Give TMultiGraph and THStack an __iter__ method

ROOT
1

Hey, it would be cool if the two collections for graphs and histograms, TMultiGraph and THStack would naturally support iterating over them in Python.

All that is needed is basically:

ROOT.THStack.__iter__ = lambda self: iter(self.GetHists())
ROOT.TMultiGraph.__iter__ = lambda self: iter(self.GetListOfGraphs())

or, if done properly:

class ROOT.THStack(...):
    ...
    def __iter__(self):
        return iter(self.GetHists())

With this it becomes trivial to do, e.g.:

h1 = ROOT.TH1D("h1", "h1", 100, 0, 100)
h2 = ROOT.TH1D("h2", "h2", 100, 0, 100)
stack = ROOT.THStack()
stack.Add(h1)
stack.Add(h2)
for hist in stack:
    print hist.GetTitle()
1 Like
2

Hi,

Good idea! All we need is begin() and end() for these two classes. Would you mind sending in a pull request at https://github.com/root-mirror/root ?

If you don’t want to code it then we’ll do it - let me know!

Axel.

3

Hey,

I’m not exactly sure how to proceed on that one. Do I need to find the explicit python binding of THStack or would I need to implement it in the C++ class so it would automatically be picked up?

Andreas

4

Also, for Python’s full iterator interface you need to implement the __iter__ method and the next (or __next__ for Pyhton3) method?

5

Hi - sorry, I was too terse. Here’s the deal: once the C++ classes have begin() and end(), PyROOT will recognize them as iterable and map what’s needed to the python world.

I.e. all that’s missing is begin() and end() methods for the C++ classes.

Cheers, Axel.

6

Hey Axel,
have a look at the PR: https://github.com/root-mirror/root/pull/371

1 Like