Python: How To Multiply Each Value In A List Against All The Values In Another List

EDIT2: I have removed the rest of the code so I don't spoil the solution. Thank you for your help. EDIT: I included my whole code. I didn't want to include it because I didn't wan

Solution 1:

You need to use nested loop

x = []
y = []
products = []
palindromes = []

for i in range(10, 100):
    x.append(i)
# print(x)

for i in range(10, 100):
    y.append(i)
# print(y)

for i in range(len(y)):
    for j in range(len(x)):
        products.append(x[j] * y[i])


for i in range((len(products)-1)):
    a = str(products[i])
    b = tuple(a)
    c = b[::-1]
    if b == c:
        print('palindrome found!', a)
        print('b value:', b)
        print('c value:', c)
        palindromes.append(a)

solutions = list(map(int, palindromes))
solutions.sort()
print(solutions)

This is called the nested loop. Variable i is iterating for length of y minus 1 and variable j is iterating for length of x minus 1.

Solution 2:

There's no need to do

for i in range(10, 100):
    x.append(i)

You can make a list from a range object like this:

x = list(range(10, 100))

However, there's no need to make those x and y lists. You can create a list of the products by iterating directly over the ranges. For example:

products = []
for x in range(10, 100):
    for y in range(10, 100):
        products.append(x * y)

To make a list just containing the palindromes:

defis_palindrome(n):
    s = str(n)
    return s == s[::-1]

products = []
for x inrange(10, 100):
    for y inrange(10, 100):
        n = x * y
        if is_palindrome(n):
            products.append(n)

You can then do max(products) to find the highest palindrome that is the product of two two-digit numbers.

Here's a more compact way, using a generator expression, so it doesn't need to build a list:

r = range(10, 100)
print(max(filter(is_palindrome, (x * y for x in r for y in r))))

Solution 3:

Your for loop is equivalent to this:

products=[i*j for i in x[:-1] for j in y]

Solution 4:

You can use Kaushal Kumar Singh's solution, or here are two other solutions. However, in programming there is no universal solution, a lot of solutions can co-exist.

Code 1:

products = [i * j for i, j in zip(x, y)]

Code 2:

from operator import mul

products = list(map(mul, x, y))