PEP 762 – REPL-acing the default REPL

I want a Lisp-like REPL for my Python programs that is available to the user who runs my compiled Python program (so, I want compilation as well). The user will be able to interact with my program (instead of just running the main function), change function definitions, etc. and mold the program to their specific use case while it's running.

Some things are a bit awkward, but what specifically can't you really do in a Python REPL? You can dynamically overwrite functions in an imported module, you can re-import modules with importlib, etc. I ask because my Lisp experience is limited.

Lisp REPL keeps the state of the program because it is a live image. With Python REPL you need to rerun the program to set the variables to their values.

You can create a file, example.py:

    import time
    value = "foo"
    def go():
      for i in range(10):
        print("...", i, value)
        time.sleep(3)

Then, in repl,

    import example
    import threading
    thread = threading.Thread(target=example.go)
    thread.start()

It will slowly print out messages and you can do "example.value = 'bar'" in the REPL and it will change.

it's not the same though—In Lisp, when you compile your program, a Lisp run-time is attached to it so you can either run the program normally (like any binary) or you could REPL into the program and see what the values of variables are (these values were set at compile time). This is helpful when you have a large dataset you don't want to load over and over.