oneline.py .-- draft Python 3.5+ module to execute/evaluate lines of code with automatic imports

oneline.py

#!/usr/bin/env python3
# coding: utf-8
# Written by Koos Zevenhoven, after the python-ideas discussion 
# and code by 'Random832' here: 
# https://mail.python.org/pipermail//python-ideas/2016-April/039448.html

import types 
import sys
import importlib

class ImportDict(dict):
    def __init__(self, check_fun):
        self._check = check_fun
        
    def __getitem__(self, x):
        try:
            return super().__getitem__(x)
        except KeyError as e:
            if not self._check(x):
                raise
            mod = autoimport(x, e)
            self[x] = mod
            return mod
        
class ImportModule(types.ModuleType):
    def __getattr__(self, x):
        try:
            return self.__getattribute__(x)
        except AttributeError as e:
            self.__setattr__(x, None)
            return autoimport('.'.join((self.__name__, x)), e, parent = self)

def autoimport(name, exc_when_no_module, *, parent = None):
    try:
        if parent: 
            # Avoid infinite recursion by pre-creating the name binding
            setattr(parent, name, None)
        mod = importlib.import_module(name)
        mod.__class__ = ImportModule
        return mod
    except ImportError as e:
        if parent:
            delattr(parent, name) # clean up name binding
        if e.msg.startswith("No module named "):
            raise exc_when_no_module from None
        else:
            raise e from None

def isallowedmodule(name):
    # Here, one may want to check whether name is a stdlib module
    # For now, all imports are allowed
    return True

def autoimport_run(code_lines, *, 
                   check_fun = isallowedmodule, 
                   display = print):
    aidict = ImportDict(check_fun)
    for line in code_lines:
        try:
            display(eval(line, aidict))
        except SyntaxError:
            exec(line, aidict)
            
if __name__ == '__main__':
    # autoimport_run also takes a 'display' argument, which by default
    # is print, but it could also be something else. One could, for
    # instance, imagine having each element from an iterable be printed
    # on its own line. 

    autoimport_run(sys.argv[1:])