_tcanvas.pyzdoc

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\pythondoc TCanvas
 
The TCanvas class is used to create the canvas on which graphical objects such as histograms can be drawn. The following
is a simple example of typical usage:
 
\code{.py}
import ROOT
import numpy
 
 
def plot():
    h = ROOT.TH1D("h", "h", 100, -5, 5)
    h.Fill(numpy.random.normal(size=1000))
 
    c = ROOT.TCanvas()
    h.Draw()
    c.Draw(block=True)
 
 
if __name__ == "__main__":
    print("Before plot function")
    plot()
    print("After plot function")
\endcode
 
Note the optional argument `block` passed to the `Draw` method of the canvas. If set to `True`, it will block the script
execution and run the ROOT graphics event loop until the <space> key is pressed. This allows interacting with the
canvas and its content until necessary, then move on with the rest of the script.
 
Another relevant use case is drawing live updates on a canvas, shown in the example below. In this case, the canvas is
setup by first creating the object to be drawn and drawing it once. Then, the object is updated in a for loop, which
could represent for example an incoming stream of data with which the histogram should be filled. Each time the plot
should be updated, the `ModifiedUpdate` function should be called. This will immediately show the new contents on the
plot. Finally, the canvas is drawn again with `Draw(block=True)` at the end of the loop so that it stays visible and can
be interacted with.
 
\code{.py}
import ROOT
import numpy
 
 
def live_update():
    c = ROOT.TCanvas()
    h = ROOT.TH1D("h", "h", 100, -5, 5)
 
    h.Draw()
    for _ in range(100):
        h.Fill(numpy.random.normal(size=10))
        c.ModifiedUpdate()
    c.Draw(block=True)
 
if __name__ == "__main__":
    print("Before plot function")
    live_update()
    print("After plot function")
\endcode
 
\endpythondoc