custom attribute composition in graphml

[gabri94]

Hi, i realized that is not possible to write graph with custom object as attribute.
I was replacing them by their str representation just before saving, but I think this could be a cleaner and more general solution for the problem.
I already had open an issue #3237.

I'm not sure whether should be use str or repr. As a first try i used str, because it was much cleaner and linear than redefining make_str()
But I'm here for your feedback.

[dschult]

It looks like you have change the keyid to be "string" for unknown data types, but don't you have to change the code that generates the string? It's been a long time since I looked at this code -- and I am traveling so am short on time to investigate further right now.

Please also include a test in tests/test_graphml.py that writes a graph that has a custom object as a data attribute. Then read it back in and check that the result gives what you expect. The doc_string for the function will also need to be updated.

Thanks!

[gabri94]

There's a function called make_str() that is called on the value of all the attributes. For this reason i don't need to transform the Object to a string. The only thing preventing this is the check on the datatype of the attribute. So changing it to string when it's unrecognized is enough to have it converted.
My question is: make_str() takes the str of the object. Is that ok or the repr of the object shoud be used instead?

[dschult]

I actually don't know which would cause fewer surprises -- str or repr?
What would be best in your use-case?

[gabri94]

In my use case it would be the same since I made my custom object myself. Idk in a more general way what should be the difference

[dschult]

There are some discussions about the difference between repr and str. My understanding is that typically: str is a readable description of the object. repr is some text that unambiguously describes the object -- best case: repr shows python code that could regenerate the object.

In many cases they are the same. One that isn't is:
str("3")==str(3)=='3' but
repr("3")=="'3'" has an extra set of quotes, so it is the code that would create "3".

In the end it probably doesn't matter much, but if the goal is to be able to recreate the object perhaps repr would be better. If the goal is to make it readable, the str is better.