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How PyDoc Helps Your Python Development
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This is Day 19 of the #100DaysOfPython challenge.
This post will use the
pydoc module from the standard library to to explore how we can navigate documentation as well as create our own.The code can be found on my GitHub repo.
Let's create the
hello-pydoc directory and set up the required files.# Make the `hello-pydoc` directory
$ mkdir hello-pydoc
$ cd hello-pydoc
# Create a folder to place our example files
$ mkdir src
# Create the required files
$ touch src/math.py main.py src/__init__.pyAt this stage, we have our files sorted and we can start to write some code.
PyDoc is a tool that allows us to explore the documentation of a module.
As a simple starter, we can use PyDoc to explore the documentation of the
datetime module from the command line.To do so, we can run
python -m pydoc [module] and we should see the output based on the doc strings for each of the functions in the module.Let's explore this for the
datetime module. From the command line, we can run the following command:$ python -m pydoc datetime
Help on module datetime:
NAME
datetime - Fast implementation of the datetime type.
FILE
/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/lib-dynload/datetime.so
MODULE DOCS
https://docs.python.org/library/datetime
CLASSES
__builtin__.object
date
datetime
time
timedelta
tzinfo
class date(__builtin__.object)
| date(year, month, day) --> date object
|
| Methods defined here:
|
| __add__(...)
x.__add__(y) <==> x+y
|
| __eq__(...)
# ... reset omitted for brevity ...When you run the command, it opens up the documentation for the
datetime module that can be traversed in the command-line.It gives us information on the following:
| Heading | Description |
|---|---|
NAME |
The name of the module. |
FILE |
The file that the module is defined in. |
MODULE DOCS |
The link to the documentation for the module. |
CLASSES |
The classes defined in the module. |
We can search within the docs by using the
/ or ? operator followed by a search term.For example, in my previous blog post
Datetime in Python, we heavily relied upon the datetime.datetime.now function.To search for that documentation, I can run
/ followed by now and one of the search results will return the following:now(tz=None) from builtins.type
Returns new datetime object representing current time local to tz.
tz
Timezone object.
If no tz is specified, uses local timezone.Tip: after searching, you can use the n key to navigate to the next result.
The above documentation tells us that the
now function returns a datetime object with the timezone's local time and date (with an optional argument of the timezone).Given this, we know that we could can the function both with and without an argument:
from datetime import datetime, timezone
datetime.now() # datetime.datetime(2021, 8, 7, 7, 22, 37, 216899)
datetime.now(timezone.utc) # datetime.datetime(2021, 8, 6, 21, 22, 30, 841500, tzinfo=datetime.timezone.utc)If we go searching for the synonymous function
utcnow, we can see the following:utcnow(...) from builtins.type
Return a new datetime representing UTC day and time.This tells us that there are no arguments but the returned value is a
datetime object with the timezone of UTC.from datetime import datetime
datetime.utcnow() # datetime.datetime(2021, 8, 6, 21, 24, 2, 865402)Now that we know the basics of searching PyDoc, let's now document our
math module.We can write and search for our own
docstrings.To demonstrate, add the following code to
src/math.py:def add(x, y):
"""add together two numbers
Args:
x (int): First number to add
y (int): Second number to add
Returns:
int: sum of x and y
"""
return x + yThe
docstring is a string that is used to document the function and is denoted as the comment between lines 2 and 10 of the code above.Tip: if you use VSCode, check out the docstring generator
Once we have that code in place, it is enough to view our own documentation for the module!
We can run
python -m pydoc src.math and we should see the output of the docstring:Help on module src.math in src:
NAME
src.math
FUNCTIONS
add(x, y)
add together two numbers
Args:
x (int): First number to add
y (int): Second number to add
Returns:
int: sum of x and y
FILE
/path/to/code/blog-projects/hello-pydoc/src/math.pyHow easy was that!
If we run
pydoc -h, we see the following:-h
pydoc - the Python documentation tool
pydoc <name> ...
Show text documentation on something. <name> may be the name of a
Python keyword, topic, function, module, or package, or a dotted
reference to a class or function within a module or module in a
package. If <name> contains a '/', it is used as the path to a
Python source file to document. If name is 'keywords', 'topics',
or 'modules', a listing of these things is displayed.
pydoc -k <keyword>
Search for a keyword in the synopsis lines of all available modules.
pydoc -p <port>
Start an HTTP server on the given port on the local machine. Port
number 0 can be used to get an arbitrary unused port.
pydoc -g
Pop up a graphical interface for finding and serving documentation.
pydoc -w <name> ...
Write out the HTML documentation for a module to a file in the current
directory. If <name> contains a '/', it is treated as a filename; if
it names a directory, documentation is written for all the contents.This gives us a list of the options that we can use to view our own documentation.
First of all, we will use the
pydoc -p 4000 option to start a server on port 4000.From here, you can open up
http://localhost:4000 in your browser and explore the documentation. The interface isn't pretty, but the job gets done.Finally, we can output the documentation as HTML by passing the
-w option to pydoc.Running
pydoc -w src.math outputs HTML into src.math.html which contains the following:<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<html>
<head>
<title>Python: module src.math</title>
</head>
<body bgcolor="#f0f0f8">
<table
width="100%"
cellspacing="0"
cellpadding="2"
border="0"
summary="heading"
>
<tr bgcolor="#7799ee">
<td valign="bottom">
<font color="#ffffff" face="helvetica, arial"
> <big
><big
><strong
><a href="src.html"><font color="#ffffff">src</font></a
>.math</strong
></big
></big
></font
>
</td>
<td align="right" valign="bottom">
<font color="#ffffff" face="helvetica, arial"
><a
href="file:/path/to/code/blog-projects/hello-pydoc/src/math.py"
>/path/to/code/blog-projects/hello-pydoc/src/math.py</a
></font
>
</td>
</tr>
</table>
<p></p>
<p></p>
<table
width="100%"
cellspacing="0"
cellpadding="2"
border="0"
summary="section"
>
<tr bgcolor="#eeaa77">
<td colspan="3" valign="bottom">
<font color="#ffffff" face="helvetica, arial"
><big><strong>Functions</strong></big></font
>
</td>
</tr>
<tr>
<td bgcolor="#eeaa77"><tt> </tt></td>
<td> </td>
<td width="100%">
<dl>
<dt>
<a name="-add"><strong>add</strong></a
>(x, y)
</dt>
<dd>
<tt
>add together two numbers
Args:
x (int): First number to add
y (int): Second number to add
Returns:
int: sum of x and y</tt
>
</dd>
</dl>
</td>
</tr>
</table>
</body>
</html>Today's post demonstrated how to use the
pydoc package to explore built-in and custom documentation.Albeit a shallow exploration, the best way to improve on your searching capability is to use the command line in practice.
Photo credit:
milada_vigerovaOriginally posted on my blog. To see new posts without delay, read the posts there and subscribe to my newsletter.
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