Day 44: Python Program To Print Pascal Triangle

 

def print_pascals_triangle(n):

    triangle = [[1]]

    for i in range(1, n):

        previous_row = triangle[-1]

        current_row = [1]  

        for j in range(1, len(previous_row)):

            current_row.append(previous_row[j - 1] + previous_row[j])

        current_row.append(1)  

        triangle.append(current_row)

        for row in triangle:

        print(" " * (n - len(row)), " ".join(map(str, row)))

rows = int(input("Enter the number of rows: "))

print_pascals_triangle(rows)

#source code --> clcoding.com

Code Explanation:

1. Function Definition

def print_pascals_triangle(n):

A function print_pascals_triangle is defined, which takes one argument n (the number of rows to generate).

2. Initializing the Triangle

    triangle = [[1]]

The triangle is initialized with a single row containing the number 1.

3. Building the Triangle

    for i in range(1, n):

        previous_row = triangle[-1]

        current_row = [1]  

A loop runs from 1 to n - 1, generating rows of the triangle:

previous_row: Refers to the last row of the triangle.

current_row: Starts with a 1, as every row in Pascal's Triangle begins with 1.

        for j in range(1, len(previous_row)):

            current_row.append(previous_row[j - 1] + previous_row[j])

For each position in the row (except the first and last), the value is calculated as the sum of the two numbers directly above it from the previous_row.

        current_row.append(1)

        triangle.append(current_row)

The row ends with another 1, and the current_row is appended to the triangle.

4. Printing the Triangle

    for row in triangle:

        print(" " * (n - len(row)), " ".join(map(str, row)))

Each row of the triangle is printed with formatting:

" " * (n - len(row)): Adds spaces to align rows, creating the triangular shape.

" ".join(map(str, row)): Converts numbers in the row to strings and joins them with spaces for proper display.

5. User Input and Function Call

rows = int(input("Enter the number of rows: "))

print_pascals_triangle(rows)

The program prompts the user to input the number of rows and calls the print_pascals_triangle function with the input.

Example Execution

Input:

Enter the number of rows: 5

Output:

     1

    1 1

   1 2 1

  1 3 3 1

 1 4 6 4 1