python字符串操作的15种方法汇总

str = '这是一句话'
print( str )

str = "What's your name?"
print( str )

str ='''
这是一个多行文本. 这是第一行.这是第二行.
"你的名字是," 我问到。他会答"我的名字是木木"
'''
print(str)

str1 = 'What\'s your name?'
str2 = "What's your name?"
print(str1)
print(str2)

s = 'ABCDEFGHIJKLMN'
s1 = s[0]
print('s[0] = ' + s1)   #s[0] = A
print('s[3] = '+ s[3])  #s[3] = D
print('倒数第三个数为：' + s[-3])   #倒数第三个数为：L
print('最后一个数为：' + s[-1])     #最后一个数为：N

s = 'ABCDEFGHIJKLMN'
s2 = s[0:3]
print('s[0:3] = ' + s2)     
#s[0:3] = ABC
​
print('整个字符串如下：' + s[:])    
#整个字符串如下：ABCDEFGHIJKLMN
​
print('整个字符串如下：' + s[0:])   
#整个字符串如下：ABCDEFGHIJKLMN
​
print('前两个字符：' + s[:2])      
 #前两个字符：AB

s3 = 'ABCDEFGHIJKLMN'
print(s3[0:6:2])    #ACE
print(s3[::2])      #ACEGIKM
print(s3[4:0:-1])   #倒着取:EDCB
print(s3[3::-1])    #DCBA
print(s3[-1::-1])   #NMLKJIHGFEDCBA

s = 'alexWUsir'
s4_1 = s.capitalize()  #首字母大写
print(s4_1)   #Alexwusir

s = 'alexWUsir'
s4_2 = s.upper() #全部大写
print(s4_2)   #ALEXWUSIR

s = 'alexWUsir'
s4_3 = s.lower() #全部小写
print(s4_3)   #alexwusir

s = 'alexWUsir'
s4_4 = s.swapcase() #大小写互换
print(s4_4)   #ALEXwuSIR

#center(self, width, fillchar=None)s = 'alexWUsir'
s5_1 = s.center(20,'%')  #用%填充
s5_2 = s.center(15,'*')  #用*填充
s5_3 = s.center(20)      #空白填充
print(s5_1)     #%%%%%alexWUsir%%%%%%
print(s5_2) 
  #***alexWUsir***
print(s5_3)   #     alexWUsir

s = 'xc——gx*zs_shy+hihn9bbklv yiu'
s7 = s.title()
print(s7)  
#Xc——Gx*Zs_Shy+Hihn9Bbklv Yiu

print('------------验证码的检验问题(先转化为全部大写，再核对) --------------')
s_str = 'aBcD1s'
you_input = input('请输入验证码，不区分大小写')
while s_str.upper()!= you_input.upper():
    print('验证码错误')
    you_input = input('请重新输入')
print('输入成功')

s = 'alexWUsir'
s8_11 = s.find('W')
s8_12 = s.index('W')
s8_21 = s.find('WU')
s8_22 = s.index('WU')
s8_31 = s.find('A')
s8_32 = s.index('A')
print(s8_11,type(s8_12))     
 #4 <class 'int'>
​
print(s8_21 ,type(s8_22))    
 #4 <class 'int'>
​
print(s8_31 ,type(s8_32))     
#报错：ValueError: substring not found----未找到子字符串

print('----------------检验非法（敏感）字符-------------------')
s = 'gcu木木gckhb'
if '木木' in s:
    print('您的评论有敏感字符')

s = '  alexW%Usir  %2%  '
s9_1 = s.strip()   
#删除字符串前后的空格
​
print(s9_1)   
#alexW%Usir  %2%
​
ss = '% alexW%Usir  %2%  %'
s9_2 = ss.strip('%')   
#删除字符串前后的%
​
print(s9_2)  
# alexW%Usir  %2%　　

username = input('请输入名字：').strip()
if username == '小明':
    print('你好呀 主人')

s = 'alexaa wusirl'
s10 = s.count('a')
print('此字符串中有' + s10 + '个a')   
#报错：TypeError: must be str, not int
​
print('此字符串中有' + str(s10) + '个a')    
#此字符串中有3个a

s = 'alex wusir taibai'
s1 = 'ale:x wus:ir :taibai'
s11_1 = s.split()
print(s11_1)    #['alex', 'wusir', 'taibai']
s11_2 = s1.split(':')
​
print(s11_2)   #['ale', 'x wus', 'ir ', 'taibai']

s12_1 = '我叫{},今年{}岁，爱好{},再说一下我叫{}'.format('小明',18,'学习','小明')
print(s12_1)  

s12_2 = '我叫{0},今年{1}岁，爱好{2},再说一下我叫{0}'.format('小明',18,'学习')

print(s12_2)​

s12_3 = s1 = '我叫{name},今年{age}岁，爱好{hobby},再说一下我叫{name}'.format(name = '小明',age = 18,hobby = '学习')

print(s12_3)

s13_1 = '小明，哈喽你好，我是小明'
s13_2 = s13_1.replace('小明','张三')
s13_3 = s13_1.replace('小明','张三',1)
​
print(s13_1)

print(s13_2)

print(s13_3)

s14 = ''print(s14.isdigit())   #是否由数字组成
print(s14.isalpha())   #是否由字母组成
print(s14.isalnum())   #是否由字母或数字组成
s14_1 = 'zxcs'
s14_2 = '123546'
s14_3 = 'c1d21c4'
print('----------s14_1----------')
print(s14_1.isdigit())   #False
print(s14_1.isalpha())   #True
print(s14_1.isalnum())   #True
print('----------s14_2----------')
print(s14_2.isdigit())  #True
print(s14_2.isalpha())   #False
print(s14_2.isalnum())   #True
print('----------s14_3----------')
print(s14_3.isdigit())   #False
print(s14_3.isalpha())   #False
print(s14_3.isalnum())   #True

s14_4 = ' n  '
s14_5 = ''
s14_6 = '   '
print(s14_4.isspace())  #False：有除空格外的其他字符
print(s14_5.isspace())  #False：空
print(s14_6.isspace())  #True：全是空格

s = 'xiaoming'
for i in s:
    print(i)

#举例：

s = 'fhdsklfds'
if 'sk' in s:
    print('非法')
print('------------------------')
if 'skk' not in s:
    print('合法')