3 Ways To Flatten Any List In Python

Learn how you can flatten any list in Python. We will be exploring 3 different ways to do this. First will be through vanilla Python with the for loop, then we will use the faster list comprehension approach, and finally we will use the easiest approach with numpy.

[@hydra147147]

One can also try this implementation: def flatten_any(input_list: list) -> list: return sum(map(flatten_any, input_list), []) if isinstance(input_list, list) else [input_list]

[@Indently]

Works great! Although it's incredibly difficult to read, but that can be really hard to avoid if you want short code to flatten lists.

[@jbn999]

FYI - This was my interview question with Facebook. - Recursion would make anything flat whatever your throw at it.

[@wartem]

Well, you have to handle call stack issues when throwing "whatever" at it. It has limits and recursion isn't recommended in production code.

[@alexisdamnit9012]

I was surprised this video didn't have a recursion solution. smh

[@ezrawick]

Great! I was looking for this solution last week.

[@treadaar]

lst = [[[[1,2],[3,4,['some', 'text']]],[[5,6, [0, ['l', 'j']]],[7,8]]],[9]] print(lst) # recursively flatten list using yield from to generate a new list def flatten_list(lst): for item in lst: if isinstance(item, list): yield from flatten_list(item) else: yield item print(list(flatten_list(lst))) I would use this, much easier and flattens any number of nested lists with any content.

[@padraic1983]

Just turn the array into a string , use list comp to filter

[@padraic1983]

Lol of course that's just being cheap ;)

[@wartem]

Or regex

[@padraic1983]

@@wartem that's why I said I was being cheap

[@j.raimundosilva2101]

I have a clean pythonic way to do this, but if the first index of the deepest item is list, set ou tuple, it ends the flatten function: def flatten(input_list) -> list: flatten_layer = [item for subitem in input_list for item in subitem] if not isinstance(flatten_layer[0], (list, tuple, set)): return flatten_layer return flatten(flatten_layer) if you copy this function you will see that it flattens any dimension of list given its other limits.

[@ZeroSleap]

So basically at first you just showed two functions to flatten them yourself and at the end you succumbed to using a superior implementation from numpy.Ok i guess. I was expecting a recursive approach,but alright.

[@Indently]

I will post an updated version with recursive approach.

[@sammflynn405]

what's wrong with flatten = list(itertools.chain(*list_any))