通过字典推导式，颠倒字典的键名和值:将{‘py‘: “python09“, ‘java‘: “java09“} 转换为： {‘python09‘: “py“, ‘java09‘: “java“}

"""
3、通过字典推导式，颠倒字典的键名和值:将{'py': "python09", 'java': "java09"} 转换为： {'python09': "py", 'java09': "java"}
"""
old_dict = {'py': "python09", 'java': "java09"}
# 方法一：
new_dict = {old_dict[item]: item for item in old_dict}
print(new_dict)
# 方法二：
dic = {v: k for k, v in old_dict.items()}
print(dic)