Python implementation of flatten an array

flatten_array.py

def flatten_array(arr):
    output = []
    for val in arr:
        if type(val) == list:                 # is the current value we are looking at is also a list
            output.extend(flatten_array(val)) # then recursive call itself to start from
                                              # the beginning and use python list extend 
        else:
            output.append(val)                # ok this is not a list just append to the bottom

    return output