upper与lower定义
# 写法:字符串.upper()
# 定义:字符串字母改为大写
r = 'are you ok'
print(r.upper())
# 写法:字符串.lower()
# 定义:字符串字母改为小写
e = 'THANK YOU'
print(e.lower())
# 写法:字符串.upper()
# 定义:字符串字母改为大写
r = 'are you ok'
print(r.upper())
# 写法:字符串.lower()
# 定义:字符串字母改为小写
e = 'THANK YOU'
print(e.lower())