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utils.py
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utils.py
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# -*- coding: utf-8 -*-
import importlib
import inspect
import logging
import threading
import types
from collections import deque, defaultdict
import tornado.gen
import frozendict
from .settings import check_protected, check_override
from . import lang
__all__ = ['AttributesDict']
protected = lang.protected(check=check_protected) # pylint: disable=invalid-name
override = lang.override(check=check_override) # pylint: disable=invalid-name
_LOGGER = logging.getLogger(__name__)
class EventHelper:
def __init__(self, listener_type):
assert listener_type is not None, 'Must provide valid listener type'
self._listener_type = listener_type
self._listeners = set()
def add_listener(self, listener):
assert isinstance(listener, self._listener_type), 'Listener is not of right type'
self._listeners.add(listener)
def remove_listener(self, listener):
self._listeners.discard(listener)
def remove_all_listeners(self):
self._listeners.clear()
@property
def listeners(self):
return self._listeners
def fire_event(self, event_function, *args, **kwargs):
if event_function is None:
raise ValueError('Must provide valid event method')
# Make a copy of the list for iteration just in case it changes in a callback
for listener in list(self.listeners):
try:
getattr(listener, event_function.__name__)(*args, **kwargs)
except Exception as exception: # pylint: disable=broad-except
_LOGGER.error("Listener '%s' produced an exception:\n%s", listener, exception)
class ListenContext:
"""
A context manager for listening to producer that can generate messages.
The requirements for the producer are that it has methods:
* start_listening(..), and,
* stop_listening(..)
and that these methods take zero or more arguments that identify the
listener and perhaps what it wants to listen to if this make sense for
the producer/listener combination.
A typical usage would be:
with ListenContext(producer, listener):
# Producer generates messages that the listener gets
pass
"""
def __init__(self, producer, *args, **kwargs):
self._producer = producer
self._args = args
self._kwargs = kwargs
def __enter__(self):
self._producer.add_listener(*self._args, **self._kwargs)
return self
def __exit__(self, exc_type, exc_value, exc_traceback):
self._producer.remove_listener(*self._args, **self._kwargs)
class ThreadSafeCounter:
def __init__(self):
self.lock = threading.Lock()
self.counter = 0
def increment(self):
with self.lock:
self.counter += 1
def decrement(self):
with self.lock:
self.counter -= 1
@property
def value(self):
with self.lock:
return self.counter
class AttributesFrozendict(frozendict.frozendict):
def __init__(self, *args, **kwargs):
super().__init__(*args, **kwargs)
self._initialised = True
def __getattr__(self, attr):
"""
Read a key as an attribute. Raise AttributeError on missing key.
Called only for attributes that do not exist.
"""
# This attribute is looked for by pickle when deserialising. At this point
# the object is not yet constructed and so accessing any members is
# dangerous and often causes infinite recursion so I have to guard like this.
if attr == '__setstate__':
raise AttributeError()
try:
return self[attr]
except KeyError:
errmsg = "'{}' object has no attribute '{}'".format(self.__class__.__name__, attr)
raise AttributeError(errmsg)
def __dir__(self):
"""
So we get tab completion.
:return: The keys of the dict
"""
return list(self.keys())
class AttributesDict(types.SimpleNamespace):
def __setitem__(self, key, value):
setattr(self, key, value)
def __getitem__(self, item):
try:
return getattr(self, item)
except AttributeError:
raise KeyError("No key '{}'".format(item))
def __delitem__(self, item):
return delattr(self, item)
def setdefault(self, key, value):
return self.__dict__.setdefault(key, value)
def get(self, *args, **kwargs):
return self.__dict__.get(*args, **kwargs)
def load_function(name, instance=None):
obj = load_object(name)
if inspect.ismethod(obj):
if instance is not None:
return obj.__get__(instance, instance.__class__)
return obj
if inspect.isfunction(obj):
return obj
raise ValueError("Invalid function name '{}'".format(name))
def load_object(fullname):
"""
Load a class from a string
"""
obj, remainder = load_module(fullname)
# Finally, retrieve the object
for name in remainder:
try:
obj = getattr(obj, name)
except AttributeError:
raise ValueError("Could not load object corresponding to '{}'".format(fullname))
return obj
def load_module(fullname):
parts = fullname.split('.')
# Try to find the module, working our way from the back
mod = None
remainder = deque()
for _ in range(len(parts)):
try:
mod = importlib.import_module('.'.join(parts))
break
except ImportError:
remainder.appendleft(parts.pop())
if mod is None:
raise ValueError("Could not load a module corresponding to '{}'".format(fullname))
return mod, remainder
def wrap_dict(flat_dict, separator='.'):
sub_dicts = defaultdict(dict)
res = {}
for key, value in flat_dict.items():
if separator in key:
namespace, sub_key = key.split(separator, 1)
sub_dicts[namespace][sub_key] = value
else:
res[key] = value
for namespace, sub_dict in sub_dicts.items():
res[namespace] = wrap_dict(sub_dict)
return res
def type_check(obj, expected_type):
if not isinstance(obj, expected_type):
raise TypeError("Got object of type '{}' when expecting '{}'".format(type(obj), expected_type))
def ensure_coroutine(wrapped):
if tornado.gen.is_coroutine_function(wrapped):
return wrapped
@tornado.gen.coroutine
def wrapper(*args, **kwargs):
raise tornado.gen.Return(wrapped(*args, **kwargs))
return wrapper
def is_mutable_property(cls, attribute):
"""
Determine whether the given attribute is a mutable property of cls. That is to say that
the attribute corresponds to a property whose fset attribute is not None.
:param cls: the class
:param attribute: the attribute
:returns: True if the attribute is a mutable property of cls
"""
try:
attr = getattr(cls, attribute)
except AttributeError:
return False
return isinstance(attr, property) and attr.fset is not None