Python
# Program to replace substring in a string
text = input("Enter main string: ")
old = input("Enter substring to replace: ")
new = input("Enter new substring: ")
result = text.replace(old, new)
print("Result:", result)Output
Enter main string: hello world Enter substring to replace: world Enter new substring: Python Result: hello Python
We use .replace(old, new) which returns a new string with all non-overlapping occurrences replaced.