通过两个例子学习if else判断

1.if——else

# ifelse 判断_username = 'dmr'_password = '123'if username == _username and password == _password:    print('welcome user {name} login ....'.format(name=username))else:    print('invalid username and password!')

2.if——elif——else

# elifage_of_oldboy = 56guess_age = int(input('guessage;'))if guess_age == age_of_oldboy:    print('yes, you get it')    elif guess_age