python字符串不可变数据类型

str1 = 'abcdefg'
print(str1[:]) # abcdefg
print(str1[0:2]) # ab 左闭右开
print(str1[0:2:1]) # ab 默认步长为1
print(str1[:3]) # abc
print(str1[0:]) # abcdefg
print(str1[::-1]) # gfedcba
print(str1[-4:-1]) #def -1代表最右端
# print(str1[-4:-1:-1]) # 尽量避免这样写

str1 = 'my name is fl and my pet is a parrot'
print(str1.find('is')) # 8
print(str1.find('is', 9, 30)) # 25
print(str1.find('dog')) # -1 --find如果没有查找到对应的子串则返回-1
 
print(str1.index('is')) # 8
print(str1.index('is', 9, 30)) # 25
# print(str1.index('dog')) # -1 --index如果没有查找到对应的子串则报错
 
print(str1.rindex('is')) # 25
print(str1.rfind('is')) # 25
 
print(str1.count('is')) # 2
print(str1.count('dog')) # 0
print(str1.count('is', 0, 15)) # 1

str1 = 'Food and Fruit and Animal'
new_str = str1.replace('and', 'he') # Food he Fruit he Animal
new_str = str1.replace('and', 'he', 1) # Food he Fruit and Animal

str1 = 'Food and Fruit and Animal'
new_str = str1.split('and') # ['Food ', ' Fruit ', ' Animal']
new_str = str1.split('and', 1) # ['Food ', ' Fruit and Animal']

mylist = ['I', 'Love', 'You']
new_str = ' '.join(mylist) # I Love You
new_str = '..'.join(mylist) # I..Love..You

str1 = 'oh , my dear , I love you'
new_str = str1.capitalize() # Oh , my dear , i love you
new_str = str1.title() # Oh , My Dear , I Love You
new_str = str1.upper() # OH , MY DEAR , I LOVE YOU
new_str = str1.lower() # oh , my dear , i love you

str1 = "   come on baby , it's true  "
new_str = str1.lstrip() # come on baby , it's true
new_str = str1.rstrip() #    come on baby , it's true
new_str = str1.strip() # come on baby , it's true

str1 = 'abcd'
new_str = str1.ljust(10, '.') # abcd......
new_str = str1.ljust(10) # abcd(后面有六个空格)
new_str = str1.rjust(10, '/') # //abcd
new_str = str1.center(10, '.') # ...abcd...

str1 = 'hello world'
print(str1.startswith('he')) # True
print(str1.startswith('ho')) # False
print(str1.endswith('ho')) # False
print(str1.endswith('world')) # True

str1 = 'hello world'
print(str1.isalpha()) # False
str1 = 'abc'
print(str1.isalpha()) # True
 
str2 = '123 45'
print(str2.isdigit()) # False
str2 = '123'
print(str2.isdigit()) # True
 
str3 = 'abc123'
print(str3.isalnum()) # True
str3 = 'abc 123'
print(str3.isalnum()) # False
 
str4 = '123 '
print(str4.isspace()) # False
str4 = '   '
print(str4.isspace()) # True