2. Through keyword parameters
print(“{age},{name}”.format(age=28,name=“Cao Cao”))
print(“{name},{name},{age }".format(age=28, name="Cao Cao"))
3. Through mapping list
alist = ["Sun Quan", 20, "China"]
blist = ["Diao Chan", 18,"China"]
print("my name is {1[0]}, from {0[2]}, age is {0[1]}".format(alist,blist))
The data obtained by input in python3 is saved in the form of a string. Even if the input is a number, it is saved in the form of a string.
# Determine whether the password is correct
user_name = input(“ 请输入用户名:”)password = input(“ 请输入密码:”)if user_name == “beijing” and password == “123” :print(“ 欢迎登录北京官网!")else :print(" 你的账户或者密码错误!")
2.3 Subscript introduction
Subscript index index
The so-called "subscript" is the number, just like the storage cabinet in the supermarket Number, through which the corresponding storage space can be found.
Get some characters through subscripts
If there is a string: name = 'abcdef', the actual storage in the memory is as follows: 
In [1] : len(name)
Out[1]: 7
In [2]: name[len(name)-1]
Out[2]: 'g'
In [3]: name[-1]
Out[3]: 'g' Positive numbers go from left to right, negative numbers go from right to left
2.4 Slice
Slicing refers to the operation of intercepting a part of the operation object. Strings, lists, and tuples all support slicing operations.
Syntax of slicing: [Start: End: Step]
Note: The selected interval is left-closed and right-open, that is, it starts from the "start" bit and ends at the previous bit of the "end" bit. (Does not include the end bit itself). Note that if the step size is not written, the default is 1.
The step size controls the direction. Positive numbers are taken from left to right, and negative numbers are taken from right to left.
In [1]: name="abcdefABCDEF"In [2]: name[0:3]Out[2]: 'abc'In [3]: name[0:5:2]Out[3]: 'ace'In [4]: name[-1::-1] #逆序(倒叙)Out[4]: 'FEDCBAfedcba'
Summary of subscripts and slicing
[:] Extract the entire string from the beginning (default position 0) to the end
[start:] Extract from the start to the end
[:end] Extract from the beginning to the end - 1
[start:end] Extract from start to end - 1
[startstep] Extract from start to end - 1, extract one character per step
[::-1] Reverse order
3. Common string functions
find(), rfind (), index (), rindex (), replace (), split (), parttion (), rparttion (), splitlines () , startswith (), endswith (), lower (), upper (),…………
3.1find and rfind
In [1]: mystr="hello world yanzilu and yanziluPython"In [2]: mystr
Out[2]: 'hello world yanzilu and yanziluPython
In [3]: mystr.find("and")Out[3]: 20In [4]: mystr.find("world") #存在则返回该单词开始的下标Out[4]: 6In [5]: mystr.find("world1") #不存在则返回-1Out[5]: -1In [6]: mystr.find("yanzilu")Out[6]: 12In [7]: mystr.find("yanzilu",20,len(mystr)) #指定查找区域Out[7]: 24In [8]: mystr.rfind("yanzilu") #rfind，从右往左搜索Out[8]: 24
3.2index, rindex
has the same function as find, with one difference. If the content cannot be searched by index, an error will be reported
In [9]: mystr.index("and") Out[9]: 20In [10]: mystr.index("yanzilu")Out[10]: 12In [11]: mystr.index("yanzilu",20,len(mystr)) #指定查找区域Out[11]: 24In [12]: mystr.rindex("yanzilu") #从右往左搜索Out[12]: 24In [13]: mystr.rindex("zhangsan") #搜索不存在的会报错---------------------------------------------------------------------------ValueError Traceback (most recent call last)<ipython-input-67-6aff7ee60ad5> in <module>----> 1 mystr.rindex("zhangsan")ValueError: substring not found</module></ipython-input-67-6aff7ee60ad5>
3.3 replace Replace
In [14]: mystr
Out[14]: 'hello world yanzilu and yanziluPython'In [15]: mystr.replace("world","WORLD")Out[15]: 'hello WORLD yanzilu and yanziluPython'In [16]: mystr
Out[16]: 'hello world yanzilu and yanziluPython'In [17]: mystr.replace("yan","zhang")Out[17]: 'hello world zhangzilu and zhangziluPython'In [18]: mystr.replace("yan","zhang",1) #指定替换次数Out[18]: 'hello world zhangzilu and yanziluPython'In [19]: mystr.replace("yan","xxx",1)Out19]: 'hello world xxxzilu and yanziluPython'In [20]: mystr.replace("yan","xxx",2)Out[20]: 'hello world xxxzilu and xxxziluPython'In [21]: mystr.replace("yan","xxx",33) #替换次数可以超过最大值Out[21]: 'hello world xxxzilu and xxxziluPython'
3.4split, function to split, cut, syntax: split(str=' ',maxsplit)
In [22]: mystr
Out[22]: 'hello world yanzilu and yanziluPython'In [23]: mystr.split(" ")Out[23]: ['hello', 'world', 'yanzilu', 'and', 'yanziluPython']In [24]: mystr.split("and")Out[24]: ['hello world yanzilu ', ' yanziluPython']In [25]: mystr.split(" ",3)Out[25]: ['hello', 'world', 'yanzilu', 'and yanziluPython']In [26]: mystr.split()Out[26]: ['hello', 'world', 'yanzilu', 'and', 'yanziluPython']
3.5 partition, split mystr into three parts with str, before str , str itself, after str
In [27]: mystr
Out[27]: 'hello world yanzilu and yanziluPython'In [28]: mystr.partition("and")Out[28]: ('hello world yanzilu ', 'and', ' yanziluPython')In [29]: mystr.partition("yanzilu")Out[29]: ('hello world ', 'yanzilu', ' and yanziluPython')In [30]: mystr.rpartition("yanzilu")Out[30]: ('hello world yanzilu and ', 'yanzilu', 'Python')
3.6splitlines function, split according to rows, return a list containing each row as an element
In [31]: mystr1 Out[31]: 'hello\nworld\nyanzilu\nand\nyanziluPython'In [32]: mystr1.splitlines()Out[32]: ['hello', 'world', 'yanzilu', 'and', 'yanziluPython']
3.7 startswith () determines whether it begins with str; endswith () determines whether it ends with str.
In [33]: mystr
Out[33]: 'hello world yanzilu and yanziluPython'In [34]: mystr.startswith("hello")Out[34]: TrueIn [35]: mystr.startswith("Hello")Out[35]: FalseIn [36]: mystr.startswith("h")Out[36]: TrueIn [37]: mystr.endswith("Pthon")Out[37]: FalseIn [38]: mystr.endswith("Python")Out[38]: True
3.8upper converts all letters to uppercase; lower converts all letters to lowercase.
In [39]: mystr.upper()。 Out[39]: 'HELLO WORLD YANZILU AND YANZILUPYTHON'In [40]: mystr.lower() Out[40]: 'hello world yanzilu and yanzilupython'
3.9center adds spaces on both sides of the string and displays it in the center
In [41]: mystr = "那一夜我伤害了你"In [42]: mystr = mystr.center(30) In [43]: mystr Out[43]: ' 那一夜我伤害了你3.10 lstrip deletes the spaces on the left side of the string###
In [44]: mystr.lstrip()Out[44]: '那一夜我伤害了你
3.11rstrip删除字符串右边的空格
In [45]: mystr.rstrip()Out[45]: ' 那一夜我伤害了你'
3.12 strip删除字符串两边的空格
In [46]: mystr.strip()Out[46]: '那一夜我伤害了你'
3.13isspace判断是否只包含空格
In [47]: mystr.isspace()Out[47]: FalseIn [48]: mystr = " "In [49]: mystr.isspace()Out[49]: True
3.14salpha判断字符串中是否只包含字母
In [50]: mystr = "abc" In [51]: mystr.isalpha()Out[51]: TrueIn [52]: mystr = "abc1"In [53]: mystr.isalpha()Out[53]: False
3.15isdigit判断是否只包含数字。
In [54]: mystr = "123123"In [55]: mystr.isdigit()Out[55]: TrueIn [56]: mystr = "123123aa"In [57]: mystr.isdigit()Out[57]: False
3.16isalnum判断是否只包含数字和字母。
In [58]: mystr.isalnum()Out[58]: TrueIn [59]: mystr = "123123 aa"In [60]: mystr.isalnum()Out[60]: False
3.17title将每个单词的首字母大写，其余小写
In [61]: mystr = 'hello world yanzilu and yanziluPython'In [62]: mystr.title()Out[63]: 'Hello World Yanzilu And Yanzilupython'
3.18capitalize将字符串的第一个字符大写，其余小写
In [64]: mystr.capitalize()Out[64]: 'Hello world yanzilu and yanzilupython'
3.19count统计单词出现的次数
In [65]: mystr.count("hello")Out[65]: 1In [66]: mystr.count("yan")Out[66]: 2
3.20join在每个字符后面插入str，构造出一个新的字符串。
In [67]: mystr = " "In [68]: name Out[68]: ['hello', 'world', 'yanzilu', 'and', 'yanziluPython']In [69]: mystr.join(name)Out[69]: 'hello world yanzilu and yanziluPython'In [70]: mystr = "_"In [71]: mystr.join(name)Out[71]: 'hello_world_yanzilu_and_yanziluPython'
4.列表及循环遍历
4.1列表的格式
#变量names_list的类型为列表names_list = [' 刘备',' 曹操',' 孙权']
#打印多个姓名names_list = [' 刘备',' 曹操',' 孙权']print(names_list[0])print(names_list[1])print(names_list[2]) names = [' 刘备',' 曹操',' 孙权'] for x in names print(x)i=1while i<len><h2>5.列表的增删改查：</h2>
<p>列表中存放的数据是可以进行修改的，比如"增"、“删”、“改”</p>
<h3><strong>5.1列表的添加元素("增"append, extend, insert)</strong></h3>
<p>append可以向列表添加元素<br> extend将另一个集合中的元素逐一添加到列表中<br> insert在指定位置index前插入元素</p>
<pre class="brush:php;toolbar:false">name=[“刘备” , ”曹操” , ”孙权”]print(“增加之前：”,name)info=[“黄忠” , ”魏延”]
append追加
names.append("吕布")names.append("貂蝉")names.append(info)
#append把中括号也增加上了print("增加之后：",names)
这里是引用
使用extend合并列表
info = ["黄忠","魏延"]names.extend(info)print("增加之后：",names)
这里是引用
insert在指定位置前插入元素
names.insert(0,"刘禅")print("增加之后：",names)
5.2删除元素 (" 删 "del, pop, remove)
del根据下标进行删除
pop删除最后一个元素
remove根据元素的值进行删除
names = ['刘备', '曹操', '孙权', '吕布', '貂蝉', '黄忠', '魏延']print("删除前：",names)
5.3del指定下标删除
del names[1]print("del删除后：",names)
5.4使用pop删除最后一个元素
names.pop()names.pop()print("pop删除后：",names)
5.5使用remove根据元素值进行删除
name = input("请输入您要删除的历史人物：")names.remove(name)print("remove删除后：",names)
5.6列表的修改
通过下标修改元素 (" 改 ")
names = ["刘备","曹操","孙权"]names[0] = "刘禅"print(names)
5.7查找元素("查"in, not in, index, count)
python中查找的常用方法为：
in （存在）, 如果存在那么结果为True ，否则为False
not in （不存在），如果不存在那么结果为True ，否则False
index和count与字符串中的用法相同
names = ['刘备', '曹操', '孙权', '吕布', '貂蝉', '黄忠', '魏延',"曹操"]findName = input("请输入您要查找的姓名：")if findName in names:
print("已经找到：%s"%findName)else:
print("没有找到：%s"%findName)
In [1]: names = ['刘备', '曹操', '孙权', '吕布', '貂蝉', '黄忠', '魏延',’曹操’]In [2]: name.index(“曹操”)Out[2]:1In [3]: name.index(“曹操”,2,leb(names))Out[3]:7In [4]: name.count(“曹操”)Out[4]:2
6.排序(sort, reverse)
sort方法是将list按特定顺序重新排列，默认为由小到大（True：从小到大；False从大到小）
reverse=True可改为倒序，由大到小。
reverse方法是将list逆置。需要先排序再降序
7.列表嵌套
类似while循环的嵌套，列表也是支持嵌套的一个列表中的元素又是一个列表，那么这就是列表的嵌套
示例：
school_names = [[' 北京大学',' 清华大学'],[' 南开大学',' 天津大学'],[' 贵州大学',' 青海大学']]print(school_names)
#print(school_names)#print(len(school_names))#print(school_names[2][1])for school in school_names:
print("="*30)
print(school)
for name in school:
print(name)
8.列表嵌套的应用- - 随机安排老师工位
一个学校，有3个办公室，现在有8位老师等待工位的分配，请编写程序，完成随机的分配
import random
offices = [[ ],[ ],[ ]]names = ['刘备', '曹操', '孙权', '吕布', '貂蝉', '黄忠', '魏延','大乔']for office in offices:
#得到一个教师的下标
index = random.randint(0,len(names)-1)
#分配老师
name = names[index]
office.append(name)
#要移除已经完成分配的老师
names.remove(name)for name in names:
#得到办公室编号
index = random.randint(0,2)
offices[index].append(name)#print(offices)#打印出来哪些办公室有哪些老师i= 1for office in offices:
#office = ["刘备","曹操"]
print("办公室%s ： 共%s人"%(i,len(office)))
i+=1
for name in office:
print("%s"%name,end="\t\t")
print()
print("="*30)
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