Keyboard shortcuts broken running interactive Python Console from a script

Question

You can start an interactive console from inside a script with following code:

import code

# do something here

vars = globals()
vars.update(locals())
shell = code.InteractiveConsole(vars)
shell.interact()

When I run the script like so:

$ python my_script.py

an interactive console opens:

Python 2.7.2+ (default, Jul 20 2012, 22:12:53) 
[GCC 4.6.1] on linux2
Type "help", "copyright", "credits" or "license" for more information.
(InteractiveConsole)
>>>

The console has all globals and locals loaded which is great since I can test stuff easily.

The problem here is that arrows don't work as they normally do when starting an Python console. They simply display escaped characters to the console:

>>> ^[[A^[[B^[[C^[[D

This means that I can't recall previous commands using the up/down arrow keys and I can't edit the lines with the left/right arrow keys either.

Does anyone know why is that and/or how to avoid that?

Answer 1

Check out readline and rlcompleter:

import code
import readline
import rlcompleter

# do something here

vars = globals()
vars.update(locals())
readline.set_completer(rlcompleter.Completer(vars).complete)
readline.parse_and_bind("tab: complete")
shell = code.InteractiveConsole(vars)
shell.interact()

Answer 2

This is the one I use:

def debug_breakpoint():
    """
    Python debug breakpoint.
    """
    from code import InteractiveConsole
    from inspect import currentframe
    try:
        import readline # noqa
    except ImportError:
        pass

    caller = currentframe().f_back

    env = {}
    env.update(caller.f_globals)
    env.update(caller.f_locals)

    shell = InteractiveConsole(env)
    shell.interact(
        '* Break: {} ::: Line {}\n'
        '* Continue with Ctrl+D...'.format(
            caller.f_code.co_filename, caller.f_lineno
        )
    )

For example, consider the following script:

a = 10
b = 20
c = 'Hello'

debug_breakpoint()

a = 20
b = c
c = a

mylist = [a, b, c]

debug_breakpoint()


def bar():
    a = '1_one'
    b = '2+2'
    debug_breakpoint()

bar()

When executed, this file shows to following behavior:

$ python test_debug.py
* Break: test_debug.py ::: Line 24
* Continue with Ctrl+D...
>>> a
10
>>>
* Break: test_debug.py ::: Line 32
* Continue with Ctrl+D...
>>> b
'Hello'
>>> mylist
[20, 'Hello', 20]
>>> mylist.append(a)
>>>
* Break: test_debug.py ::: Line 38
* Continue with Ctrl+D...
>>> a
'1_one'
>>> mylist
[20, 'Hello', 20, 20]