Question

In this exercise we will practice using nested loops. You will write s program that prompts the user to enter an integer between 1 and 9 and displays a pyramid of numbers, as shown in the example below.

The program must validate the input given by the user and make sure that:

• if the user enters a non-integer the program issues an error message and requests the user provides a valid input.
• if the user does not enter a number between 1 and 9 the program alerts the user of the mistake and requests the user enter a valid value.
• validation must be done using loops.

Here is a sample run:

Enter the number of lines (1 - 9): 10
Error: you must enter a value between 1 and 9. Try again.
Enter the number of lines (1 - 9): 0
Error: you must enter a value between 1 and 9. Try again.
Enter the number of lines (1 - 9): 4

   1
  212
 32123
4321234

Notes:

• The purpose of this problem is to practice using loops and try/except.
• Please make sure to submit a well-written program. Good identifier names, useful comments, and spacing will be some of the criteria that will be used when grading this assignment.
• This assignment can be and must be solved using only the materials that have been discussed in class. Do not look for alternative methods that have not been covered as part of this course.

How your program will be graded:

• correctness: the program validates input and produces the expected output: 40%
• complies with requirements: the program properly uses nested loops, try/except): 40%
• code style: good variable names, comments, proper indentation and spacing : 20%

Language is python 3

Answer 1

#Try block
try:
    #User input value
    number = int(input("Enter the number of lines (1-9): "))
    #Valditing the number, till user gives correct input.
    while number<1 or number>9:
        print("Error: you must enter a value between 1 and 9. Try again.")
        number = int(input("Enter the number of lines (1-9): "))
    #This for loop is used for counting number of rows from 1 to number
    for i in range(1,number+1):
        #Printing spaces by subtracting i from number
        for j in range(number-i):
            print(" ",end="")
        #Printing number from higher to lower from 3 to 1 or 2 to 1
        for k in range(i,0,-1):
            print(k,end="")
        #After 2 to 1 we need to print 2 and so on
        #For 1 there will be no another value
        #So, I write if condition and printing from 2 to i+1
        if i!=1:
            for k in range(2,i+1):
                print(k, end="")
        #Printing new line
        print()
#Except block
except ValueError:
    print("Enter only digits")

Sample input and output:

Enter the number of lines (1-9): 10
Error: you must enter a value between 1 and 9. Try again.
Enter the number of lines (1-9): 0
Error: you must enter a value between 1 and 9. Try again.
Enter the number of lines (1-9): 5
1
212
32123
4321234
543212345

Enter the number of lines (1-9): 10
Error: you must enter a value between 1 and 9. Try again.
Enter the number of lines (1-9): 0
Error: you must enter a value between 1 and 9. Try again.
Enter the number of lines (1-9): 4
1
212
32123
4321234