Develop Reference

Python and Django Source Code Navigation in Emacs

I am wondering if there is a way to to navigate Python(Django) code in Emacs similar to how one can M-. for Common Lisp code when using SLIME.
I have installed ELPY and a mode called python-django. However, they do not seem to provide this functionality.
I am particularly interested in doing this why developing using Django. However, even navigation for standalone Python projects would be nice.

I will give dumb-jump a chance.
It is not as fancy as other go-to-definition methods, as it only searchs for some predefined regex in your project. But it simply works most of the time, and you can add your own regex if you need them.

Is there a way to view Python API documentation from within code?

I am looking for a Python IDE that will display the API (standard or third party module) documentations as pop-up when I hover over the code e.g. in eclipse if you hover over the java code it will give you the details of the functions or class, given the API documentation is setup in your IDE.
I can access the documentation from the respective web-site, but this not what I am looking for.
I am using PyCharm Community version, but could not find a way to see the documentation as quick view, also trying to find out if they support such feature at all. Anyone has any experience with any other IDE that will support such feature other than Eclipse.
TIA.

Visual Studio Code Python extension has a feature that will show the documentation of a documented code. Juts type the name of a function or a class and choose the one you want from the autocomplete list.
For example:
Here on the right you can see the code documentation. You can scroll down in that window to see all.
Hope this was helpful.

PyCharm autocomplete for imported modules

I'm new to Python and trying to get comfortable with the syntax and the language. I gave PyCharm a shot and found it very comfortable.
The only problem is that auto-completion isn't working as I expected and it is very important to me as part of the learning process and looking into some modules.
My code works even without the autocomplete but I'm very used to it and really wish to enjoy this feature.
I tried changing my project interpreter back and forth and nothing changed. I tried restarting PyCharm, the computer - didn't work. I tried Invalidate Cache, made sure the power save mode is off - nada.
Here is an example of missing autocomplete for lxml:
And here is the interpreter window:

Python is a dynamically typed language, so the return type of a function is not always known in advance. PyCharm generally looks at the source of a function to guess what it returns. It can't in this case because etree.parse is written in Cython, not Python. If you ask PyCharm to go to the definition of the function it gives you a stub.
The Python ecosystem has recently started to tackle this problem by providing various ways to annotate files with type hints for use by external tools, including PyCharm. One way is through .pyi files. A large collection of these can be found in the typeshed project. This issue shows that writing hints for lxml was proving difficult, and not wanting to have incomplete stubs in the typeshed repo, they were moved to their own repo here. The stubs are indeed very incomplete, and when I tried downloading and using them in PyCharm the results were pretty dismal. They correctly identify that etree.parse returns an etree._ElementTree, but the stub for _ElementTree only has two methods.
I got much better results by annotating directly in the Python file, e.g.
tree = etree.parse(path) # type: etree._ElementTree
(you can find out the type by checking type(tree))
PyCharm itself somehow knows what the methods on _ElementTree are so now autocomplete works. Unfortunately it seems that using .pyi files makes PyCharm forget this knowledge.
Here is documentation on type hinting in PyCharm.
And yes, in general you will have to get used to less autocompletion and general type information and static analysis. Fortunately I think there is a lot to make up for it that isn't possible in other languages :)

Install KITE, its a super fast auto suggest engine for python. It works for Pycharm,Sublime etc...
For more details view this youtube video

Search python docs offline?

In python I can get some rudimentary documentation for any object using help(<object>). But to be able to search the documentation, I have to go online. This isn't really helpful if I'm somewhere where the internet isn't accessible.
In R, there is a handy double question mark feature (??<topic>) that allows me to search through the documentation of all installed libraries for any function that includes <topic> in its name or documentation string. Is there anything similar for python? Perhaps even just for loaded objects?

pydoc comes with python and can do searches but only in the synopsis lines of available modules. Quoting pydoc --help:
pydoc -k
Search for a keyword in the synopsis lines of all available modules.
Note that into pydoc you can perform searches using "/".

Look in the python folder in the folder: Doc. This folder has the entire downloaded documentation of the python docs from python.org. I know this is a VERY late answer, but it brings up an easy solution.

This was mentioned in the comments already: Zeal
is similar to Dash but for Windows/Linux. It uses the same sources as Dash. It's built using Qt and is available in the repositories for several distros, for Ubuntu there is a PPA. Download it here.
Zeal is a simple offline API documentation browser inspired by Dash (OS X app), available for Linux and Windows.
Quickly search documentation using Alt+Space (or customised) hotkey to display Zeal from any place in your workspace.
Search in multiple sets of documentation at once.
Don't be dependent on your internet connection.
Integrate Zeal with Emacs, Sublime Text, or Vim. See Usage » Editor plugins for details.
It is open source (GPL), development happens on GitHub. Zeal uses the same stylesheets/HTML as the online docs, so everything should look familiar.
An in-browser alternative is devdocs.io. You can access the website even if you are offline, provided that you've marked them for local offline storage. You'll need to enable the Python 2 docs, and then mark them for offline storage here. However, as a longtime user of the online Python docs, I find the custom stylesheet that DevDocs uses a bit distracting.

Just to add another option for offline access of python docs (mostly core):
I don't have access to a linux computer at the moment, but on windows, you can navigate to your_python_dist_folder/doc to find some help files. Particularly python275.chm for instance.
If there's no doc folder on your linux machine, you can download the file here and google for a linux chm viewer:
https://www.google.com/search?q=linux+chm+viewer
::Note:
Some distributions also include docs for other packages in there... might be worth a check. Other than that, help(module) usually returns good information.
Edit:
You could get something that might be a little closer to what you want by using pydoc. E.g. you are looking for something about sin in the math module:
import math
import pydoc
[i for i in dir(math) if 'sin' in pydoc.getdoc(getattr(math,i))]
This would return the methods whose docstrings include sin:
['acos', 'acosh', 'asin', 'asinh', 'cos', 'cosh', 'isinf', 'sin', 'sinh']
for which you then could run the help() function

In case your working in a Mac there is Dash, which allows you to download docsets and then explore/search offline. Despite its documentation functionality, Dash is also a Snippet Manager.

Windows Idle - F1 from shell window or editing window gets you a windows help file of all the docs. I think it's better than the online version - it's easier to find stuff.

Although there are certainly better documentations built into your computer than help() like windows idle, another option for some of the more common topics would just be to save some of the online documentation to your computer. For the modules you use a lot and want to access offline, you could just download a text file version of the official online python documentation, which is the best place to get documentation. (file > save page as > select .txt file format)

This may not have been available at the time the question asked and answered, but python.org now makes all the documentation available online as an archive of HTML files which can be navigated and searched offline: https://docs.python.org/2/download.html
(The link directs to docs for the latest version of 2.x, but you can choose 3.x and older 2.x versions from that page)

You should try ipython.
object_name? will print all sorts of details about any object,
including docstrings, function definition lines (for call arguments)
and constructor details for classes.
The magic commands %pdoc, %pdef, %psource and %pfile will respectively print the docstring, function definition line, full source code and the complete file for any object (when they can be found). If automagic is on (it is by default), you don’t need to type the ‘%’ explicitly.

Has anyone found a good set of python plugins for vim -- specifically module completion?

I'm looking for a suite of plugins that can help me finally switch over to vim full-time.
Right now I'm using Komodo with some good success, but their vim bindings have enough little errors that I'm tired of it.
What I do love in Komodo, though, is the code completion. So, here's what I'm looking for (ordered by importance).
Code completion, meaning: the ability to code complete modules/functions/etc. in any module that's on the pythonpath, not just system modules. Bonus points for showing docstrings when completing.
Jump-to a class definition. I'm guessing CTAGS will do this, so how do you all manage automatically updating your tags files?
Project type management for managing buffers: ideally the ability to grep for a filename in a directory structure to open it. Bonus for showing an index of class definitions while a buffer is open.
Bzr integration. Not super important, since most of it I can just drop to the shell to do.

Here you can find some info about this.
It covers code completion, having a list of classes and functions in open files. I haven't got around to do a full configuration for vim, since I don't use Python primarily, but I have the same interests in transforming vim in a better Python IDE.
Edit: The original site is down, so found it saved on the web archive.

And I write another plugin: https://github.com/klen/python-mode
Old (now its more powerful) screencast here: https://www.youtube.com/watch?v=67OZNp9Z0CQ

Old question, but I typed all this up for a misread question...
General plugin recommendations: LookupFile and a plugin for your source control system (I like Git and Git-Vim).
Python plugin recommendations: If you're using Linux, I'd recommend ipython and ipy.py (a better interactive interpreter). Improved syntax highlighting, snippets, pydoc, and for refactoring support bicyclerepairman. I got started with this post.
You may want to try looking through someone's vimfiles. Mine are on github.

For refactoring: ropevim

Here is some info on Bazaar integration if you're interested:
https://launchpad.net/bzr-vim-commands

I use pydoc.vim (I actually wrote it) a lot, try it and tell me what you think. Another one that I think is quite useful is the updated syntax file with all it's extensions that you can enable, which you can find here.

I use Pydiction (http://www.vim.org/scripts/script.php?script_id=850) it's a plugin for vim that lets you Tab-complete python modules/methods/attributes/keywords, including 3rd party stuff like Pygame, wxPython, Twisted, and literally everything. It works more accurately than other things i've tried and it doesn't even require that python support be compiled into your Vim.

Code completion: PySmell looks promising. It's work-in-progress, but alredy useful.

I personally thinkJedi Vim is the best, but it is incompatible with python-mode.