KeyError in EnergySystem.flows() after dump/restore

[jnnr]

Describe the bug
There is a KeyError in EnergySystem's flows method when called on a EnergySystem that has been dumped and restored: https://github.com/oemof/oemof.network/blob/96648132045837e58b008f114eae88ed66154007/src/oemof/network/energy_system.py#L176-L181

I found it when using oemof.solph.processing.parameter_as_dict. Getting the parameters of an EnergySystem is a useful step, e.g. in postprocessing.

The respective dictionary (see log below) contains a Bus with the proper name, but does not seem to totally fit. Maybe the EnergySystem is in an inconsistent state after deserialization? Any ideas @oemof-developer, @oemof/oemof-solph?

To Reproduce
Steps to reproduce the behavior:

1. Go to e.g. the basic example https://github.com/oemof/oemof-examples/blob/master/oemof_examples/oemof.solph/v0.4.x/basic_example/basic_example.py
2. insert this line before energysystem.dump() to see that it works
   energysystem.flows()
3. insert the line after energysystem.restore() to see it fail
4. Get an error traceback like this:

Traceback (most recent call last):
File "basic_example.py", line 226, in
solph.processing.parameter_as_dict(energysystem)
File "oemof-solph/src/oemof/solph/processing.py", line 378, in parameter_as_dict
flow_data = __separate_attrs(system, True, exclude_none)
File "oemof-solph/src/oemof/solph/processing.py", line 343, in __separate_attrs
components = system.flows() if get_flows else system.nodes
File ".virtualenvs/oemof-solph/lib/python3.6/site-packages/oemof/network/energy_system.py", line 179, in flows
for source in self.nodes
File ".virtualenvs/oemof-solph/lib/python3.6/site-packages/oemof/network/energy_system.py", line 180, in
for target in source.outputs
File ".virtualenvs/oemof-solph/lib/python3.6/collections/init.py", line 991, in getitem
raise KeyError(key)
KeyError: "<oemof.solph.network.Bus: 'natural_gas'>"

Expected behavior
The method should work after restoring. In particular, it should be possible to use parameter_as_dict after restoring.

Desktop (please complete the following information):

• OS: Xubuntu
• Python version 3.6.9

[henhuy]

What do you use for dumping and restoring?

[jnnr]

energysystem.dump() and energysystem.restore(), like in the basic example.

[henhuy]

Scheint als würden die outputs nicht korrekt restored, da folgende Zeile den Fehler wirft:
https://github.com/oemof/oemof.network/blob/dev/src/oemof/network/energy_system.py#L178

Denke, dass hat nichts mit der Funktion parameter_as_dict zu tun, eher mit dem dump/restore process...?!

[jnnr]

Scheint als würden die outputs nicht korrekt restored, da folgende Zeile den Fehler wirft:
https://github.com/oemof/oemof.network/blob/dev/src/oemof/network/energy_system.py#L178

Denke, dass hat nichts mit der Funktion parameter_as_dict zu tun, eher mit dem dump/restore process...?!

You are right, the KeyError is in the flows() method. So, it is actually a bug in the EnergySystem class of oemof.network. Does it make sense to open an issue there?

[henhuy]

sorry for en/de mixup...
Maybe rename issue and assign to some related people?

[sschlueters]

Hi there, I think I also stumbled upon this problem: oemof/oemof-network#10 (comment)

[henhuy]

This answers your question @jnnr - we can simply close this issue...

Duplicate of oemof/oemof-network#10

[jnnr]

Ok, if you say so. I just updated the title. But it is the same problem.

[henhuy]

Maybe you could ask if there is any progress?

[Bachibouzouk]

According to __getitem__() from the collection module the exception is raised only if

if key in self.data:

is False

Apparently the dict used for oemof outputs inherits from collection.UserDict (so I guess source.outputs.data would display something worth looking into?). Interestingly networks.Outputs overrides __delitem__, __setitem__ and __init__ of collection.UserDict but not __getitem__. Maybe the solution is to look there?

Sorry I don't have time to look into it further right now, I hope this might help to lead to finding the bug :)

[jnnr]

According to __getitem__() from the collection module the exception is raised only if

if key in self.data:

is False

Thanks for your feedback. That's right, the key in self.data gives False and causes the error. As I understand, it calls the __contains__ method of the dict, which also returns False. However, key in list(self.data) returns True.