Question

When studying a snippet of unknown Python code, I occasionally bump into the

varName.methodName()

pattern.

To figure out what’s this, I shall study the code more, find where varName was instantiated, find its type. So if varName proves to be an instance of ClassName class, I would knew that methodName() is a method of ClassName.

Sometimes varName == self and methodName() is a method of this class, or a method inherited from some other class, if the current class is subclassing some other classes.

Are there quick ways / tools that could take ‘methodName’ as input, scan over all installed Python modules and show which classes have methodName()?

The closest thing related to this I know of is ipython. If I type a class name, then dot (‘.’) then TAB, it can show the class members. Instead of a class I could use a name of an object (which is an instance of a certain class) and it would work too. As soon as I choose a method name from the provided options, I can type ‘?’ or ‘??’ and get some help if there’s a docstring.

I wonder if ipython can do some intelligent scanning based only on ‘methodName’ string.

If you know alternatives to ipython that could possibly help with this, please do suggest them.

Edit: as requested, I’m explicitly adding that I would like a way to find methods by method names not only in Python source code files. Some Python packages (notably PyQt) contain a lot of .so files, and ipython is able to do completions by presumably importing them first. So a plain text search like grep (or even ctags) won’t do the trick here.

Answer 1

You want Exuberant ctags (old ctags doesn’t generate tags for Python).

Once you’ve installed (the way to do that depends on your platform), run it on your files:

$ /usr/local/bin/ctags *py

(you can run it multiple times to append tags to an existing tag file, have it recurse into subdirectories, etc, all with command-line options) and it makes a tags file like the following (for brevity I’m using a single Python file with one class defining a single method):

$ cat tags
!_TAG_FILE_FORMAT   2   /extended format; --format=1 will not append ;" to lines/
!_TAG_FILE_SORTED   1   /0=unsorted, 1=sorted, 2=foldcase/
!_TAG_PROGRAM_AUTHOR    Darren Hiebert  /[e-mail]/
!_TAG_PROGRAM_NAME  Exuberant Ctags //
!_TAG_PROGRAM_URL   http://ctags.sourceforge.net    /official site/
!_TAG_PROGRAM_VERSION   5.7 //
Foo a.py    /^class Foo(object):$/;"    c
amethod a.py    /^  def amethod(self): pass$/;" m   class:Foo

Now, quoting this article:

Let say when you discover a function
call which you wanna see the
definition, simply point the cursor to
that function and press ctrl ] and it
will bring you there. If you want to
go back to where you came from, simply
press ctrl t. Instead of ctrl t, I
like to use ctrl i and ctrl o to
travel to forward and backward of the
check points.

Also, control-P does (some attempt at) code completion for identifiers found in tags.
(:help tags in vim will give you more details).