Python challenge_9

Flatten a list

level of challenge 3/10

• Write a function that takes a list of lists and flattens it into a one-dimensional list.
• Name your function flatten.

• It should take a single parameter and return a list.

• For example, calling:

• flatten([[1, 2], [3, 4]])

• Should return the list:

• [1, 2, 3, 4]

Hint:

Start by defining an empty list as the result:

result = []

Then use a nested for loop to fill up the result.

# My solution

def flatten(out_list):
    new_list = [] 
    for in_list in out_list:
        for item in in_list:
          new_list.append(item)
    return new_list
print(flatten([[1, 2], [3, 4], [5, 6], [7, 8]]))

# Another Solution

def flatten(outer_list):
  return [
    item
    for inner_list in outer_list
    for item in inner_list
  ]

Add your solution in the comment :)