Write a program that reads in a filename provided by the user, opens it and reads all of the lines. Create a dictionary to hold the line numbers for each valid identifier found. Your solution will need to process each line to determine whether a valid identifier exists on that line and if so, record both the line number and identifier found in the dictionary.

A valid identifier must be a string consisting of only letters, numbers, and underscores. If a line contains an invalid identifier no record is made in the dictionary. If a line contains a valid identifier already recorded in the dictionary append the line number to the dictionary log of where the identifier was found.

Here are some other requirements:

1. Keep provided test file intact

2. Use t4.py as your input test file to generate submission run output

3. Verify identifiers are valid; ignore if invalid

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special characters such as "@", "!", and "." are considered invalid identifiers, underscores and numbers (can also start with such) are considered valid identifiers.

I have seen other examples but the use 'import re' I don't, however, know much about that library so if it could be done without using it, would be great!

the file I am using contains the following:

apple

1

1

ball

art

dog

&

pen

rat

4

apple

1@.

carrot

!

orange

ant

ant

ant

ball

stick

pen

_

$a

***

goodbye