Overwrite previous output in jupyter notebook

Question

Let's assume I have a part of code that runs for some specific amount of time and each 1 second outputs something like this: iteration X, score Y. I will substitute this function with my black box function:

from random import uniform import time  def black_box():     i = 1     while True:         print 'Iteration', i, 'Score:', uniform(0, 1)         time.sleep(1)         i += 1 

Now when I run it in Jupyter notebook, it output a new line after each second:

Iteration 1 Score: 0.664167449844 Iteration 2 Score: 0.514757592404 ... 

Yes, after when the output becomes too big, the html becomes scrollable, but the thing is that I do not need any of these lines except of currently the last one. So instead of having n lines after n seconds, I want to have only 1 line (the last one) shown.

I have not found anything like this in documentation or looking through magic. A question with almost the same title but irrelevant.

Answer 1

@cel is right: ipython notebook clear cell output in code

Using the clear_output() gives makes your Notebook have the jitters, though. I recommend using the display() function as well, like this (Python 2.7):

from random import uniform import time from IPython.display import display, clear_output  def black_box(): i = 1 while True:     clear_output(wait=True)     display('Iteration '+str(i)+' Score: '+str(uniform(0, 1)))     time.sleep(1)     i += 1 

Answer 2

The usual (documented) way to do what you describe (that only works with Python 3) is:

print('Iteration', i, 'Score:', uniform(0, 1), end='\r') 

In Python 2 we have to sys.stdout.flush() after the print, as it shows in this answer:

print('Iteration', i, 'Score:', uniform(0, 1), end='\r') sys.stdout.flush() 

Using IPython notebook I had to concatenate the string to make it work:

print('Iteration ' + str(i) + ', Score: ' + str(uniform(0, 1)), end='\r') 

And finally, to make it work with Jupyter, I used this:

print('\r', 'Iteration', i, 'Score:', uniform(0, 1), end='') 

Or you could split the prints before and after the time.sleep if it makes more sense, or you need to be more explicit:

print('Iteration', i, 'Score:', uniform(0, 1), end='') time.sleep(1) print('', end='\r') # or even print('\r', end='')