CLI Calculator

In this project, you'll learn to create a tool that can be used from a command line interface (CLI). First, you'll see how you can directly pass Python code from the command line and create bash shortcuts to simplify the invocation. Second, you'll see how to use Python features to create a custom CLI application. Finally, you'll be given exercises to test your understanding and resource links for further exploration. The links to these sections are given below:

• Bash shortcuts
• Python CLI application
• Exercises

If you are on Windows, you can still follow along most of this project by skipping the bash specific portions. The CLI tool creation using argparse isn't tied to a specific OS. Use py instead of python3.9 for program execution. See docs.python: Windows command-line and the rest of that page for more details. Alternatively, you can use Windows Subsystem for Linux.

Project summary

• Execute Python instructions from the command line
• Use shell shortcuts to simplify command line typing
• Evaluate string content as Python code
• Create user friendly command line interfaces
• Allow stdin as source of user input

The following modules and concepts will be utilized in this project:

• docs.python: sys
• docs.python: argparse
• docs.python: eval
• docs.python: Modules
• docs.python: Exception handling

Real world influence

I had two main reasons to implement this project:

• learn how to write a CLI application
• a simple CLI calculator for personal use

There are powerful tools like bc but I wanted easier syntax without fiddling with settings like scale. Instead of writing a shell script to customize bc for my use cases, I went with Python since I wanted to learn about the argparse module too.