Commonly used string operations in python (sample code)

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1. Output repeated strings

print('smile'*6)
#输出6个smile

2. Output partial strings through indexes

print('smile'[1:])
print('smile'[1:3])
#输出
#mile
#mi
#ims

The rules here are the same as the previous list slicing rules.

3. Use in to check the content of the string

a = 'Tomorrow will be a better day. '
print('day' in a)
print('zzz' in a)
#输出
#True
#False

If there is no corresponding string in the string, return False

If there is a corresponding string in the string The corresponding string returns True

4. Format string

a = 'Tomorrow'
b = 'The day after tomorrow'
print('%s will be a better day. '% a)
print('%s will be a better day. '% b)
#输出
#Tomorrow will be a better day. 
#The day after tomorrow will be a better day.

This method allows you to use strings more flexibly, making it easier to modify the sentence content without changing it. Fixed part.

5. String splicing

a = 'aaa'
b = 'bbb'
c = 'ccc'
d = ''.join([a,b,c])
print(d)
d = '*'.join([a,b,c])
print(d)
#输出
#aaabbbccc
#aaa*bbb*ccc

6. A series of built-in methods

st = 'smile puppy'
print(st.count('p'))            #统计元素个数
print(st.capitalize())          #使首字母大写 输出Smile puppy
print(st.center(21,'#'))        #减去st的内容居中，然后两边以符号填充，数目为参数1减去st的内容长度
print(st.startswith('s'))       #判断是否以某个内容开头，返回True或者False
print(st.endswith('y'))         #判断是否以某个内容结尾，返回True或者False
print(st.expandtabs(tabsize=10))#修改\t代表的空格数量
print(st.find('e'))             #查找第一个元素，返回其索引值
# st = 'smile puppy {name}'
# print(st.format(name='puppy'))#格式化的另一种方式，但必须在定义字符串的时候加上{xxx}
print('123abd中午'.isalnum())    #判断字符串中是否都是字母或数字或中文
print('1513'.isdigit())          #判断字符串是否是整形
print('1165162'.isnumeric())     #检测字符串是否只由数字组成
print('31351'.isidentifier())    #判断是否是非法变量
print('anc'.islower())           #判断是否全是小写
print('ABD'.isupper())           #判断是否全是大写
print('ABD'.isspace())           #判断是否全是空格
print('My Name'.istitle())       #判断是否是标题（每个单词首字母是否大写）
print('My Name'.lower())         #全部变小写
print('My Name'.upper())         #全部变大写
print('My Name'.swapcase())      #大写的元素变小写，小写的元素变大写
print('My Name'.ljust(10,'*'))   #内容左边靠，剩下的用“*”填充
print(' My Name\n'.strip())      #清除开头结尾的空格和换行符\n
print('My Name'.replace('Name','Car',1))#将一个“Name”替换为“Car”，最后参数不填默认修改全部
print('My Name'.rfind('e'))      #从右向左检索目标元素，返回其真实的索引值（从左向右）
print('My Name Name'.split(' ',1)) #通过指定分隔符对字符串进行分割，数字参数为分割的次数，不填默认分全割                            #输出['My', 'Name Name']
print('My Name Name'.rsplit(' ',1))#从右开始通过指定分隔符对字符串进行分割
print('My title title'.title())    #返回'标题化'的字符串,即所有单词首字母大写,其余字母小写

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