python-shell.py

import itertools


def get_user_input():

	for i in itertools.count():
		try:
			yield i, input('In [%d]: ' % i)
		except KeyboardInterrupt:
			pass
		except EOFError:
			break


def exec_function(user_input):

	try:
		compile(user_input, '<stdin>', 'eval')
	except SyntaxError:
		return exec
	return eval


def exec_user_input(i, user_input, user_globals):

	user_globals = user_globals.copy()
	try:
		retval = exec_function(user_input)(
			user_input, user_globals
		)
	except Exception as e:
		print('%s: %s' % (e.__class__.__name__, e))
	else:
		if retval is not None:
			print('Out [%d]: %s' % (i, retval))
	return user_globals


def selected_user_globals(user_globals):

	return (
		(key, user_globals[key])
		for key in sorted(user_globals)
		if not key.startswith('__') or not key.endswith('__')
	)


def save_user_globals(user_globals, path='user_globals.txt'):

	with open(path, 'w') as fd:
		for key, val in selected_user_globals(user_globals):
			fd.write('%s = %s (%s)\n' % (
				key, val, val.__class__.__name__
			))


def main():

	user_globals = {}
	save_user_globals(user_globals)
	for i, user_input in get_user_input():
		user_globals = exec_user_input(
			i, user_input, user_globals
		)
		save_user_globals(user_globals)


if __name__ == '__main__':
	main()