uproot_tree_utils

A small collection of utilities for handling ROOT TTrees with uproot.

Usage

There are two functions currently in the package. The first is clone_tree:

clone_tree(tree, new_filename, new_treename=None, branches=None, selection=None, new_branches=None)

The required arguments tree and new_filename are the TTree object to copy from (as retrieved by uproot) and the file to copy to, respectively. The simplest usage looks like

import uproot
from uproot_tree_utils import clone_tree

file = uproot.open('some_root_file.root')
clone_tree(file['the_treename'], 'a_new_filename.root')

This will simply copy the entire tree from the original file to a new file (with no other objects).

• new_treename can be used to give the new tree a different name. The default is the original tree's name.
• branches can be a list of strings representing the branches to copy. Only the selected branches will be in the new file.
• selection is an optional array determining which events to copy. This can be a boolean mask or integers corresponding to the desired event indices.
• new_branches allows the user to pass a dictionary of new branches to insert into the tree. The format for the dictionary should be {'new_branchname': array_with_branch_data}.

The other function available is write_tree:

write_tree(branches, filename, treename)

This function will create a new tree entirely composed of arrays passed to it.

• branches is a dictionary with items of the form 'branchname': array_with_branch_data
• filename is the name of a new file to put the tree in
• treename is the name of the new tree

Limitations

Not all branch types can be written by uproot.

Currently supported branch types:

• Char_t/char
• Short_t/short
• Int_t/int
• Float_t/float
• Double_t/double
• Long64_t/long long
• Bool_t/bool
• std::vector<short>
• std::vector<int>
• std::vector<float>
• std::vector<double>

Character strings, unsigned integers, vector<char>, and vector<bool> are not yet supported. There are also some known bugs with vector<long> and vector<long long>. Further nesting of vectors (e.g. vector<vector<int> >) is not supported by uproot's tree writing.