Use The Underscore in The REPL

You can obtain the result of the last expression in a Python REPL with the underscore operator, e.g. in the Python REPL this looks like:

>>> 3 * 3
9
>>> _ + 3
12

This works in the IPython shell too. In addition, the IPython shell allows you to use Out[n] to get the value of the expression In[n]. E.g., Out[1] would give us the number 9 in the example below:

In [1]: 3 * 3
Out[1]: 9

In [2]: Out[1] + 3
Out[2]: 12

In [3]: _ + 3
Out[3]: 15

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