Python Shell - Grab last expression output and put back into variable. An Underscore Tip

Excuse if this is obvious to Python programmers but for those crossing over from ObjectScript this may be a useful tip.

The scenario is developing some Embedded python commands.

Testing out functionality is being confirmed via the shell:

$SYSTEM.Python.Shell()
 
Python 3.9.5 (default, Mar 14 2023, 06:58:44) [MSC v.1927 64 bit (AMD64)] on win32
Type quit() or Ctrl-D to exit this shell.
>>>

When Python evaluates an expression in the shell, it prints the result of the expression to the terminal.

>>> 1 + 2

3

It is quite easy to accidentally evaluate and print out values

>>> iris.cls("%Dictionary.MethodDefinition")._OpenId("%Library.String||LogicalToJSON",0)
<iris.%Dictionary.MethodDefinition object at 0x000001C55C8572D0>
# .. but I really wanted that object for further work

ie: What I really wanted to do was set a new variable to return value from that function call:

>>> myvar = iris.cls("%Dictionary.MethodDefinition")._OpenId("%Library.String||LogicalToJSON",0)

This can cause delay if there was a lot of setup involved to get to this point.

To the rescue is Hero variable "_" underscore. This holds the value of last evaluated expression for you.

You can save you R&D moment by executing: "[variable name] = _  "

>>> iris.cls("%Dictionary.MethodDefinition")._OpenId("%Library.String||LogicalToJSON",0)
<iris.%Dictionary.MethodDefinition object at 0x000001C55C8572D0>
# oops

>>> myvar = _

# Keep calm and carry on ...

>>> myvar._ClassName()

'MethodDefinition

Hope this is useful for someone else.