How to hide <matplotlib.lines.Line2D> in IPython notebook

You can use a semi-colon ; to end the line. This suppresses the unwanted output when generating plots:

plt.plot(I,'o');

In general, using a semi-colon stops IPython from printing any output value from that line of a code block. For example, the executing the cell containing the code 1+1; would not output 2.

An alternative way would be to bind a variable to the plot:

_ = plt.plot(a)

This way, IPython only shows you the plots and the name _ is bound to the unwanted output.

Another way is to just write plt.show() at the end of your drawing code. It would take less symbols to type if you're generating many subplots and/or drawing many plots on a single subplot.