root_numpy.root2array(filenames, treename=None, branches=None, selection=None, object_selection=None, start=None, stop=None, step=None, include_weight=False, weight_name='weight', cache_size=-1, warn_missing_tree=False)

Convert trees in ROOT files into a numpy structured array.

Refer to the documentation of tree2array().


filenames : str or list

ROOT file name pattern or list of patterns. Wildcarding is supported by Python globbing.

treename : str, optional (default=None)

Name of the tree to convert (optional if each file contains exactly one tree).

branches : list of strings and tuples or a string or tuple, optional (default=None)

List of branches and expressions to include as columns of the array or a single branch or expression in which case a nonstructured array is returned. If None then include all branches that can be converted. Branches or expressions that result in variable-length subarrays can be truncated at a fixed length by using the tuple (branch_or_expression, fill_value, length) or converted into a single value with (branch_or_expression, fill_value) where length==1 is implied. fill_value is used when the original array is shorter than length. This truncation is after any object selection performed with the object_selection argument.

selection : str, optional (default=None)

Only include entries fulfilling this condition. If the condition evaluates to multiple values per tree entry (e.g. conditions on array branches) then an entry will be included if the condition evaluates to true for at least one array element.

object_selection : dict, optional (default=None)

A dictionary mapping selection strings to branch names or lists of branch names. Only array elements passing the selection strings will be included in the output array per entry in the tree. The branches specified must be variable-length array-type branches and the length of the selection and branches it acts on must match for each tree entry. For example object_selection={'a > 0': ['a', 'b']} will include all elements of ‘a’ and corresponding elements of ‘b’ where ‘a > 0’ for each tree entry. ‘a’ and ‘b’ must have the same length in every tree entry.

start, stop, step: int, optional (default=None)

The meaning of the start, stop and step parameters is the same as for Python slices. If a range is supplied (by setting some of the start, stop or step parameters), only the entries in that range and fulfilling the selection condition (if defined) are used.

include_weight : bool, optional (default=False)

Include a column containing the tree weight TTree::GetWeight(). Note that this will be the same value for all entries unless the tree is actually a TChain containing multiple trees with different weights.

weight_name : str, optional (default=’weight’)

The field name for the weight column if include_weight=True.

cache_size : int, optional (default=-1)

Set the size (in bytes) of the TTreeCache used while reading a TTree. A value of -1 uses ROOT’s default cache size. A value of 0 disables the cache.

warn_missing_tree : bool, optional (default=False)

If True, then warn when a tree is missing from an input file instead of raising an IOError.