python::TChain::AddFriend(chain) have no result

ROOT
1

Hi! I have the following data structure: multiple root files, each file having a directory that have a set of trees. (each file have a different directory name)
It is assumed that for a set of files, the directory content will have the same trees.
I managed to do a chain with a given tree but i would like to add the rest of trees as friends,
so i reparse the filelist as many trees are in directory, create a chain for each and AddFriend it to the previous main chain. the problem is that nothing happens :slight_smile:
my tryout is here https://github.com/adriansev/AO2Dproto/blob/master/ao2d_process.py#L63
i really hope that is not a problem of ownership and persistence as i would assume that from the moment a chain is added as a friend, it’s persistence would be assured …
Any idea what is going on?
Thanks a lot!!

2

Hello,

i really hope that is not a problem of ownership and persistence as i would assume that from the moment a chain is added as a friend, it’s persistence would be assured …

I would try adding all the friend chains to a list to make them survive the loop, that will tell us if it’s an early garbage collection problem.

Please let us know how it goes!

3

so, i tried and no joy … see https://github.com/adriansev/AO2Dproto/blob/master/ao2d_process.py#L72
while the chains to be added are seen, adding them as friends show nothing when i try to print the chain with “all” that is supposed to show also all connected friends. the scan("*") also does not shows any other branches…

4

@pcanal can you spot any problem in the code that is adding the friends? Any thoughts on why their branches don’t show in chain.Scan(*)?

5

Any thoughts on why their branches don’t show in chain.Scan(*)?

Scan("*") does not implement prints the friend’s branches.

6

When printing the content of the list of friends, does it actually list of the friend you expect?

7

no, this part https://github.com/adriansev/AO2Dproto/blob/master/ao2d_process.py#L80
shows nothing …
but this https://github.com/adriansev/AO2Dproto/blob/master/ao2d_process.py#L72
show the proper content of the tree to be added as a chain, while the friend element is valid (i can call the ls method on it) but it show the empty message of:
Friend Tree: in file:

i would think that if the addition to the chain is unsuccessful, the returned friend element to be invalid/nullptr and method calling on it to break

8

well, never mind, looking over https://github.com/root-project/root/issues/9137 and checking entries
it seem that my “friends” have different number of entries so, my approach is invalid.