dynamic scope like in the good old days

stack_search.py

import sys
import pdb
import types

__doc__ = """

This example shows how to search back through the stack
for a local and return a reference to calling function.

Useful hack for when you are deep in the hierarchy and
need something the n-th calling function has w/o having
to make a global.


"""


class Log:
    def msg(self, alert, msg):
        if alert:
            print "**", msg, "**"
        else:
            print msg


def stack_search(name, _type=None):
    "locals for a locals <name> of optional type <_type>"
    try:
        i = 0
        while True:
            frame = sys._getframe(i)
            if name in frame.f_locals:
                if _type != None:
                    o = frame.f_locals[name]
                    if type(o) == _type:
                        return o
                else:
                    return frame.f_locals[name]
            i += 1
    except ValueError:
        return None


def one():
    l = Log()
    l.msg(True, "calling two()")
    two()


def two():
    three()


def three():
    four()


def four():
    logger = stack_search('l', types.InstanceType)
    if logger:
        logger.msg(True, "sending a message from way down here!")


one()