There are 5 main patterns in Python, which can be used as building blocks for almost any pattern. They are:

• square
• increasing triangle
• decreasing triangle
• increasing right triangle
• decreasing right triangle

All the code is included in the repository.

The square is the simplest pattern, but its code can be used as a foundation to all the other patterns.

n = 5
for i in range(n):
    for k in range(n):
        print("*", end=" ")
    print()

By changing the nested loop's range to (i + 1) we now make it iterate from 1 to 5 times not just 5.

n = 5
for i in range(n):
    for k in range(i + 1):
        print("*", end=" ")
    print()

By changing the nested loop's range to (i, n) we now make it iterate from 0 to 5 on the first iteration, but i keeps increasing so we print less stars each iteration.

n = 5
for i in range(n):
    for k in range(i, n):
        print("*", end=" ")
    print()

In order to print a triangle on the right, we first have to print blank spaces. To do that, we just copy the decreasing triangle loop and replace the '*' with a blank space. After that bellow it, we paste the increasing triangle loop.

n = 5
for i in range(n):
    for k in range(i, n):
        print(" ", end=" ")
    for j in range(i + 1):
        print("*", end=" ")
    print()

The decreasing right triangle is almost the same, we just flip around the loop ranges of k and j.

for i in range(n):
    for k in range(i + 1):
        print(" ", end=" ")
    for j in range(i, n):
        print("*", end=" ")
    print()