Why is my Python Dictionary only returning the last value?

Question

I have an rfid reader which when scanned returns a UID as "backData"

I have my users (username and UID) stored in a text file.

I've managed to read the text file into a python dictionary, but when i scan my card, it is only accepting the last UID in the text file.

Text File:

164 168 124 90 42, user1
114 156 203 196 225, user2

Python Code:

for line in uid_file:
    info = line.split(",")
    key = info[0]
    uname = info[1]
    c = len(uname)-1
    uname = uname[0:c]
    uid_dict[key] = uname
    USER = [int(i) for i in key.split()]

    if backData == USER:
        f = open("/mnt/lock_logs/lock_log.csv", "a");
        print f
        value = ('\n') + uname
        myString = str(value)
        f.write(myString)
        f.close()
     else:
        print "Access Denied"

So if I scan the card assigned to user2, it works, but if I scan the card assigned to user1, I get Access Denied.

If i print the variable USER, it returns both UIDs from the text file. Any ideas on what I need to change??

Answer 1

I think this is because you continue to evaluate your for loop even after the user 1 is matched. Add a 'break' to the bottom of your if statement.

if backData == USER:
    f = open("/mnt/lock_logs/lock_log.csv", "a");
    print f
    value = ('\n') + uname
    myString = str(value)
    f.write(myString)
    f.close()
    break

I recreated your file and am able to get predicted behavior with the following code. Not that I hard coded backData and have tried it with both USER lists with success.

filename = 'uid.txt'

with open(filename) as uid_file:
    uid_dict={}

    backData = [164, 168, 124, 90, 42]
    no_matches = True

    for line in uid_file:
        info = line.split(",")
        key = info[0]
        uname = info[1]
        print info[0], info[1]
        c = len(uname)-1
        uname = uname[0:c]
        uid_dict[key] = uname
        USER = [int(i) for i in key.split()]

        if backData == USER:
            print "user matches"
            no_matches = False          
            break

    if no_matches:
        print "Access Denied"