Re: [igraph] Union of two graphs keeping attributes

[Tamas Nepusz]

> Is it possible to insert into next igraph? Should I go ahead and send a 
> pull request on github?
If you send me a patch or a pull request on Github, I will integrate it into
the next release (probably 0.7) if possible. Note that a pull request would
require a bit more work:

- add a docstring to the function in Epydoc format

- make it a method of the Graph class

- it should work with more than two graphs; note that Graph.union() allows
you to specify more than one graph and it would merge the graphs in the
arguments into the current graph

- add a test case in igraph/test/operators.py

If you can do these, that would be great. If you don't have time for it,
that's okay, just file a request in the issue tracker on Github and I will
do it sooner or later.

> How would you call it? An option on Graph.compose()? It's not a real 
> union, it's more the reverse of a decompose() operation.
I would simply override the current Graph.union() implementation; it could
have a keyword argument named "keep_attributes" with a default value of
False (for sake of compatibility). Setting it to True could invoke your
solution, while setting it to False could invoke the original implementation.

Cheers,
Tamas