python的字符串操作

>>> s="how are you"   #定义字符串
>>> s
'how are you'
>>> s.capitalize()   #首字母大写
'How are you'
>>> s.upper()         #全部大写
'HOW ARE YOU'
>>> s
'how are you'
>>> s.swapcase()  #大小写交换
'HOW ARE YOU'
>>> s=s.upper()
>>> s
'HOW ARE YOU'
>>> s.lower()  #全部小写
'how are you'
>>> s
'HOW ARE YOU'
>>> len(s)   #字符串长度
11

>>> "abdcd1231".isalnum() #检测字符串是否由0-9A-Za-z构成
True
>>> "abd 123".isalnum() #中间有空格，所以结果为False
False