Final answer:
In Python, a single underscore is often used as a throwaway variable, whereas in IPython, it also stores the result of the last statement. Additionally, IPython uses double and triple underscores to hold the second-to-last and third-to-last results, respectively.
Step-by-step explanation:
The underscore shortcuts in Python and IPython are quite useful for saving time and effort during programming and interactive sessions. In Python, the single underscore _ is often used as a throwaway variable, to indicate that part of a result is being intentionally ignored. However, in IPython, which is an interactive shell for Python, the underscore holds additional special meaning: after you execute a statement, IPython stores the result of that statement in the variable _ (single underscore) so you can use it in a subsequent operation.
Moreover, IPython also provides a few more underscore shortcuts:
- __ (double underscore) - holds the result of the second-to-last evaluation.
- ___ (triple underscore) - holds the result of the third-to-last evaluation.
These underscore variables are particularly handy when you wish to refer back to previous results without the need to assign a specific variable name to every intermediate result. Note that these variables should be used with caution as they are updated with every new command.