How do I catch a particular exception that I am expecting?

Question

I have been trying to make a simple zip file password cracker (just for fun, not malicious purposes) however my try and except statement will not work. No matter the input it always leads to the except statement, and the else is never executed (even though the zip file does extract)

import zipfile

k = 0
file = zipfile.ZipFile('john.zip')
def check(i):
    p = bytes(i, 'ascii')
    try:
        file.extractall(pwd=p)
    except:
        return False
    else:
        return True

def crack():
        x = open('john(1).txt', 'r')
        for i in x.readlines():
            i.strip('\n')
            k = check(i)
            if k == True:
                print('Password is: ' + k)
                break;
            x.close()
        x.close()`

Have you tried taking that statement out of the `try` block so you can actually see the error? — TigerhawkT3, Jul 21 '15 at 00:46
Yes, i have ran the code by itself and you get the error you would expect, and no error when the correct password is inputed — Ellis, Jul 21 '15 at 00:49
Have you tried catching only Exception `except Exception:` instead of just `except:` ? — johnharris85, Jul 21 '15 at 01:18
Better yet, just catch the exception you would expect from a bad password. — martineau, Jul 21 '15 at 01:21

score 1 · Accepted Answer · answered Jul 21 '15 at 01:50

1

1) Log the error in the except block. Helps a lot.

2) You are closing the file in the 'for' loop. Bad idea as the loop reads lines from the file.

3) The last line has a reverse quote character at the end (may be a typo in the question): `

answered Jul 21 '15 at 01:50

ChrisC73

1,833
14
14

score 0 · Answer 2 · edited Jul 21 '15 at 02:02

I got it working with a couple of changes in crack() as shown in comments below. Here is what worked for me:

…
def crack():
    x = open('john(1).txt', 'r')
    for i in x.readlines():
        i = i.strip() # not just the statement i.strip('\n')
        k = check(i)
        if k == True:
            print('Password is: ' + i) # not print('Password is: ' + k)
…

How do I catch a particular exception that I am expecting?

2 Answers2