favorite_digit = {
    'john' : 4, 
    'Tom' : 5, 
    'Lisa' : 9, 
    'liu' : 5, 
    'alice' : 0, 
    }
for name in sorted(favorite_digit.keys()):
  print(name.title())

for name in sorted(favorite_digit.keys()):
  print(name)

favorite_digit_lower = {}  #先创建一个字典将原先字典键小写化储存

for name, digit in favorite_digit.items():
  name = name.lower() #然后遍历原先的字典，将键转化为小写，同时将数据储存在新的字典中
  #print(name) #这里也可以加一个print检查name是否成功写入小写
  favorite_digit_lower [name] = digit #将原来字典的内容复制到新字典里
for name in sorted(favorite_digit_lower.keys()):
  print(name.title()) #再次打印，结果为预期结果