Edge aligned bin labels in ROOT

bin_labels.py

# coding: utf-8

# import root into a cage
import ROOT
ROOT.PyConfig.IgnoreCommandLineOptions = True
ROOT.gROOT.SetBatch()


# preps
canvas = ROOT.TCanvas()
canvas.Divide(1)
pad = [p for p in canvas.GetListOfPrimitives()if isinstance(p, ROOT.TPad)][0]
h = ROOT.TH1F("h", "", 10, 0., 1.)
axis = h.GetXaxis()

# disable default axis labels
axis.SetBinLabel(1, "")

# get margins and ranges
l = pad.GetLeftMargin()
r = pad.GetRightMargin()
b = pad.GetBottomMargin()
x_min = axis.GetXmin()
x_max = axis.GetXmax()

# some dummy edge values
edge_values = "abcdefghijklmnopqrstuvwxyz"[:axis.GetNbins() + 1]

# create edge labels
labels = []
for i, val in enumerate(edge_values):
    x = l + (1 - r - l) * i / axis.GetNbins()
    y = b - 0.01

    label = ROOT.TLatex(x, y, val)
    label.SetNDC(True)
    label.SetTextFont(43)
    label.SetTextSize(12)
    label.SetTextAlign(32)
    label.SetTextAngle(90)

    labels.append(label)

# draw and save
pad.cd()
h.Draw("HIST")
for label in labels:
    label.Draw()
canvas.SaveAs("bin_labels.png")