Python objects have an attribute called
__doc__ that provides a documentation of the object. For example, you simply call
Dog.__doc__ on your class
Dog to retrieve its documentation as a string.
You can define the docstring using a string surrounded by triple quotes as shown in the example:
class Dog: """Your best friend.""" def do_nothing(self): pass print(Dog.__doc__) # Your best friend.
Try it yourself in the interactive Python shell:
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Let’s go back to the docstring. As everything is an object in Python (even functions), you can also define a docstring on functions:
def bark(): """Wuff""" pass print(bark.__doc__) # Wuff
Note that if you don’t define the docstring, the return value is
def bark(): pass print(bark.__doc__) # None
Why Using Docstrings?
A great advantage of having defined docstrings in your code is that you now can create your own great-looking documentation programmatically. With tools such as Sphinx, it’s super easy to create something like this for your own code projects–only using the
__doc__ values defined in the code.
Best Practices Docstring
There are a couple of best-practices called Docstring Conventions as defined in the official PEP standard. Adhere to them when defining your docstrings. Here are the 7 most important docstring conventions:
- All modules, function, methods, and classes should have docstrings.
- Always use
"""triple double quotes"""around your docstrings for consistency reasons.
- Use triple quotes even if the docstring fits into a single line. This allows for easy expansion later.
- No blank line before or after the docstring—except for classes where you should add one line after the docstring.
- Use a phrase that describes what your code is doing such as
"""Do X and return Y."""ending in a period. Don’t use a description such as
"""Does X and returns Y.""".
- Multi-line docstrings start with a summary line (like the one-liner docstring), followed by a blank line, followed by a closer description such as
argument --- name of the person (string)to describe one of the arguments of the function or method. For example, you can use one line per argument.
- Start a multi-line docstring immediately in the same line of the opening
"""triple double strings...rather than starting the text in a new line.
If you’re a perfectionist or beyond intermediate code level, check out the official documentation that contains more examples.
Where to Go From Here?
Enough theory, let’s get some practice!
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