scatter_matrix in pandas returns lots of text - how to remove it?

The scatter_matrix function returns the array of axes it generates, in case you want to modify them.

In an interactive Python console (IPython, the last line of an IPython notebook cell, etc.), return values (apart from None) are printed to the console (or the output of the cell, respectively), to it easier to see what is going on. If you were to run scatter_matrix as part of a script, this would not be printed, it would just be thrown away.

If you assign the return value to a variable

axes = scatter_matrix(...)

you get no output. The same applies in IPython (including notebooks, not in vanilla python with the >>> prompt) when you execute an empty statement after the the calculation – which is what adding ; to the end of the line does

scatter_matrix(...);

there is no return value to be echoed, so there is not output.

Compare

In[1]: 5
Out[1]: 5

In[2]: x=5

In[3]: 5;

In[4]: 5; 6
Out[4]: 6

Thanks to @IanS. Of course, a ; at the end of the line works.