[Fix] ValueError: substring not found in Python

myStr = "I love Python!"

myStr.index('x')

ValueError                                Traceback (most recent call last)
Cell In[38], line 3
      1 myStr = "I love Python!"
----> 3 myStr.index('x')

ValueError: substring not found

Traceback (most recent call last):
  File "/Users/code2care/PycharmProjects/python-learnings/Strings.py", line 3, in <module>
    myStr.index('cool')
ValueError: substring not found

Process finished with exit code 1

Reason for this error

"ValueError: substring not found" error will occur when you make use of the index() function on a string to get a substring, but the substring is not found.

To fix this issue while working with the index() function have a if conditional check to see if a substring exists before using the index() function.

Example:

myStr = "I love Python!"

subStr = "cool"

if subStr in myStr:
    print(myStr.index(subStr))
else:
    print(f"Substring '{subStr}' not found in string '{myStr}'")

Output:

Substring 'cool' not found in the string 'I love Python!'