a = [1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89]

def smallerThan(list, number=False):
    # if no number is provided in function call (e.g. smallerThan(a)), ask the user for one
    if not number:
        number = float(raw_input("What number should the numbers in the new list be smaller than? "))
    # create an empty list where the new numbers will be stored
    newList = []
    # iterate over each number (num) in the original list ("list" is and argument in the function definition)
    for num in list:
        # if the current number is smaller than the "number" argument, store it in the new list
        if num < number:
            newList.append(num)
    return newList
    
print smallerThan([4, 8, 93, 763, 34], 50)