CODEWITHSUNDEEP
pythonrecursion
MV912HB
MV912HB

Reputation: 61

Sequence using recursion

I am trying to write a function which outputs all possible combinations of char list with length and without any repeats like aa, bb etc.

I am now on this stage:

def sequences(char_list, n, lst = []):
    if len(lst) == n:
        print(lst)
    else:
        for i in range(len(char_list)):
            temp_list = [char_list[j] for j in range(len(char_list)) if i != j]
            sequences(temp_list, n, lst + [char_list[i]])

print(sequences(["a", "b", "c"], 2))

Output is correct but I have None at the end. I actually have no idea why.

['a', 'b']  
['a', 'c']  
['b', 'a']  
['b', 'c']  
['c', 'a']  
['c', 'b']  
None

And what is the best way to get strings in the output and not lists?

Upvotes: 0

Views: 42

Answers (3)

MV912HB
MV912HB

Reputation: 61

Well the problem was is that I printed it at the end once again.

Upvotes: 0

ForceBru
ForceBru

Reputation: 44838

The function sequences doesn't return anything (there's no return statement anywhere in the code), so it'll automatically return None. print(sequences(["a", "b", "c"], 2)) will execute this function and print its return value, outputting None.

To get strings instead of lists, concatenate all the strings in the list like this:

print(''.join(lst))

Upvotes: 1

Seth
Seth

Reputation: 2370

Every function has an implicit return None at the end of it. On the last line of your code, you asked Python the print the output of sequences, which is None since no return value was specified.

Upvotes: 0

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