Question

在PyROOT中,它很容易从树中读到价值,即印刷页码<>val:

file = TFile( file.root )
tree = file.Get( tree )
for entry in tree: 
    print entry.val

还易于从中文本中读取数值:vector<float>,vec:

for entry in tree: 
    print entry.vec[1]

But what about nested vectors, i.e. nested of type vector<vector<float> >? Running

for entry in tree: 
    print entry.nested[0][0]

将扔下<条码>TypeError:矢量与带;vector<float>>物体是不可指数的。

What is the best way to deal with this? (better if it doesn t require loading in a ROOT dictionary)

Answer 1

这对我来说是用在平线上的指数计算。

    >>>from ROOT import *
    >>>vec1 = std.vector( double )()
    >>>vec2 = std.vector( double )()
    >>>vec_vec = std.vector(std.vector( double ))()

    >>>for i in range(3):
    >>>   vec1.push_back(i)
    >>>for i in range(5):
    >>>   vec2.push_back(i)
    >>>vec_vec.push_back(vec1)
    >>>vec_vec.push_back(vec2)

    >>>len(vec_vec)
    2
    >>>len(vec_vec[0])
    3
    >>>len(vec_vec[1])
    5
    >>>vec_vec[1][2]
    2.0

在你的例子中,错误说:

    TypeError:  vector<vector<float> >  object is unindexable

在打电话给构造者(类型)之后,你有不同的类型表明记忆空间的分配者正在工作。

    >>>type(vec1)
    <class  ROOT.vector<double,allocator<double> > >
    >>>type(vec_vec)
    <class  ROOT.vector<vector<double,allocator<double> >,allocator<vector<double,allocator<double> > > > >

To import such vectors from a TTree use setBranchAddress like in this example:

    >>>tree = file.Get( tree )
    >>>tree.SetBranchAddress("nested",vec_vec)
    >>>N = tree.GetEntries()
    >>>for i in range(N):
    >>>    vec_vec.clear()
    >>>    tree.GetEntry(i)
    >>>    print vec_vec[0][0]

Also note that this may be significantly faster after using

   >>>tree.setBranchStatus( * ,0)
   >>>tree.setBranchStatus( nested ,1)

友情链接