Include lines in tangled source code but not in executed code block

Question

The title might be slightly confusing. What I mean is this. Let's say I have a code block which has some error checking code. If there is an error, the (tangled) program should not continue past that point. Let's say I work with python. If I have a source code like this

if len(dummy_list) == 0:
  print("Error!!!")
  sys.exit(0)

Executing this in a code block makes EMACS hang. So I don't want this line to be executed in my source block. But I want this line to be present in the tangled source code. Moreover, it would be great if there was a way to destroy the current running session when I counter an error. Is there a way to achieve this?

Answer 1

You can set the error checking code in a separate code block with headers set to something like

:tangle myfile.py :eval never

This works because code blocks with the same :tangle path are concatenated sequentially into the resulting file. If you are running your Python code in python or ipython sessions then the evaluations should work even though they are in multiple code blocks.