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[Python] Re-implement TTree.SetBranchAddress template call in Python #22247

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Merged
guitargeek merged 1 commit into from
May 13, 2026
Merged

[Python] Re-implement TTree.SetBranchAddress template call in Python #22247

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43 changes: 37 additions & 6 deletions bindings/pyroot/pythonizations/python/ROOT/_pythonization/_ttree.py
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Original file line number Diff line number Diff line change
Expand Up @@ -232,8 +232,7 @@ def _get_cpp_type_from_array_typecode(typecode):


def _determine_data_type(addr):
""" Figure out data_type in case addr is a numpy.ndarray or array.array.
"""
"""Figure out data_type in case addr is a numpy.ndarray or array.array."""

# For NumPy arrays
if hasattr(addr, "__array_interface__"):
Expand All @@ -260,6 +259,8 @@ def _SetBranchAddress(self, bname, addr, *args, **kwargs):
t.SetBranchAddress("my_vector_branch", v)
```
"""
import cppyy

import ROOT

branch = self.GetBranch(bname)
Expand All @@ -271,10 +272,37 @@ def _SetBranchAddress(self, bname, addr, *args, **kwargs):
# Figure out data_type in case addr is a numpy.ndarray or array.array
data_type = _determine_data_type(addr)

# We call the template specialization if we know the data type
func = self._OriginalSetBranchAddress if data_type is None else self._OriginalSetBranchAddress[data_type]

return func(bname, addr, *args, **kwargs)
if data_type is None:
return self._OriginalSetBranchAddress(bname, addr, *args, **kwargs)

# In the case the data_type is available, we would like to call the
# template overload of SetBranchAddress instantiatied for that type.
# However, there are two such overloads candidates:
#
# template <class T> int TTree::SetBranchAddress(const char *bname, T **add, ...);
# template <class T> int TTree::SetBranchAddress(const char *bname, T *add, ...);
#
# The cppyy bindings can't make a meaningful selection here as Python is
# lacking pointer semantics, so it considers both overloads as valid
# choices. In the past, we just happened to be lucky that it tried the T *
# overload first, which is the one we need. But as cppyy becomes more
# strict about overload resolution ambiguity errors, this won't work
# anymore. That's why we re-implement what happens in the template overload
# on the Python side.

cl = ROOT.TClass.GetClass[data_type]()
tp = ROOT.kOther_t
if not cl:
tp = ROOT.TDataType.GetType(cppyy.typeid(getattr(ROOT, data_type)))

# Extract the TBranch ptr argument if available
tbranch_ptr = ROOT.nullptr
if len(args) > 0:
tbranch_ptr = args[0]
elif "ptr" in kwargs:
tbranch_ptr = kwargs["ptr"]

return self._OriginalSetBranchAddress(bname, addr, ptr=tbranch_ptr, realClass=cl, datatype=tp, isptr=False)


def _Branch(self, *args):
Expand Down Expand Up @@ -314,6 +342,7 @@ def _TTree__getattr__(self, key):
out = ROOT._cppyy.ll.cast[cast_type](out)
return out


def _TTree_CloneTree(self, *args, **kwargs):
"""
Forward the arguments to the C++ function and give up ownership if the
Expand All @@ -327,6 +356,7 @@ def _TTree_CloneTree(self, *args, **kwargs):

return out_tree


@pythonization("TTree")
def pythonize_ttree(klass, name):
# Parameters:
Expand Down Expand Up @@ -380,6 +410,7 @@ def pythonize_tchain(klass):
klass._OriginalSetBranchAddress = klass.SetBranchAddress
klass.SetBranchAddress = _SetBranchAddress


@pythonization("TNtuple")
def pythonize_tntuple(klass):

Expand Down
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