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Write snippets of code in C++, Python, Ruby, and others as documentation and execute them as regression tests.

Project description

byexample is a literate programming engine where you mix ordinary text and snippets of code in the same file and then you execute them as regression tests.

It lets you to execute the examples written in Python, Ruby or whatever in your documentation and validate them.

You can always be sure that the examples are correct and your documentation is up to date!

Currently byexample supports:


How do I get started?

First, you need to install it:

$ pip install byexample                # install it # byexample: +skip

Or if you prefer, you can install it inside a virtual env.

If you don’t have pip or python installed, check the download page.

That’s it! Now, write a tutorial, a blog or a how-to and put some examples in between (like this that you are reading); All the snippets and examples will be collected, executed and checked.

$ byexample -l python,ruby,shell      # run it    # byexample: +skip
[PASS] Pass: <...> Fail: <...> Skip: <...>

You can select which languages to run, over which files, how to display the differences and much more.

The usage document goes through almost all the flags that byexample program has, full of examples of course.

What an example looks like?

It is just a snippet of code followed by the expected result:

>>> 1 + 2


1 + 2


The expression 1 + 2 is executed and the output compared with 3 to see if the test passes or not.

Where should I write the examples?

byexample really doesn’t care where you write the examples: you can write them in a Markdown, HTML, Latex, or plain text file.

Even you can write them in your own source code to document and test it.

Anything that it is between ```<language> and ``` is considered an example: this the Markdown fenced block syntax.

But byexample detects examples in other contexts as well.

For example in Python you can use the prompts >>> and ... to write an interpreter session like example.

>>> def add(a, b):
...   return a + b

>>> add(1, 2)

Take a look to the documentation of each language docs/languages.

Check out where should I write the examples section, it has a more in deep description.

And also check the usage page for more examples.

Languages supported

Currently we support:

  • Python (compatible with doctest) -> stable
  • Ruby -> experimental
  • Javascript -> experimental
  • Shell (sh and bash) -> stable
  • GDB -> experimental
  • C/C++ (using cling) -> experimental

More languages will be supported in the future. Stay tuned.


First off, thanks for using and considering contributing to byexample.

We love to receive contributions from our community. There are tons of ways you can contribute

  • add support to new languages (Javascript, Julia, just listen to you heart). Check this how to.
  • misspelling? Improve to the documentation is more than welcome.
  • add more examples. How do you use byexample? Give us your feedback!
  • is byexample producing a hard-to-debug diff or you found a bug? Create an issue in github.

But don’t be limited to those options. We keep our mind open to other useful contributions: write a tutorial or a blog, feature requests, social media…

Check out our CONTRIBUTING guidelines and welcome!

Extend byexample

It is possible to extend byexample adding new ways to find examples in a document and/or to parse and run/interpret a new language or adding hooks to be called regardless of the language/interpreter.

Check out how to support new finders and languages and how to hook to events with concerns for a quick tutorials that shows exactly how to do that.

You could also share your work and contribute to byexample with your extensions.


We use semantic version for the core or engine.

For each module we have the following categorization:

  • experimental: non backward compatibility changes are possible or even removal between versions (even patch versions).
  • provisional: low impact non backward compatibility changes may occur between versions; but in general a change like that will happen only between major versions.
  • stable: non backward compatibility changes, if happen, they will between major versions.
  • deprecated: it will disappear in a future version.

See the latest releases and tags

Current version:

$ byexample -V
byexample 7.4.5 (Python <...>) - GNU GPLv3
Copyright (C) Di Paola Martin -


This project is licensed under GPLv3

$ head -n 2 LICENSE     # byexample: +norm-ws
           Version 3, 29 June 2007

See LICENSE for more details.

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