fastest way to compare strings in python

Question

I'm writing a script in Python that will allow the user to input a string, which will be a command that instructs the script to perform a specific action. For the sake of argument, I'll say my command list is:

lock
read
write
request
log

Now, I want the user to be able to enter the word "log" and it will peform a specific action, which is very simple. However, I would like to match partial words. So, for example, if a user enters "lo", it should match "lock", as it's higher in the list. I've tried using strncmp from libc using ctypes to accomplish this, but have yet to make heads or tails of it.

Answer 1

If you are accepting input from a user, then why are you worried about the speed of comparison? Even the slowest technique will be far faster than the user can perceive. Use the simplest most understandable code you can, and leave efficiency concerns for tight inner loops.

cmds = [
    "lock",
    "read",
    "write",
    "request",
    "log",
    ]

def match_cmd(s):
    matched = [c for c in cmds if c.startswith(s)]
    if matched:
        return matched[0]

Answer 2

This will do what you want:

def select_command(commands, user_input):
    user_input = user_input.strip().lower()
    for command in commands:
        if command.startswith(user_input):
            return command
    return None

However:

You seem overworried about the wrong thing. So 50 users means 50 milliseconds -- you're not going to be run out of town for that kind of "lag". Worry about inefficient database access or problems caused by users typing "r" and getting "read" when they thought they'd get "request". Minimising user keystrokes at the risk of errors is so 1960s that it's not funny. What are they using? ASR33 teletypes? At the very least you could insist on a unique match -- "rea" for read and "req" for request.