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Library to assist programming, testing and execution of solutions for coding challenges like those on

Project description

Library to assist programming, testing and execution of solutions for coding challenges like those on

Find the full documentation at Readthedocs.

Author:Elmar Hinz
Documentation Server: Documentation Status

A Minimal Hello World Class <Add>

from challenges.challenge import Challenge

class Add(Challenge):
    sample = '''
        5, 6

    def build(self):
        self.model = self.line_to_integers(0)

    def calc(self):
        self.result = self.model[0] + self.model[1]

The class to write lets you focus on the core algorithms of the challenge while keeping stuff like opening, reading and writing of files out of the way. You inherit several methods to set up the model or to format your result for writing.

While the class variable sample just holds a minimal example of the input, the actual input is later injected by the Challenge Runner via the command line. In Bioinformatics this is often a large file of DNA.


See a more verbose example of HelloWorld.

The Challenge Runner Supports the Following Features

  • Listing available challenges
  • Scaffolding a new challenge directory, with a challenge class and a unit test class
  • Executing the small sample within the challenge class
  • Reading input files from the command line
  • Result output on the command line
  • Writing sample.txt and matching result.txt into the challenges directory
  • Running the unit test case of a challenge

The Layout of Your Directory Looks Like This

    ... more challenges ...

The names Challenge1 and Challenge2 are just placeholders for the names you choose during scaffolding.

Running the Challenge Runner

The directory myChallenges/ is the base directory of your challenges project. It’s the directory from where to use the Challenge Runner.

List the Available Challenges

prompt> challenge --list
* Challenge1
* Challenge2
* ...

Scaffolding a New Challenge

prompt> challenge --scaffold Challenge3

You now find the files:


Check it’s working by running the unit test case.

prompt> challenge --unittest Challenge3
Ran 1 tests in 0.001s


Run <sample> from the Class File

This is the small sample directly coded into the challenge class.

prompt> challenge --klass Challenge1
[the result output goes here]


You will automatically find the latest output in two files, independent from the input method you choose.


These files are just for convenience and are overwritten by the next run.

Read Sample from an Input File

prompt> challenge Challenge1 --file ~/Downloads/data.txt
[the result output goes here]

Storing Data and Results

Did you pass the challenge? Was the online grader content with the upload of latest.txt? Then you should store data and result.

prompt> challenge Challenge1 --file ~/Downloads/data.txt --write

You will find the files:


This files are stored until the next run with the –write flag.


To quickly see all available options.

challenge --help

Naming Conventions

The naming conventions follow the standards as defined by PEP 8 Style Guide for Python Code

There are two deliberate exceptions:

  1. Challenge module names are CamelCase:

    In contradiction to the style guide directories of the challenges are not all lowercase. Especially the first character must be uppercase. This is used to find and list the challenge directories between other modules. The directory and the class name must use the same word, with the .py extension for the file.

  2. Inherited class attributes and methods don’t have a leading underscore:

    The inherited functions and methods of the challenge are not a public API and the style guides recommends leading underscores. As inheritance is a core concept of the challenge class, this would lead to a hell of leading underscores. For this reason we don’t follow the style guide in this recommendation.


On useful advantage of naming the directory just like your challenge class is, that you can use the path expansion mechanism of the shell. Write the first characters of the class/directory name and hit <TAB>. Now you can use the directory name as name of the challenge. A trailing slash is discarded. The following two inputs are equivalent.

prompt> challenge -k HelloWorld
prompt> challenge -k HelloWorld/



This software requires Python 3.

Clone from Github

You can clone (or download) the Challenges project directly from Github. In this case the scripts and paths are not configured globally. Either you configure it globally or you place your challenges immediately into the projects folder so that the paths are detected relatively.

Put Your Challenges Immediately Into the Projects Folder

This is the most simple setup to get started. After downloading change into the download folder an try to run the HelloWorld unit test. In this case the command is in the bin directory, you call it as bin/challenge.

prompt> bin/challenge --unittest HelloWorld
Ran 3 tests in 0.001s


Now you are ready to create your challenge side-by-side with the HelloWorld challenge.

prompt> bin/challenge --scaffold MyChallenge

Use <pip> to Install <challenges>

If you have a fully configured python 3 environment up and running you can install <challenges> with pip3.

prompt> pip3 search challenges
prompt> pip3 install challenges

The library will be included into the python class path. The runner will be globally available as challenge or alternatively as stepik.

prompt> challenge --version
challenge 0.1.2

prompt> stepik --version
stepik 0.1.2

Project details

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Files for challenges, version 0.2.0
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