比其他更聪明

Question

我正在尝试(某种程度上)切换命令。

if 'Who' in line.split()[:3]:
    Who(line)   
elif 'Where' in line.split()[:3]:
    Where(line)
elif 'What' in line.split()[:3]:
    What(line)
elif 'When' in line.split()[:3]:
    When(line)
elif 'How' in line.split()[:3]:
    How(line)
elif "Make" in line.split()[:3]:
    Make(line)
elif "Can You" in line.split()[:3]:
    CY(line)
else:
    print("OK")

所以解释。如果Who、What等位于命令的前三个字中，则执行相应的函数。我只想知道是否有比很多if，elif和else更聪明的方法来做这件事

Answer 1

尝试创建一个字典，其中键是命令名，值是实际的命令函数。示例：

def who():
    ...

def where():
    ...

def default_command():
    ...

commands = {
    'who': who,
    'where': where,
    ...
}

# usage
cmd_name = line.split()[:3][0]  # or use all commands in the list
command_function = commands.get(cmd_name, default_command)
command_function()  # execute command

Answer 2

下面是一种不同的方法:使用来自cmd库模块的命令分派：

import cmd

class CommandDispatch(cmd.Cmd):
    prompt = '> '

    def do_who(self, arguments):
        """
        This is the help text for who
        """
        print 'who is called with argument "{}"'.format(arguments)

    def do_quit(self, s):
        """ Quit the command loop """
        return True

if __name__ == '__main__':
    cmd = CommandDispatch()
    cmd.cmdloop('Type help for a list of valid commands')
    print('Bye')

上面的程序将使用提示符'> '启动一个命令循环。它提供了3个命令：help (由cmd.Cmd提供)、who和quit。下面是一个示例交互：

$ python command_dispatch.py 
Type help for a list of valid commands
> help

Documented commands (type help <topic>):
========================================
help  quit  who

> help who

        This is the help text for who

> who am I?
who is called with argument "am I?"
> who
who is called with argument ""
> quit
Bye

备注：

• 命令的docstring也将充当帮助文本。
• cmd.Cmd负责所有的调度细节，所以您可以集中精力实现您的命令
• 如果希望提供一个名为why的命令，则创建一个名为do_why的方法，该命令将可用。
• 有关更多信息，请参阅文档。