57 – Underscore in the REPL

57 – Underscore in the REPL#

When working in the REPL, the result of the last non-None expression is saved in the special variable _ (underscore).

This is especially useful if you run a slow piece of code and forget to assign the result. Just do result = _.

As someone who uses the REPL a lot, I find this to be very helpful!

Here is an example REPL session showcasing this feature:

>>> 3 ** 3 ** 3
7625597484987
>>> print(_)
7625597484987

>>> _
7625597484987

>>> sum([_, _, -_, -_])
0
>>> _
0

Note that functions that return None do not update the value stored in _.