Flatten nested lists

flatten_nested_lists.py

def flatten_list(nested_list):
    """
    :param nested_list: a nested python list.
    Returns a flattened list. 
    """
    flattened_list = []
    for data_type in nested_list:
        if isinstance(data_type, list):
            flattened_list += flatten_list(data_type)
        else:
            flattened_list.append(data_type)
    return flattened_list

if __name__ == "__main__":
    print flatten_list(
        nested_list=[[1,2,[3]],4]
    )