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"""
Config.py
February 13, 2011
Reads and writes config files in a simple (key = value) or just (key) for boolean
properties, and notifies listeners when the values are changed.
"""
import errno
import logging
import os
from threading import Lock
logger = logging.getLogger("Config")
class Config(object):
"""A config file"""
def __init__(self, path):
self._path = os.path.expanduser(path)
self._options = {}
self._listeners = {}
self._lock = Lock()
self.load()
def __contains__(self, key):
"""Returns true if this config has the given key."""
return key in self._options
def __iter__(self):
"""Returns an iterator over the keys of this Config object."""
return iter(self._options)
def load(self):
"""Loads a config file, if it exists."""
try:
f = open(self._path, "r")
except:
logger.warning("Failed to open config file: {0}".format(self._path))
self._options = {}
return
try:
for line in f:
item = line.split("=", 1)
if len(item) == 1:
key = item[0].strip()
self._options[key] = True
else:
key = item[0].strip()
value = item[1].strip()
self._options[key] = value
except:
logger.warning("Error reading config file: {0}".format(self._path))
self._options = {}
def save(self):
"""Saves the config file, creating the destination directory if necessary."""
# Create the destination directory
dirname = os.path.dirname(self._path)
try:
os.makedirs(dirname, 0700)
except os.error, e:
if e.errno != errno.EEXIST:
logger.error("Failed to create directory: {0}".format(dirname))
return
with open(self._path, "w") as f:
for key, value in self._options.items():
f.write("{0} = {1}\n".format(key, value))
def add_listener(self, key, callback):
"""Adds a listener to notify the given callback when the given key is changed.
Callbacks should be of the form f(key, value)."""
if key in self._listeners:
self._listeners[key].append(callback)
else:
self._listeners[key] = [callback]
def notify_all(self):
"""Notifies all listeners of the current value for each key they are watching."""
for key in self._listeners:
if key in self._options:
value = self._options[key]
for f in self._listeners[key]:
f(key, value)
def get(self, key, default = ""):
"""Returns the value of the given key, or the default value."""
if key in self._options:
return self._options[key]
else:
return default
def get_bool(self, key, default = False):
"""Returns the value of the given key as a boolean, or the default value if it fails
to convert or does not exist."""
if key not in self._options:
return default
value = self._options[key]
if value == True or value == "True":
return True
elif value == False or value == "False":
return False
else:
return default
def get_int(self, key, default = 0):
"""Returns this value of the given key as an int, or the default value if it fails to
convert or does not exist."""
if key not in self._options:
return default
value = self._options[key]
try:
return int(value)
except:
return default
def set(self, key, value):
"""Sets the value for the given key, saves the config file and notifies any
listeners that the value has changed."""
with self._lock:
self._options[key] = value
self.save()
if key in self._listeners:
for f in self._listeners[key]:
f(key, value)
def set_if_unset(self, key, value):
"""Calls set(key, value) only if the key does not exist in this config."""
if key not in self._options:
self.set(key, value)
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