In comments section of PyCharm's manual there's a nice hint from developer:
#: :type: dict of (str, C)
#: :type: list of str
It works for me pretty well. Now it makes me wonder what's the best way to document parametrized classes in Python :).
Answer from Michael Korbakov on Stack OverflowVideos
In comments section of PyCharm's manual there's a nice hint from developer:
#: :type: dict of (str, C)
#: :type: list of str
It works for me pretty well. Now it makes me wonder what's the best way to document parametrized classes in Python :).
As pointed out in the PyCharm docs, a (legacy, pre-PEP-484) way of doing this is using square brackets:
list[Foo]: List of Foo elements
dict[Foo, Bar]: Dict from Foo to Bar
list of str, as suggested in the accepted answer, does not work as expected in PyCharm.
Starting with Python 3.5 and the implementation of PEP-484, you can also use type hints, which may be nicely supported by your IDE/editor. How this is easily done in PyCharm is explained here.
In essence, to declare a list return type using type-hinting (Python >=3.5), you may do something like this:
from typing import List
"""
Great foo function.
:rtype: list[str]
"""
def foo() -> List[str]:
return ['some string', 'some other string']
Here we declare (somewhat redundantly) that the function foo returns a list of strings, both in the type hint -> List[str] and in the docstring :rtype: list[str].
Other pre-declared types and more info can be found in the Python docs for typing.
Formats
Python docstrings can be written following several formats as the other posts showed. However the default Sphinx docstring format was not mentioned and is based on reStructuredText (reST). You can get some information about the main formats in this blog post.
Note that the reST is recommended by the PEP 287
There follows the main used formats for docstrings.
- Epytext
Historically a javadoc like style was prevalent, so it was taken as a base for Epydoc (with the called Epytext format) to generate documentation.
Example:
"""
This is a javadoc style.
@param param1: this is a first param
@param param2: this is a second param
@return: this is a description of what is returned
@raise keyError: raises an exception
"""
- reST
Nowadays, the probably more prevalent format is the reStructuredText (reST) format that is used by Sphinx to generate documentation. Note: it is used by default in JetBrains PyCharm (type triple quotes after defining a method and hit enter). It is also used by default as output format in Pyment.
Example:
"""
This is a reST style.
:param param1: this is a first param
:param param2: this is a second param
:returns: this is a description of what is returned
:raises keyError: raises an exception
"""
Google has their own format that is often used. It also can be interpreted by Sphinx (ie. using Napoleon plugin).
Example:
"""
This is an example of Google style.
Args:
param1: This is the first param.
param2: This is a second param.
Returns:
This is a description of what is returned.
Raises:
KeyError: Raises an exception.
"""
Even more examples
- Numpydoc
Note that Numpy recommend to follow their own numpydoc based on Google format and usable by Sphinx.
"""
My numpydoc description of a kind
of very exhautive numpydoc format docstring.
Parameters
----------
first : array_like
the 1st param name `first`
second :
the 2nd param
third : {'value', 'other'}, optional
the 3rd param, by default 'value'
Returns
-------
string
a value in a string
Raises
------
KeyError
when a key error
OtherError
when an other error
"""
Converting/Generating
It is possible to use a tool like Pyment to automatically generate docstrings to a Python project not yet documented, or to convert existing docstrings (can be mixing several formats) from a format to an other one.
Note: The examples are taken from the Pyment documentation
The Google style guide contains an excellent Python style guide. It includes conventions for readable docstring syntax that offers better guidance than PEP-257. For example:
def square_root(n):
"""Calculate the square root of a number.
Args:
n: the number to get the square root of.
Returns:
the square root of n.
Raises:
TypeError: if n is not a number.
ValueError: if n is negative.
"""
pass
I like to extend this to also include type information in the arguments, as described in this Sphinx documentation tutorial. For example:
def add_value(self, value):
"""Add a new value.
Args:
value (str): the value to add.
"""
pass
I need to write docstrings for every method and property in this file:
https://github.com/golemfactory/yapapi/blob/master/yapapi/services/service_runner.py
A couple questions.
Should you write a docstring for an init method? I suppose it depends? This one seems self explanatory. Should I just state what the code does? “ServiceRunner class is initialized with four parameters: job, instance, instance_tasks, and stopped.”
I could explain what each of those do. I actually have some questions about them. “Job” is clearly passed the string “job”, so I don’t understand the later call “job.id” - the string returns an ID?
As for: self._instances: List[Service] = [] - how can you pass an entire statement as an attribute? They convert “Service” to a list but then assign it as an empty list… will the result be the list of services or the empty list?
Just that for now. Please let me know if you understand this a bit better than I do.
Thanks very much