Python: Find the index of a given string at which a given substring starts

Python String: Exercise-81 with Solution

Write a Python program to find the index of a given string at which a given substring starts. If the substring is not found in the given string return 'Not found'.

Sample Solution:-

Python Code:

def find_Index(str1, pos):
    if len(pos) > len(str1):
        return 'Not found'

    for i in range(len(str1)):

        for j in range(len(pos)):

            if str1[i + j] == pos[j] and j == len(pos) - 1:
                return i
                
            elif str1[i + j] != pos[j]:
                break

    return 'Not found'
print(find_Index("Python Exercises", "Ex"))
print(find_Index("Python Exercises", "yt"))
print(find_Index("Python Exercises", "PY"))

Sample Output:

7
1
Not found

Flowchart:

Visualize Python code execution:

The following tool visualize what the computer is doing step-by-step as it executes the said program:

Python Code Editor:

Have another way to solve this solution? Contribute your code (and comments) through Disqus.

Previous: Write a Python program to count number of substrings with same first and last characters of a given string.
Next: Write a Python program to wrap a given string into a paragraph of given width.