Its been long that I want to automate many things but the creepy and complex syntax of shell scripts doesn’t let me do it. Somedays before while writing a script to monitor the memory usage of any process I decided to learn line scripts in python but never actually did it. Yesterday I saw an article from Vincent about the same topic. So finally I am doing it :)

One more thing Vincent is great as in the end I completely copied this article. There is no addition needed from my side.

There is a good comparison done by Vincent:

  1. Language: Shell has a creepy syntax and python is much more expressive.

  2. Distribution: Python comes with its own set of problems, though. Python runtime environments are typically a mess which may pollute people’s already cluttered global Python environments. With Python, installing a package is typically just a pip install <pkg> away, but it requires another tedious step: writing a setup.py.

    If it comes to distributing the script, a shell script may be much easier. With shell scripts it’s either a single file that needs to be copied somewhere. Manually, or via a make install command, which involves adding a Makefile and dealing with subtle differences for each Unix platform, not to even mention trying to run it on Windows machines.

  3. Argument Parsing: Each script will at some stage require some options or arguments. How should we do the argument parsing? Do I use getopt or getopts? Does it even matter? Can it take –long-form-options?

Solution

Lately, a few fantastic projects have taken away most of the tedious work surrounding the building of command line tools, and almost make it trivial now.

Click

Click is a Python library written by Armin Ronacher that deals with all the handling of command line option and argument parsing and comes with fantastic defaults. This project is a great step towards more consistent and standard CLI interfaces. Besides solving the options and argument parsing, it also has a ton of useful features packaged, like smart colorized terminal output, file abstractions, subcommands, and rendering progress bars.

pipsi

Using pipsi (also by Armin), users can install any Python command line script into an isolated Python runtime environment, so it solves the global cluttered Python environment problem entirely.

Cookiecutter

Cookiecutter (by the awesome Audrey Roy Greenfield) is a project generator, based on a predefined project template. It will read the template, ask the user a few questions to fill in the blanks, and generates a new project for you.

cookiecutter-python-cli

cookiecutter-python-cli is one such Cookiecutter template Vincent wrote that uses all of the above: it sports a predefined setup.py, a package structure that’s extensible, and test cases and a test runner to get you started.

Example

  1. First, install pipsi and follow its instructions:

    bash $ curl https://raw.githubusercontent.com/mitsuhiko/pipsi/master/get-pipsi.py | python

  2. Next, using pipsi, install Cookiecutter in its own isolated runtime environment:

    bash $ pipsi install cookiecutter

  3. Now use Cookiecutter to create your brand new project, based on my CLI template:

    bash $ cookiecutter https://github.com/nvie/cookiecutter-python-cli.git Cloning into 'cookiecutter-python-cli'... remote: Counting objects: 107, done. remote: Total 107 (delta 0), reused 0 (delta 0), pack-reused 107 Receiving objects: 100% (107/107), 12.82 KiB | 0 bytes/s, done. Resolving deltas: 100% (51/51), done. Checking connectivity... done. full_name (default is "Vincent Driessen")? Abhishek Gupta email (default is "vincent@3rdcloud.com")? abhi.bansal21@gmail.com github_username (default is "nvie")? knoxxs project_name (default is "My Tool")? sample_python_cli repo_name (default is "python-mytool")? sample_python_cli pypi_name (default is "mytool")? sample_python_cli script_name (default is "my-tool")? sample_python_cli package_name (default is "my_tool")? sample_python_cli project_short_description (default is "My Tool does one thing, and one thing well.")? release_date (default is "2015-04-15")? 2015-09-20 year (default is "2015")? version (default is "0.1.0")?

  4. When you’re done, you’ll have a project where you can run tox to run your test suite on all important Python versions. If you don’t need the test cases, simply remove the tests/ directory.

    bash $ tox

  5. Let’s install and run it without further modifications:

    bash $ pipsi install --editable . Running virtualenv with interpreter /Users/aapa/.local/venvs/pipsi/bin/python Using real prefix '/System/Library/Frameworks/Python.framework/Versions/2.7' New python executable in /Users/aapa/.local/venvs/sample-python-cli/bin/python Installing setuptools, pip, wheel...done. Obtaining file:///Users/aapa/Projects/sample_python_cli Collecting click (from sample-python-cli==0.1.0) Using cached click-5.1-py2.py3-none-any.whl Installing collected packages: click, sample-python-cli Running setup.py develop for sample-python-cli Successfully installed click-5.1 sample-python-cli Linked script /Users/aapa/.local/bin/sample_python_cli Done.

  6. Check it

    bash $ sample_python_cli Hello, world. $ sample_python_cli --as-cowboy Howdy, world. $ sample_python_cli --as-cowboy aapa Howdy, aapa.

Reference

  1. Writing a Command-Line Tool in Python
  2. getopt, getopts or manual parsing - what to use when I want to support both short and long options?
  3. Click
  4. Armin Ronacher
  5. pipsi
  6. Cookiecutter
  7. Audrey Roy Greenfield
  8. cookiecutter-python-cli