Pascal triangle pattern in Python

In this post, you will learn different ways to print Pascal triangle pattern in Python.

Pascal triangle is a number pattern that reflects a triangle. Firstly, 1 is set at the top, and afterward, we begin placing the numbers in a three-sided design. The numbers which we get in each progression are the addition of the over two numbers. It is like the concept of triangular numbers. Each new number lies between two numbers and below them, and its value is the sum of the two numbers above it.

Algorithm to Print Pascal's Triangle in Python

Get an input value from the user.
Using a for loop which ranges from 0 to n-1, append the sub-lists into the list.
Then append 1 into the sub-lists.
Then use a for loop to determine the value of the number inside the triangle.
Print the Pascal’s triangle according to the format.
Exit

Python program to print Pascal's Triangle

In the given example, first we ask the user to enter the number of rows that the Pascal triangle has. We use a for loop to append sub-lists into an empty list. Then append 1 to all the sub-lists. The for loop determines the value of the number inside the triangle which is the sum of the two numbers above it. The other for loop prints the Pascal's triangle.

num = int(input("Enter number of rows: "))
x=[]

for i in range(num):
    x.append([])
    x[i].append(1)
    for j in range(1,i):
        x[i].append(x[i-1][j-1]+x[i-1][j])
    if(num!=0):
        x[i].append(1)
        
for i in range(num):
    print("   "*(num-i),end=" ",sep=" ")
    for j in range(0,i+1):
        print('{0:6}'.format(x[i][j]),end=" ",sep=" ")
    print()

Output1:

Enter number of rows: 5
                     1
                  1      1
               1      2      1
            1      3      3      1
         1      4      6      4      1

Output2:

Enter number of rows: 7
                           1 
                        1      1 
                     1      2      1 
                  1      3      3      1 
               1      4      6      4      1 
            1      5     10     10      5      1 
         1      6     15     20     15      6      1