这段代码找不到第一个元素

Question

def c(stringenter):
    last = 1
    commandsline = [['a', 'first'], ['b', 'second'], ['c', 'third']]
    for commandblock in commandsline:
        last = last + 1
        if commandblock[0] == stringenter:
            realcommand = str(commandblock[1])
        elif last == len(commandsline):
            realcommand = stringenter
    return realcommand

您好!!!这段代码可以找到并返回第二，第三但是找不到第一个如何解决问题？

Answer 1

索引从0开始，所以你必须改变这样，另一个想法，你应该在最后更新计数器！：

def c(stringenter):
    last = 0
    commandsline = [['a', 'first'], ['b', 'second'], ['c', 'third']]
    for commandblock in commandsline:
        if commandblock[0] == stringenter:
            realcommand = str(commandblock[1])
        elif last == len(commandsline):
            realcommand = stringenter
        last = last + 1
    return realcommand

Answer 2

虽然@ Damian的回答正确回答了您的问题，但您可能会发现其他两种形式的函数更容易：

def c(stringenter):
    commandsline = [['a', 'first'], ['b', 'second'], ['c', 'third']]
    for key, cmd in commandsline:
        if stringenter == key:
            return cmd
    return stringenter

或者直接使用字典：

def c(stringenter):
    commandsline = {'a': 'first', 'b': 'second', 'c': 'third'}
    return commandsline.get(stringenter, stringenter)

Answer 3

您可以尝试这样的事情：

def c(stringenter):
    commandsline = [['a', 'first'], ['b', 'second'], ['c', 'third']]
    for commandblock in commandsline:
        if commandblock[0] == stringenter:
            return commandblock[1]
    return stringenter

如果stringenter等于commandblock [0]中的任何一个它返回commandblock [1]

，它会通过你的命令行列表

如果找不到它。它返回stringenter。