Triangle number: for nested loops in Python

Code snippet

n = int(input())
for a in range(0, n+1):
    for j in range(1, a+1):
        print(j, end=' ')
    print()

Input:

5

Output:

1 
1 2 
1 2 3 
1 2 3 4 
1 2 3 4 5

I had a problem while practicing coding. When I came across this piece of code, I didn't know how it worked. Please help me answer everyone!

Thanks everyone! :))

my guess is that the part you don't understand is this line:

print(j, end=' ')

What it does is print the number j, and then uses ' ' (i.e. space) as the end character.
Usually with the print function, the default end character is \n (on mac/linux) or \r\n on Windows which is a line feed, and the next print prints on a new line.

Here the number is printed, and then a space is printed, without a line feed. The next number is then printed on the same line after the space because we didn't print a line feed.
At the end of each first loop, there is a print(), which effectively prints nothing but a uses the default end character, and therefore prints a new line, and the next loop over the numbers starts at that new line.

for the lines:

for a in range(0, n+1): 
   for j in range(1, a+1):

the first line does a for loop over the range 0 to n (with a step size of 1). the `range is inclusive on the left and exclusive on the right, that is if n = 3, it goes over 0, 1, 2, 3

Second loop is the same but over 1 to a + 1, a being the value from the first loop, so it increases at each run of the loop.

The second loop runs inside the first one, so when a = 0, it runs 1 to 1 (1 time) and print 1, then a = 2, it runs for j = 1 and j = 2, and prints 1 2, when a = 2, second loop runs for j = 1, j= 2, j = 3, and print 1 2 3 and so on.
The first loop runs n times, so if n = 5 it prints 5 lines.