what's wrong with the program?

Question

I wanted to make a program to shuffle a list of alphabets and store shuffled list in an another list such that no two lists are shuffled exactly the same.

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import random

h = ['a','b','c','d','e','f']
store = []
NumOfLetters = len(h)

for j in range(10):
if (h not in store):
print('not in')
store.append(h)
print(store)
for i in range(NumOfLetters):
l = random.randint(0,5)
letter = h[i]
h[i] = h[l]
h[l] = letter
print(store)

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everything works as intended when i run the loops separately, it's when I nest for loops where things go wrong.
I'm still new, so any advise will be much appreciated.

Answer 1

Mayank Dhillon I found the problem!

The way the code currently stands, a reference (not a copy) of `h` is being put in `store`. So even after shuffling `h`, it always "is" in `store` (the reference of `h` that is inside `store` is also shuffled).

That causes the `if` block to be entered only at the first iteration, and that's why the length of `store` is 1 in the end.

Passing a copy of `h` to `store` solves the problem. Like this:

store.append(h.copy())

Answer 2

You can use random.shuffle to perform that.

Also, you can swap values of variables in Python in one line:

h[i], h[l] = h[l], h[i]

Answer 3

You can also use random.sample() using the length of the list as the length of the sample. This code uses that principle (lines 23 - 28):
https://code.sololearn.com/ce35x5Xy1cSY/#py

Answer 4

I think I was not clear enough with my question
What I want is something like this
[['a', 'b', 'c', 'f', 'e', 'd'], ['a', 'b', 'c', 'd', 'e', 'f'], ['b', 'a', 'c', 'f', 'e', 'd']]
and I don't wan't the same sequences to be in list
that is, I don't want 2 of ['a', 'b', 'c', 'f', 'e', 'd'] in the "store" list

when is use:
\\\\\\\\\\\\\\\\\\\
if (h not in store):
store.append(h)
\\\\\\\\\\\\\\\\\\\\
only the shuffled "h" list generated at the end of loop is added to "store" list which means that there is only one element in the "store" list.
I'm sure I'm doing something wrong I just want to know what.

And thanks for informing me about random.shuffle() and h[i], h[l] = h[l], h[i]
this really shorten the code for me.

Answer 5

@Eduardo Petry
Thanks, I get it now. Really appreciate the help.