txautoreload.py

"""
Restarts the application if any file changed.
Borrowed from Tornado and Django.

Usage:
    import txautoreload
    txautoreload.start()
"""
import types
import os
import sys

from twisted.internet import reactor, task
from twisted.python import log

__all__ = ['start']

RELOAD_ATTEMPTED = False
WIN32 = sys.platform == 'win32'

def start(clock=None, check_time=0.5):
    """Restarts the process automatically when a module is modified"""
    clock = clock or reactor
    modify_times = {}
    scheduler = task.LoopingCall(reload_on_update, clock, modify_times)
    scheduler.clock = clock
    scheduler.start(check_time)

def reload_on_update(clock, modify_times):
    global RELOAD_ATTEMPTED
    if RELOAD_ATTEMPTED:
        # We already tried to reload and it didn't work, so don't try again.
        return

    changed, path = code_changed(modify_times)
    if changed:
        _reload_attempted = True
        log.msg("%s modified; restarting application" % path)
        clock.stop()
        try:
            os.execv(sys.executable, [sys.executable] + sys.argv)
        except OSError, e:
            # Mac OS X versions prior to 10.6 do not support execv in a
            # process that contains multiple threads. Instead of
            # re-executing in the current process, start a new one and
            # cause the current process to exit. This isn't ideal since
            # new process is detached from the parent terminal and thus
            # cannot easily be killed with ctrl-C, but it's better than
            # not being able to autoreload at all.
            # Unfortunately the errno returned in this case does not apper
            # to be consistent, so we can't easily check for this error
            # specifically.
            os.spawnv(os.P_NOWAIT, sys.executable, [sys.executable] + sys.argv)
            sys.exit(0)

def code_changed(modify_times):
    # Some modules play games with sys.modules (e.g. email/__init__.py
    # in the standard library), and occasionally this can cause strange
    # failures in getattr. Just ignore anything that's not and ordinary
    # module.
    for module in sys.modules.values():
        if not isinstance(module, types.ModuleType):
            continue

        path = getattr(module, "__file__", None)
        if not path:
            continue

        if path.endswith(".pyc") or path.endswith(".pyo"):
            path = path[:-1]

        try:
            stat = os.stat(path)
        except:
            # e.g. TypeError
            continue

        modified = stat.st_mtime
        if WIN32:
            modified -= stat.st_ctime

        if not path in modify_times:
            modify_times[path] = modified
            continue

        if modified != modify_times[path]:
            return True, path

    return False, None