Also, the code below is the triangle.error.py file that given along. use this code for question 2. 

 

Write a program that replaces all the occurrences of an existing specified string from a text file with a new specified string. Your program should prompt the user to enter a filename, an existing string, and a new string. (For simplicity, convert all letters to lowercase.) Here is a sample run: Enter a filename: test.txt Enter the existing string to be replaced: morning Enter the new string to replace the existing string: evening Done