>>> a='abcdefgh'
>>> a=list(a)
>>> a
['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h']
>>> list(map(str.upper,a))
['A', 'B', 'C', 'D', 'E', 'F', 'G', 'H']
>>> 

1. 對字串中所有字元(僅對字母有效)的大小寫轉換

>>>print ('just to test it'.upper()) #所有字母都轉換成大寫  
>>>JUST TO TEST IT  

>>>print
 
 ('JUST TO TEST IT'.lower() )#所有字母都轉換成小寫  
>>>just to test it  

2. 對字串中的字元(僅對字母有效)部分大小寫轉換:

>>>print ('JUST TO TEST IT'.capitalize()) #字串的首字母轉換成大寫， 其餘轉換成小寫  
>>>Just to test it  

>>>print ('JUST TO TEST IT'.title()) #字串中所有單詞的首字母轉換成大寫， 其餘轉換成小寫  
>>>Just To Test It  
 

3. 判斷字串大小寫函式：

>>>print ('JUST TO TEST IT'.isupper()  )
>>>True 

>>>print ('JUST TO TEST IT'.islower()  )
>>>False 

>>>print ('JUST TO TEST IT'.istitle()  )
>>>False