Proposed Tail-Recursion for Python

idiom_current.py

def do_something():
  exited_on_a = False
  exited_on_b = False
  exited_on_c = False

  while 1:
    ...
    if some_condition:
      exited_on_a = True
      break
    ...
    if some_condition:
      exited_on_b = True
      break
    ...
    if some_condition:
      exited_on_b = True
      break
    ...

  if exited_on_a:
    ...
  if exited_on_b:
    ...
  if exited_on_c:
    ...

  ...

idiom_new.py

def do_something():
  ...
  if some_condition:
    recurse exit_a()
  ...
  if some_condition:
    recurse exit_b()
  ...
  if some_condition:
    recurse exit_c()
  ...
  recurse do_something()

def exit_a():
  ...
  recurse tail()

def exit_b():
  ...
  recurse tail()

def exit_c():
  recurse tail()

def tail():
  ...

idiom_nice_example.py

from __future__ import tail_recursion
from framework import job
import framework.message as msg

# In this framework, all messages have a response.  No data is stored in the
# response with the exception of the "init" message, which negotiates a job
# id used to associate subsequent results.

def new(init_message):
  j = job(init_message)
  j.send_and_wait(msg.reply(job.job_id))
  allowed = job.authorize()
  if not allowed:
    recurse nack(job)
  job.send_and_wait(msg.ack())
  job.start() # This starts a generator stored at job.runner
  recurse data(job)

def data(job):
  try:
    next = job.runner.next()
    job.send(msg.data(next))
    recurse data(job.runner.next())
  except StopIteration:
    recurse final(job)
  except Exception,e:
    recurse error(job,e):

def nack(job):
  job.send_and_wait(msg.error("not-acknowledged"))

def error(job,e = None):
  job.send(msg.error(e))
  recurse job.abort()

def final(job):
  job.wait_on_replies()
  job.send(msg.final())
  recurse job.done()