How to have win32com code completion in IPython?

Question

Via

import win32com.client
wordapp = win32com.client.gencache.EnsureDispatch('Word.Application')

I can get a Word Application object documented e.g. here. However, ipython's autocompletion is not aware of that API, is there any way to add that?

Answer 1

Quick solution

Perhaps the simplest way to achieve code completion in IPython (tested with 6.2.1, see the answer below for a snippet that works with 7.1) and Jupyter is to run the following snippet:

from IPython.utils.generics import complete_object
import win32com.client

@complete_object.when_type(win32com.client.DispatchBaseClass)
def complete_dispatch_base_class(obj, prev_completions):
    try:
        ole_props = set(obj._prop_map_get_).union(set(obj._prop_map_put_))
        return list(ole_props) + prev_completions
    except AttributeError:
        pass

Short story long

With some more details being outlined in this guide, win32com ships with a script, makepy.py for generating Python types corresponding to the type library of a given COM object.

In the case of Word 2016, we would proceed as follows:

C:\Users\username\AppData\Local\Continuum\Anaconda3\pkgs\pywin32-221-py36h9c10281_0\Lib\site-packages\win32com\client>python makepy.py -i "Microsoft Word 16.0 Object Library"

Microsoft Word 16.0 Object Library
 {00020905-0000-0000-C000-000000000046}, lcid=0, major=8, minor=7
 >>> # Use these commands in Python code to auto generate .py support
 >>> from win32com.client import gencache
 >>> gencache.EnsureModule('{00020905-0000-0000-C000-000000000046}', 0, 8, 7)

The location of makepy.py will of course depend on your Python distribution. The script combrowse.py, available in the same directory, can be used to find the names of available type libraries.

With that in place, win32com.client will automatically make use of the generated types, rather than the raw IPyDispatch, and at this point, auto-completion is available in e.g. IPython or Jupyter, given that the COM object of interest actually publishes its available properties and methods (which is not a requirement).

Now, in your case, by invoking EnsureDispatch instead of Dispatch, the makepy part of the process is performed automatically, so you really should be able to obtain code completion in IPython for the published methods:

Note, though, that while this does give code completion for methods, the same will not be true for properties. It is possible to inspect those using the _prop_map_get_ attribute. For example, wordapp.Selection.Range.Font._prop_map_get_ gives all properties available on fonts.

If using IPython is not a strong requirement, note also that the PythonWin shell (located around \pkgs\pywin32\Lib\site-packages\pythonwin\Pythonwin.exe) has built-in code completion support for both properties and methods.

This, by itself, suggests that the same is achievable in IPython.

Concretely, the logic for auto-completion, which in turn relies on _prop_map_get_, can be found in scintilla.view.CScintillaView._AutoComplete. On the other hand, code completion in IPython 6.2.1 is handled by core.completer.IPCompleter. The API for adding custom code completers is provided by IPython.utils.generics.complete_object, as illustrated in the first solution above. One gotcha is that with complete_object being based on simplegeneric, only one completer may be provided for any given type. Luckily, all types generated by makepy will inherit from win32com.client.DispatchBaseClass.

If this turns out to ever be an issue, one can also circumvent complete_object entirely and simply manually patch IPython by adding the following five lines to core.completer.Completion.attr_matches:

try:
    ole_props = set(obj._prop_map_get_).union(set(obj._prop_map_put_))
    words += list(ole_props)
except AttributeError:
    pass

Conversely, IPython bases its code-completion on __dir__, so one could also patch gencache, which is where the code generation ultimately happens, to include something to like

def __dir__(self):
    return list(set(self._prop_map_get_).union(set(self._prop_map_put_)))

to each generated DispatchBaseClass.