startswith就够了

import sys

cmd1_dict = {
    "reset":"reset what",
}
cmd2_dict = {
    "reset board":"board fault",
    "board add":"where to add",
    "board delete":"no board at all",
    "reboot backplane":"impossible",
    "backplane abort":'install first'
}

def run(seq: str):
    seq = seq.split()
    res = "unknown command"
    i = 0
    if len(seq)<1:
        return res
    elif len(seq) == 1:
        for k in cmd1_dict.keys():
            if k.startswith(seq[0]):
                res = cmd1_dict[k]
                i+=1
    elif len(seq) == 2:
        for k in cmd2_dict.keys():
            tmp = k.split()
            if tmp[0].startswith(seq[0]) and tmp[1].startswith(seq[1]):
                res = cmd2_dict[k]
                i+=1
    if i > 1:
        res = "unknown command"
    return res

for cmd in sys.stdin:
    cmd = cmd.strip()
    print(run(cmd))