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class ConfigNamespace(object):
"""Abstract class representing the interface of Config objects.
A ConfigNamespace is a collection of names mapped to values, where
the values may be nested namespaces. Values can be accessed via
container notation - obj[key] - or via dotted notation - obj.key.
Both these access methods are equivalent.
To minimize name conflicts between namespace keys and class members,
the number of class members should be minimized, and the names of
all class members should start with an underscore.
Subclasses must implement the methods for container-like access,
and this class will automatically provide dotted access.
"""
# Methods that must be implemented by subclasses
def _getitem(self, key):
return NotImplementedError(key)
def __setitem__(self, key, value):
raise NotImplementedError(key, value)
def __delitem__(self, key):
raise NotImplementedError(key)
def __iter__(self):
return NotImplementedError()
def _new_namespace(self, name):
raise NotImplementedError(name)
def __contains__(self, key):
try:
self._getitem(key)
except KeyError:
return False
return True
# Machinery for converting dotted access into container access,
# and automatically creating new sections/namespaces.
#
# To distinguish between accesses of class members and namespace
# keys, we first call object.__getattribute__(). If that succeeds,
# the name is assumed to be a class member. Otherwise it is
# treated as a namespace key.
#
# Therefore, member variables should be defined in the class,
# not just in the __init__() function. See BasicNamespace for
# an example.
def __getitem__(self, key):
try:
return self._getitem(key)
except KeyError:
return Undefined(key, self)
def __getattr__(self, name):
try:
return self._getitem(name)
except KeyError:
if name.startswith('__') and name.endswith('__'):
raise AttributeError
return Undefined(name, self)
def __setattr__(self, name, value):
try:
object.__getattribute__(self, name)
object.__setattr__(self, name, value)
except AttributeError:
self.__setitem__(name, value)
def __delattr__(self, name):
try:
object.__getattribute__(self, name)
object.__delattr__(self, name)
except AttributeError:
self.__delitem__(name)
# During unpickling, Python checks if the class has a __setstate__
# method. But, the data dicts have not been initialised yet, which
# leads to _getitem and hence __getattr__ raising an exception. So
# we explicitly impement default __setstate__ behavior.
def __setstate__(self, state):
self.__dict__.update(state)
class Undefined(object):
"""Helper class used to hold undefined names until assignment.
This class helps create any undefined subsections when an
assignment is made to a nested value. For example, if the
statement is "cfg.a.b.c = 42", but "cfg.a.b" does not exist yet.
"""
def __init__(self, name, namespace):
object.__setattr__(self, 'name', name)
object.__setattr__(self, 'namespace', namespace)
def __setattr__(self, name, value):
obj = self.namespace._new_namespace(self.name)
obj[name] = value
def __setitem__(self, name, value):
obj = self.namespace._new_namespace(self.name)
obj[name] = value
# ---- Basic implementation of a ConfigNamespace
class BasicConfig(ConfigNamespace):
"""Represents a hierarchical collection of named values.
Values are added using dotted notation:
>>> n = BasicConfig()
>>> n.x = 7
>>> n.name.first = 'paramjit'
>>> n.name.last = 'oberoi'
...and accessed the same way, or with [...]:
>>> n.x
7
>>> n.name.first
'paramjit'
>>> n.name.last
'oberoi'
>>> n['x']
7
>>> n['name']['first']
'paramjit'
Iterating over the namespace object returns the keys:
>>> l = list(n)
>>> l.sort()
>>> l
['name', 'x']
Values can be deleted using 'del' and printed using 'print'.
>>> n.aaa = 42
>>> del n.x
>>> print(n)
aaa = 42
name.first = paramjit
name.last = oberoi
Nested namepsaces are also namespaces:
>>> isinstance(n.name, ConfigNamespace)
True
>>> print(n.name)
first = paramjit
last = oberoi
>>> sorted(list(n.name))
['first', 'last']
Finally, values can be read from a file as follows:
>>> from six import StringIO
>>> sio = StringIO('''
... # comment
... ui.height = 100
... ui.width = 150
... complexity = medium
... have_python
... data.secret.password = goodness=gracious me
... ''')
>>> n = BasicConfig()
>>> n._readfp(sio)
>>> print(n)
complexity = medium
data.secret.password = goodness=gracious me
have_python
ui.height = 100
ui.width = 150
"""
# this makes sure that __setattr__ knows this is not a namespace key
_data = None
def __init__(self):
self._data = {}
def _getitem(self, key):
return self._data[key]
def __setitem__(self, key, value):
self._data[key] = value
def __delitem__(self, key):
del self._data[key]
def __iter__(self):
return iter(self._data)
def __str__(self, prefix=''):
lines = []
keys = list(self._data.keys())
keys.sort()
for name in keys:
value = self._data[name]
if isinstance(value, ConfigNamespace):
lines.append(value.__str__(prefix='%s%s.' % (prefix,name)))
else:
if value is None:
lines.append('%s%s' % (prefix, name))
else:
lines.append('%s%s = %s' % (prefix, name, value))
return '\n'.join(lines)
def _new_namespace(self, name):
obj = BasicConfig()
self._data[name] = obj
return obj
def _readfp(self, fp):
while True:
line = fp.readline()
if not line:
break
line = line.strip()
if not line: continue
if line[0] == '#': continue
data = line.split('=', 1)
if len(data) == 1:
name = line
value = None
else:
name = data[0].strip()
value = data[1].strip()
name_components = name.split('.')
ns = self
for n in name_components[:-1]:
if n in ns:
ns = ns[n]
if not isinstance(ns, ConfigNamespace):
raise TypeError('value-namespace conflict', n)
else:
ns = ns._new_namespace(n)
ns[name_components[-1]] = value
# ---- Utility functions
def update_config(target, source):
"""Imports values from source into target.
Recursively walks the <source> ConfigNamespace and inserts values
into the <target> ConfigNamespace. For example:
>>> n = BasicConfig()
>>> n.playlist.expand_playlist = True
>>> n.ui.display_clock = True
>>> n.ui.display_qlength = True
>>> n.ui.width = 150
>>> print(n)
playlist.expand_playlist = True
ui.display_clock = True
ui.display_qlength = True
ui.width = 150
>>> from iniparse import ini
>>> i = ini.INIConfig()
>>> update_config(i, n)
>>> print(i)
[playlist]
expand_playlist = True
<BLANKLINE>
[ui]
display_clock = True
display_qlength = True
width = 150
"""
for name in sorted(source):
value = source[name]
if isinstance(value, ConfigNamespace):
if name in target:
myns = target[name]
if not isinstance(myns, ConfigNamespace):
raise TypeError('value-namespace conflict')
else:
myns = target._new_namespace(name)
update_config(myns, value)
else:
target[name] = value