Thanks for the answers!
I saw both
Slides from '13 Users Workshop
Corresponding write-up
But as far as i can understand, there presented: slow python example and fast c++ example.
Which does not tell me how to write it to be fast in python.
And I looked at many threads on this topic, like:
Iteration over a tree in pyroot - performance issue
Pyroot, loop over TTree very slow compared to .C macro
But I still don’t understand how to improve reading TTree data…
I have tried one of @wlav replies:
x = array(‘d’,[0])
tree.SetBranchAddress( “x”, x )
alist, i = [], 0
while tree.GetEntry(i):
i += 1
alist.append( x[0] )
But I am getting the error:
SystemError: int TTree::GetEntry(Long64_t entry = 0, int getall = 0) =>
problem in C++; program state has been reset
There is thread about this error, but it related to TCloneArray. And he (maybe) solved this by
adding x.Clear(“C”) at the start of the loop. But there is no such method for this kind of array.
Is there a way to solve this?
Thanks