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Short python exercises you could do over and over
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README.md

kata-python

Kata is Japanese for form, as in patterns for practice. You practice the same pattern over and over until you're better at coding. Coding kata are short programs you can write over and over.

Origin

Most of these are inspired by an ancient book BASIC is Fun, which was a bunch of programs you could type and run on an 8 bit machine and as a by product maybe learn to write code. In retrospect, this was pretty crazy. Most of these are about as difficult as fizz-buzz, which as we know some people can't solve. I've been wanting to translate the code into a modern programing language since forever. Most of the problems were algebra story problems. The solved section isn't a translation of the original, coding styles are so radically different little would be salvagable from the original.

These questions are far easier than Cracking the Coding Interview. This set of problems isn't intended to work out if you've recently graduated from a CompSci program and still remember your algorithms and data structures classes.

As Interview Questions

If use in an interview, or as a take home question, in my opinion, solving these kata allow you to demonstrate:

  1. Speed. Can you solve it quickly.
  2. An ability to discuss code. Now that we have some real code, you can discuss specifications, design and algorithm chioces with the interviewer.
  3. Aptitude. If you can solve a simple question, no one knows if you are a good programmer. If you can't solve a simple question, it may be a bad sign.
  4. Proxy for a portfolio. If you know you interview poorly and can't write code with an audience, then it is imperative to do something else to demonstrate you can write code, such as putting together a portfolio of code samples that an interviewer can look and understand quickly. Developers' best code is probably locked behind non-disclosure agreements of various sorts and even if it wasn't, it sometimes so domain specific, large and mixed with other developers work that it is hard for an intervier to see what is going on.

See scoring for how a kata can be graded.

Kata Solving Workflow

If you want to do a kata, fork, clone and fill out the blanks in kata, kata_functiona, etc.

Run run_tests.sh to execute the tests. Initially they will pass, but that won't mean anything since the code under test is just place holder code. If your apps use a lot of blocking input, you may need to update your unit tests to only call the functions without blocking input commands.

I've started a syntax cheat sheet for looking up basic language questions. If you are doing an open book, open internet or doing the kata after consoluting a solved solution-- that will depend on what your motivations are. If you are practicing for whiteboarding, you won't have the internet handy.

Layout

The kata folder holds the blanks with some boiler plate filled in. If you are solving problems, branch and put your code here!

The kata_functional, kata_oop, kata_script are for kata problems to be solved with a particular programming style.

The solved folder has all the above solved. Except the ones I haven't gotten to yet. This is where you go to cheat or compare your code after you've already solved it.

You can make these as easy or as hard as you want, I recommend over-engineering the solution, but not so much that you can't finish it.

Easy

Medium

Harder

  • build it. This is an odd one out because a build script calls for a different knowledge base from writing a function.
  • text adventure Implement the navigation subsystem of a text adventure game.
  • sea battle Implement a tiny battle-ship game.
  • life ring A tiny game that gives you a chance to show various ways to search what could be represented as an array of bits.

Elements of the template

  • Common futures imports. Remove some friction by writing python 2/3 compatible code, at least for the easy things, like print, division and unicode literals
  • __init__ Your sample code is in a module
  • __module__ This allows the code to be run on python -m module_name
  • if __file__ == '__main__': This block runs if you execute python main.py
  • There is a minimal logger set up- you don't have to mix developer oriented logging and user oriented output, i.e. make appropriate choices about when to log and when to use print()
  • There is a skeleton for a unittest.
  • The parent fodler has a run_tests.sh bash command that will run all tests in all modules in \kata\
  • A build or setup.py script normally would be essential, but it introduces too many "knowledge points"

Python Interpretor, Libraries

I'm planning to write this in python 3 with some effort to make it python 2/3 compatible.

I plan to make some kata specifically for psycopg, pandas, and other libraries. At the moment, the goal is for all kata to be done with just the standard library and some development dependencies such as:

  • pylint
  • virtualenv, pyenv and similar

Some kata might be solvable with just an online fiddle/REPL, e.g. repl.it

Kata Design Workflow

I'm solving the problems first, then I copy the skeleton to the corresponding root folders.

If you want to fix bugs in my kata code, branch and modify the /solved/ folder and make pull requests.

Template

The template has some __future__ imports to do some minimum py2/py3 compatibility.

I want to discourage people from showing off code with horrible testability because it is peppered with input() and print() calls. What I'd really like to do is allow input() and print() in the run() method and disallow it in the supporting functions, but disabling one or the other for the whole file is a reasonable compromise.

I also wanted to encourage people to log correctly. Since these are all console applications, the expect output and the logging listener are writing to the same place. Proper logging only takes a few lines of code to set up, but is unrelated to demonstrating the skill in question. So I've provided an alternative to mixing logging prints() and application output prints().

I want the template to encourage unittesting, so there is a skeleton of a unittest. The each kata is a chance for you to demonstrate the ability to write testable code, the ability to set up a unittest skeleton is a distraction.

Professional code would have code + tests + a build script. Build scripts can be hard enough to write that writing a good build script would use up all the time available for a kata, so there is a stand alone kata for that and a pre-written build script.

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