制作大小可变的列表列表

Question

I'm writing a program that will accept up to five numbers and find if they're prime or not. If a number is not prime it will find their prime factors. Then it will calculate the LCM of the initial numbers. The code I've written so far is this:

def prime(n):
    if n > 1:
        for i in range (2,n):
            if n % i == 0:
                return False
    return True
def length(n):
    if len(n) > 5:
        return True
    return False
toggle = False
enter_numbers = True
zero_one_neg = True
square = False
prime_list = [ [] for i in range(100) ]
lcm_list = [ [] for i in range(100)]
while enter_numbers:
    nums = list(map(int, input('\nEnter up to five natural numbers greater than 1 separated by commas. Enter at least two if you want to calculate their LCM: ').split(',')))
    for i in range (len(nums)):
        if nums[i] <= 1:
            zero_one_neg = True
            print('\nNo zeroes, ones or negatives. Start over. ')
            if length(nums) and zero_one_neg:
                print('\nNo more than five numberes. Start over. ')
                break
            break
        else:
            zero_one_neg = False
    if length(nums) and not zero_one_neg:
        print('\nNo more than five numbers. Start over. ')
    elif not length(nums) and not zero_one_neg:
        enter_numbers = False
for i in range (len(nums)):
    for j in range (2,nums[i]):
        if nums[i] % j == 0:
            lcm_list[i].append(j)
            if prime(j):
                prime_list[i].append(j)
            toggle = True
    if not toggle:
        print('\n', nums[i] ,'is a prime number.')
    if toggle:
        print('\n', nums[i] ,'is not a prime number. It\'s prime factors are: ',prime_list[i])
        print(lcm_list[i])
        toggle = False
print(len(prime_list))

It's not complete of course. It runs ok but I don't like the fact i have to preset the sizes of prime_list and lcm_list . How can I dynamically set their sizes?

Answer 1

Instead of initializing the lists with a certain number of empty sublists, you can initialize them as empty lists, and append a new empty sublist for each iteration:

lcm_list = []
prime_list = []
for i in range(len(nums)):
    lcm_list.append([])
    prime_list.append([])
    for j in range(2, nums[i]):
        ...

Answer 2

When you append you just have to have the values in square brackets to add a list into your list

a = []
b = [2,3]
c = [3]

#start with an empty array
print(a)
#[]

#add additional lists with whatever, this one has 2 values
a.append(b)
print(a)
#[[2, 3]]

#this just pushes the one
a.append(c)
print(a)
#[[2, 3], [3]]