Arguments

Bookbot is done! Almost...

You've probably noticed that most CLI tools you're used to (ls, cd, git, etc.) aren't limited to a single "hard coded" input. Right now bookbot can only analyze books/frankenstein.txt. That's not very useful, is it? Let's update the program so that we can pass it a path to our book instead of using a hardcoded value.

System Arguments

The built in sys module provides access to command line arguments. In particular sys.argv is a list of strings representing the arguments passed to the script. The first argument is the script name, the rest are the arguments.
For example, python3 main.py will result in a sys.argv list that looks like this:

print(sys.argv)
# Prints ['main.py']

And python3 main.py books/frankenstein.txt will result in a sys.argv list that looks like this:

print(sys.argv)
# Prints ['main.py', 'books/frankenstein.txt']

print(sys.argv[0])
# Prints 'main.py'

print(sys.argv[1])
# Prints 'books/frankenstein.txt'

Assignment

Remove any hard coded book paths from your code, we'll get the path from the command as shown above.
At the top of main.py, import the built-in sys module:

import sys

In your code, check if the sys.argv list has two entries, if not:
- First print a message explaining how to use the program: Usage: python3 main.py <path_to_book>
- Then exit the program with a status code of 1 using sys.exit(1)
Use the second argument in sys.argv as the path to the book file instead of the hardcoded path.
Test your program with python3 main.py books/frankenstein.txt and make sure it works as expected.
Download some more books and test your program with them, adding them to the books directory and passing them in as CLI arguments when you run your program. Add at least these two books:
- books/mobydick.txt
- books/prideandprejudice.txt

Use the books that are linked above, or the CLI tests will fail.

You can also run the following command to download and create the files:

wget -O books/mobydick.txt https://storage.googleapis.com/qvault-webapp-dynamic-assets/course_assets/mobydick.txt
wget -O books/prideandprejudice.txt https://storage.googleapis.com/qvault-webapp-dynamic-assets/course_assets/prideandprejudice.txt

Run and submit the CLI tests.