一、字符串中的大小写字母转换
(1)S.lower():将字符串S中的大写字母转换为小写字母,数字不变
(2)S.upper():将字符串S中的小写字母转换为大写字母,数字不变
二、字符串中特定位置字符的替换
(1)S.replace(A,B,N):将字符串S中第N个A替换为B,并返回新的字符串,如N=0,则全部替换
注意:字符串S本身并不改变
print("This is nice. Yes!".lower())
print("So is this? Sure!!".upper())
print("This is nice. Really nice.".replace("nice", "sweet"))
print("This is nice. Really nice.".replace("nice", "sweet", 1)) # count = 1
print("----------------")
s = "This is so so fun!"
t = s.replace("so ", "")
print(t)
print(s) # note that s is unmodified (strings are immutable!)