Python interactive REPL inside a with statement

Question

From an python interactive session, is there a way to enter a REPL loop inside a with statement?

Normally, a with statement is executed as a single block

>>>
>>> with app.app_context():
>>> ...   # Normally this is executed as a single block, all at once

I'd like to be able to run code in an interactive session, in the context.

>>>
>>> with app.app_context():
>>> # do stuff here in a REPL loop

Is this in a script that you want to temporarily turn interactive, or are you already in an interactive session, where you want to run statements in a `with` context interactively without needing to finish the whole `with` block first? — user2357112, Apr 08 '16 at 22:32
@PadraicCunningham REPL = Read Eval Print Loop https://en.wikipedia.org/wiki/Read%E2%80%93eval%E2%80%93print_loop — 00500005, Apr 08 '16 at 22:38
@00500005, I know what a repl is, I meant in the context of your question — Padraic Cunningham, Apr 08 '16 at 22:39

score 7 · Accepted Answer · answered Apr 08 '16 at 22:34

7

You can't exactly mimic a with statement, but you can probably get close by calling app.app_context().__enter__() manually.

This won't __exit__ automatically if there's an exception, but otherwise it should work the same (you might need to call __exit__ yourself when you're done, I'm not sure what exactly that context manager does).

answered Apr 08 '16 at 22:34

Blckknght

100,903
11
120
169

A context manager calls `__exit__` for any exit condition, and can do things like recover or change exceptions. But for my purposes, that's not that useful – 00500005 Apr 08 '16 at 22:38
Yeah, that's why I mentioned calling `__exit__` yourself. It might not matter though, depending on what the `app_context` context manager does (its `__exit__` method may do little or nothing). – Blckknght Apr 08 '16 at 22:44

Akshat Mahajan · Answer 2 · 2016-04-08T22:50:33.933

A fully-functioning REPL for very simple inputs (i.e. no variable declarations) with a contextmanager in Python 2.7:

from contextlib import contextmanager
import sys 
class app(object):
    @contextmanager
    def app_context(self):
       sys.stdout.write(">>> ")
       yield raw_input()

with app().app_context() as output:
   while True:
       print eval(output)
       output = app().app_context().__enter__()

This will need some work to handle anything more sophisticated - that eval is an eyesore, and there's no good way to break the loop short of ^C - but it should work.

Python interactive REPL inside a with statement

2 Answers2