#$save macro does not work in many cases

[Almenon]

Currently I use deepcopy to save the state: https://docs.python.org/3.6/library/copy.html#copy.deepcopy

This means the types must be serializable by deepcopy, which unfortunately has some major limitations:

• Deepcopy cannot handle the following types:

"This module does not copy types like module, method, stack trace, stack frame, file, socket, window, array, or any similar types"

• Imports are not saved (although you can still use imports in the saved section, the import will just happen twice)

• Conditional imports and imports in functions may not work

• File I/O does not work (TextIOWrapper is not serializable)

Please comment below if you run into any issues with #$save

[Almenon]

another example in which save fails:

from urllib.request import urlopen
import json

data = urlopen("https://api.github.com/")

#$save
# error result: TypeError: cannot serialize '_io.BufferedReader' object 

[Almenon]

Ideas to fix problem:

A. define deepcopy() method on the uncopyable object to make it copyable. downside: who knows what object the user will be using? This solution would have to be manually implemented for certain types

B. Use deepcopy differently. Maybe there's some sort of argument I can pass in? Answer: no

C. Define my own deepcopy. See links 1, 2, and 3. Also the source code for the deepcopy

D. use copyreg?

E. freeze the thread and fork the process from the save point. This has the great benefit of me not having to worry about the users variables at all.

Some guy w/ similar problem: pyinvoke/invoke#421