I would like to execute a named function on a python object by variable name. For example, let’s say I’m reading in input that looks something like this:

enqueue 1
enqueue 12
enqueue 5
enqueue 9
sort
reverse
dequeue
print

Afterwards, we should see:

[9,5,1]

Let’s say we need to implement a data structure that consumes this input. Fortunately, all of this behavior already exists within the built-in list datatype. What we can do is extend the built-in list to map the appropriate methods, like so:

class qlist(list):
    def enqueue(self, v):
        self.insert(0,v)

    def dequeue(self):
        return self.pop()

    def print(self):
        print(self)

The sort and reverse methods are already built-in to list, so we don’t need to map them. Now, we simply need a driver program that reads and processes commands to our new qlist class. Rather than map out the different commands in if/else blocks, or use eval(), we can simply use getattr, for example:

if __name__ == '__main__':
    thelist = qlist()
    while line in sys.stdin:
        cmd = line.split()
        params = (int(x) for x in cmd[1:])
        getattr(thelist, cmd[0])(*params)