Removing bracket of a list

Question

This is a noob question. Lets say I have alist like this:

a=[[1,2,3],[4,5,6]]

How do I remove all brackets. I know how to use join() function to remove 1st level of brackets. But can't seem to remove all.

What do you mean by remove all the brackets? Are you just trying to make a string like `"1,2,3,4,5,6"`? You couldn't use `str.join` alone to even remove one level of brackets in a case like `[1,2,3,4,5,6]` (because the contents aren't strings), so it's not clear what you mean by "remove brackets" in the first place. — ShadowRanger, Dec 04 '21 at 02:53
How to flatten lists of lists: https://stackabuse.com/python-how-to-flatten-list-of-lists/ — Alex Reynolds, Dec 04 '21 at 02:55
I agree with ShadowRanger: it's not clear what you're trying to do. Please [edit] to clarify. BTW, welcome to Stack Overflow! Check out the [tour], and [ask] if you want tips. — wjandrea, Dec 04 '21 at 03:13

score 3 · Answer 1 · answered Dec 04 '21 at 02:54

3

One thing you can easily do is to use itertools.chain:

import itertools

a=[[1,2,3],[4,5,6]]

print(*itertools.chain.from_iterable(a), sep=', ') # 1, 2, 3, 4, 5, 6

It assumes the depth of nesting is two.

answered Dec 04 '21 at 02:54

j1-lee

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This is probably the fastest option. Look here (https://stackoverflow.com/questions/952914/how-to-make-a-flat-list-out-of-a-list-of-lists) – carlosdafield Dec 04 '21 at 03:02

score 1 · Answer 2 · answered Dec 04 '21 at 02:55

1

If you wish to end up with a string like "1,2,3,4,5,6" then you need to join each constituent list, then join those results.

",".join(",".join(lst) for lst in a)

answered Dec 04 '21 at 02:55

Chris

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carlosdafield · Answer 3 · 2021-12-04T02:59:44.043

This is a recursive function you can make to flatten a list.

It will work for your list a=[[1,2,3],[4,5,6]] and even weirder list like a=[[1,[2,3]],[4,[5],[6]]]

def flattenLst(lst):
    newLst = []
    _flattenLstHelper(lst,newLst)
    return newLst
    
def _flattenLstHelper(val,newLst):
    if not isinstance(val, list): # If it's not a list add to new list
        newLst.append(val)
        return
    for elem in val: # if it's a list recursively call each element
        _flattenLstHelper(elem,newLst)
        
print(flattenLst(a))

Removing bracket of a list

3 Answers3