Scrambling lines from file in Python

Question

I have a file containing large strings, and I need to scramble each and every one of them. This is a portion of my code which does the scrambling.

    for line in filein:
        zzz = line.strip('\n').split()
        yyy = list(zzz)
        random.shuffle(yyy)
        zzzz = ''.join(yyy)
        fout.write(zzzz + '\n')

I found something like this online and so tried to use it here. Except that the original file and the file supposed to containing the scrambled lines... are identical.

But if I say copy one of the lines, and do this in the python interpreter directly...

>>>import random
>>>zzz = "..." ###(one of my large strings would go here, for sake of space didn't put it in)
>>>yyy = list(zzz)
>>>random.shuffle(yyy)
>>>zzzz = ''.join(yyy)
>>>zzzz

the string that gets printed out is a scrambled version of my original string. Am I forgetting to do something really simple and stupid? Or did I miss something important?

Answer 1

line.split returns a list that is only 1 element in length (the line itself) since your data presumably has no whitespace interspersed with it. Then you turn it into a list (which does nothing other than make a shallow copy) so you end up shuffling a list of length 1 -- which leads to a not-so-random result :-).

The fix is to get rid of the split:

for line in filein:
    zzz = line.rstrip('\n')
    yyy = list(zzz)
    random.shuffle(yyy)
    zzzz = ''.join(yyy)
    fout.write(zzzz + '\n')