trying to write a list of all possible 4 characters combinations in Python

Question

basically i want all 4 characters combinations possible written in a txt file The problem is duplication should be allowed , i want the combinations 1111,2222... Where do you think i went wrong and how would you fix it?

import itertools
import sys
import os

tester = open(r"available.txt","a")
lol =[]
a = [1,2,3,4,5,6,7,8,9,0,'_','.','a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z']

lol=list(itertools.combinations(a, 4))
for comb in lol:
    tester.write(str(comb)+"\n")

'available.txt' now has a size of 2.7GB This is killing my laptop — finnmglas, May 12 '20 at 13:11
You are assigning the list of 2 million items 2 million times. — Klaus D., May 12 '20 at 13:12
Try to reproduce your question. Your data is too big. It takes a long time to process the loop. — Dejene T., May 12 '20 at 13:18
consider https://stackoverflow.com/a/14006967/1766544 or in python documtation https://docs.python.org/2/library/itertools.html#itertools.product — Kenny Ostrom, May 12 '20 at 14:42

Eric Jin · Answer 1 · 2020-05-12T13:27:54.863

With combinations with replacement - 101270 entries: (runs instantly excluding file IO)

import itertools
with open('available.txt', 'w') as f:
    lol = []
    a = [i for i in '1234567890._abcdefghijklmnopqrstuvwxyz']
    lol = list(itertools.combinations_with_replacement(a, 4))
    for comb in lol:
        f.write(comb)

With combinations without replacement - 73815 entries: (runs instantly excluding file IO)

import itertools
with open('available.txt', 'w') as f:
    lol = []
    a = [i for i in '1234567890._abcdefghijklmnopqrstuvwxyz']
    lol = list(itertools.combinations(a, 4))
    for comb in lol:
        f.write(comb)

With permutations without replacement - 1771560 entries: (runs instantly excluding file IO)

import itertools
with open('available.txt', 'w') as f:
    lol = []
    a = [i for i in '1234567890._abcdefghijklmnopqrstuvwxyz']
    lol = list(itertools.permutations(a, 4))
    for comb in lol:
        f.write(comb)

With permutations with replacement - 2085136 entries: (runs in about 2 seconds excluding file IO)

lol = []
for a in '1234567890._abcdefghijklmnopqrstuvwxyz':
    for b in '1234567890._abcdefghijklmnopqrstuvwxyz':
        for c in '1234567890._abcdefghijklmnopqrstuvwxyz':
            for d in '1234567890._abcdefghijklmnopqrstuvwxyz':
                lol.append(a+b+c+d)
with open('my_dump.txt', 'w') as f:
    f.write(repr(lol))

Most likely you wanted permutations with replacement, as you specified 38^4 total possibilities. (Use the term permutations next time!) Slicing off the first 100 entries in this list:

>>> lol[:100]
['1111', '1112', '1113', '1114', '1115', '1116', '1117', '1118', '1119', '1110', '111.', '111_', '111a', '111b', '111c', '111d', '111e', '111f', '111g', '111h', '111i', '111j', '111k', '111l', '111m', '111n', '111o', '111p', '111q', '111r', '111s', '111t', '111u', '111v', '111w', '111x', '111y', '111z', '1121', '1122', '1123', '1124', '1125', '1126', '1127', '1128', '1129', '1120', '112.', '112_', '112a', '112b', '112c', '112d', '112e', '112f', '112g', '112h', '112i', '112j', '112k', '112l', '112m', '112n', '112o', '112p', '112q', '112r', '112s', '112t', '112u', '112v', '112w', '112x', '112y', '112z', '1131', '1132', '1133', '1134', '1135', '1136', '1137', '1138', '1139', '1130', '113.', '113_', '113a', '113b', '113c', '113d', '113e', '113f', '113g', '113h', '113i', '113j', '113k', '113l']

alphabet = list(string.digits + '_.' + string.ascii_lowercase) — Kenny Ostrom, May 12 '20 at 14:40

finnmglas · Answer 2 · 2020-05-12T13:29:37.683

1

Running this almost fried my laptop.

A few improvements for the code:

Do not use tester.write(comb), as you can't write a tuple to a file. Only strings (str). So I decided use tester.write(str(comb)).
You should probably find a better way of doing whatever you want to do, because a way that creates files of this size and almost kills a laptop is probably not the most efficient way ^^

Improved Code:

#! /usr/bin/python3

import itertools
import sys
import os

tester = open(r"available.txt","a")
lol =[]
a = ['1','2','3','4','5','6','7','8','9','0','_','.','a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z']

lol=list(itertools.combinations(a, 4))

for comb in lol:
    tester.write(str(comb))

edited May 12 '20 at 13:29

answered May 12 '20 at 13:22

finnmglas

1,626
4
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Why are you writing 2 million instances of a list with 2 million entries? When I first tested it it took up 2.7GB and almost crashed me – Eric Jin May 12 '20 at 13:25
@EricJin Yeah it did crash me too ... That loop was in the code he initially uploaded, I copied it and just noticed that it was stupid. Thanks! – finnmglas May 12 '20 at 13:31

trying to write a list of all possible 4 characters combinations in Python

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