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# Documentation
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## What is documentation?
- Provides context for your work
- Allows your collaborators **and future you** to understand what has been done and why
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## Why document software?
Make your software reusable:
- A user should be able to run your software in the same way as you do now
- A user should be able to install your software
- A contributor should be able to add to, improve, or fix code
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## Documentation purpose types
Documentation can have different purposes:
- **User documentation**: What does the software do? How can it be used?
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- **Developer documentation**: How can your software be modified or extended?
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- **Deployment documentation**: What hardware and software requirements are there?
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## Documentation formats
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- In-code: intended for contributors (comments, docstrings, ...)
- README: simple text file, first thing that users/collaborators see
- Websites, Wikis
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## A good README file
+ README file is first thing a user/collaborator sees
+ What should be included in README files?
<ul>
<li contenteditable="true">...</li>
<li contenteditable="true">...</li>
<li contenteditable="true">...</li>
<li contenteditable="true">...</li>
<li contenteditable="true">...</li>
<li contenteditable="true">...</li>
<li contenteditable="true">...</li>
</ul>
Note:
+ A descriptive project title
+ Motivation (why the project exists) and basics
+ Installation / How to setup
+ Copy-pasteable quick start code example
+ Usage reference (if not elsewhere)
+ Recommended citation if someone uses it
+ Other related tools ("see also")
+ Contact information for the developer(s)
+ License information
+ Contributing guidelines
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## Why write in-code documentation?
In-code documentation:
+ Makes code more understandable
+ Explains decisions that were made
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## When **not** to use in-code documentation?
+ When the code is self-explanatory
+ To replace good variable/function names
+ To replace version control
+ To keep old (zombie) code around
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## Readable code vs commented code
```python=
# convert from degrees celsius to fahrenheit
def convert(d):
return d * 5 / 9 + 32
```
vs
```python=
def celsius_to_fahrenheit(degrees):
return degrees * 5 / 9 + 32
```
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## What makes a good comment?
**Comment A**
<pre data-id="code-animation"><code style="overflow: hidden;" data-trim class="python">
# Now we check if temperature is larger than -50:
if temperature > -50:
print('do something')
</code></pre>
**Comment B**
<pre data-id="code-animation"><code style="overflow: hidden;" data-trim class="python">
# We regard temperatures below -50 degrees as measurement errors
if temperature > -50:
print('do something')
</code></pre>
How are these different? Which one do you prefer?
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## Docstrings: a special kind of comment
```python=
def celsius_to_fahrenheit(degrees):
"""Convert degrees Celsius to degrees Fahrenheit."""
return degrees * 5 / 9 + 32
```
Why is this OK?
Note:
Docstrings can be used to generate user documentation.
They are accessible outside the code.
They follow a standardized syntax.
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## In-code commenting: key points
+ Explicit, descriptive naming already provides important documentation.
+ Comments should describe the why for your code, not the what.
+ Writing docstrings is an easy way to write documentation while you code, as they are accessible outside the code itself.
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## User/API documentation
+ What if a README file is not enough?
+ How do I easily create user documentation?
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## Tools
+ **Sphinx** / **mkdocs** (documentation generator)
- creates nicely-formatted HTML pages out of .md or .rst files
- programming language independent
+ **Github pages** (deploy your documentation)
- set up inside your GitHub repository
- automatically deploys documentation generated above
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## Take-home message
Documentation is a vital part of a project, and should be kept and created alongside the corresponding code.
Depending on the purpose and state of the project documentation needs to meet different criteria.
Documentation can take different shapes:
+ Readable code
+ In-code comments
+ Docstrings
+ README files
+ Tutorials/notebooks
