How to dynamically update a plot in a loop in Ipython notebook (within one cell)

Question

Environment: Python 2.7, matplotlib 1.3, IPython notebook 1.1, linux, chrome. The code is in one single input cell, using --pylab=inline

I want to use IPython notebook and pandas to consume a stream and dynamically update a plot every 5 seconds.

When I just use print statement to print the data in text format, it works perfectly fine: the output cell just keeps printing data and adding new rows. But when I try to plot the data (and then update it in a loop), the plot never show up in the output cell. But if I remove the loop, just plot it once. It works fine.

Then I did some simple test:

i = pd.date_range('2013-1-1',periods=100,freq='s')
while True:
    plot(pd.Series(data=np.random.randn(100), index=i))
    #pd.Series(data=np.random.randn(100), index=i).plot() also tried this one
    time.sleep(5)

The output will not show anything until I manually interrupt the process (ctrl+m+i). And after I interrupt it, the plot shows correctly as multiple overlapped lines. But what I really want is a plot that shows up and gets updated every 5 seconds (or whenever the plot() function gets called, just like what print statement outputs I mentioned above, which works well). Only showing the final chart after the cell is completely done is NOT what i want.

I even tried to explicitly add draw() function after each plot(), etc. None of them works. Wonder how to dynamically update a plot by a for/while loop within one cell in IPython notebook.

Answer 1

use IPython.display module:

%matplotlib inline
import time
import pylab as pl
from IPython import display
for i in range(10):
    pl.plot(pl.randn(100))
    display.clear_output(wait=True)
    display.display(pl.gcf())
    time.sleep(1.0)