import contextlib
import textwrap
from functools import wraps
__all__ = ["Settings"]
[docs]class Settings(dict):
"""Automatic multi-level dictionary. Subclass of built-in class :class:`dict`.
The shortcut dot notation (``s.basis`` instead of ``s['basis']``) can be used for keys that:
* are strings
* don't contain whitespaces
* begin with a letter or an underscore
* don't both begin and end with two or more underscores.
Iteration follows lexicographical order (via :func:`sorted` function)
Methods for displaying content (:meth:`~object.__str__` and :meth:`~object.__repr__`) are overridden to recursively show nested instances in easy-readable format.
Regular dictionaries (also multi-level ones) used as values (or passed to the constructor) are automatically transformed to |Settings| instances::
>>> s = Settings({'a': {1: 'a1', 2: 'a2'}, 'b': {1: 'b1', 2: 'b2'}})
>>> s.a[3] = {'x': {12: 'q', 34: 'w'}, 'y': 7}
>>> print(s)
a:
1: a1
2: a2
3:
x:
12: q
34: w
y: 7
b:
1: b1
2: b2
"""
[docs] def __init__(self, *args, **kwargs):
dict.__init__(self, *args, **kwargs)
cls = type(self)
for k, v in self.items():
if isinstance(v, dict) and type(v) is not cls:
self[k] = cls(v)
if isinstance(v, list):
self[k] = [cls(i) if (isinstance(i, dict) and type(i) is not cls) else i for i in v]
[docs] def copy(self):
"""Return a new instance that is a copy of this one. Nested |Settings| instances are copied recursively, not linked.
In practice this method works as a shallow copy: all "proper values" (leaf nodes) in the returned copy point to the same objects as the original instance (unless they are immutable, like ``int`` or ``tuple``). However, nested |Settings| instances (internal nodes) are copied in a deep-copy fashion. In other words, copying a |Settings| instance creates a brand new "tree skeleton" and populates its leaf nodes with values taken directly from the original instance.
This behavior is illustrated by the following example::
>>> s = Settings()
>>> s.a = 'string'
>>> s.b = ['l','i','s','t']
>>> s.x.y = 12
>>> s.x.z = {'s','e','t'}
>>> c = s.copy()
>>> s.a += 'word'
>>> s.b += [3]
>>> s.x.u = 'new'
>>> s.x.y += 10
>>> s.x.z.add(1)
>>> print(c)
a: string
b: ['l', 'i', 's', 't', 3]
x:
y: 12
z: set([1, 's', 'e', 't'])
>>> print(s)
a: stringword
b: ['l', 'i', 's', 't', 3]
x:
u: new
y: 22
z: set([1, 's', 'e', 't'])
This method is also used when :func:`python3:copy.copy` is called.
"""
cls = type(self)
ret = cls()
for name in self:
if isinstance(self[name], Settings):
ret[name] = self[name].copy()
else:
ret[name] = self[name]
return ret
[docs] def soft_update(self, other):
"""Update this instance with data from *other*, but do not overwrite existing keys. Nested |Settings| instances are soft-updated recursively.
In the following example ``s`` and ``o`` are previously prepared |Settings| instances::
>>> print(s)
a: AA
b: BB
x:
y1: XY1
y2: XY2
>>> print(o)
a: O_AA
c: O_CC
x:
y1: O_XY1
y3: O_XY3
>>> s.soft_update(o)
>>> print(s)
a: AA #original value s.a not overwritten by o.a
b: BB
c: O_CC
x:
y1: XY1 #original value s.x.y1 not overwritten by o.x.y1
y2: XY2
y3: O_XY3
*Other* can also be a regular dictionary. Of course in that case only top level keys are updated.
Shortcut ``A += B`` can be used instead of ``A.soft_update(B)``.
"""
for name in other:
if isinstance(other[name], Settings):
if name not in self:
self[name] = other[name].copy()
elif isinstance(self[name], Settings):
self[name].soft_update(other[name])
elif name not in self:
self[name] = other[name]
return self
[docs] def update(self, other):
"""Update this instance with data from *other*, overwriting existing keys. Nested |Settings| instances are updated recursively.
In the following example ``s`` and ``o`` are previously prepared |Settings| instances::
>>> print(s)
a: AA
b: BB
x:
y1: XY1
y2: XY2
>>> print(o)
a: O_AA
c: O_CC
x:
y1: O_XY1
y3: O_XY3
>>> s.update(o)
>>> print(s)
a: O_AA #original value s.a overwritten by o.a
b: BB
c: O_CC
x:
y1: O_XY1 #original value s.x.y1 overwritten by o.x.y1
y2: XY2
y3: O_XY3
*Other* can also be a regular dictionary. Of course in that case only top level keys are updated.
"""
for name in other:
if isinstance(other[name], Settings):
if name not in self or not isinstance(self[name], Settings):
self[name] = other[name].copy()
else:
self[name].update(other[name])
else:
self[name] = other[name]
[docs] def merge(self, other):
"""Return new instance of |Settings| that is a copy of this instance soft-updated with *other*.
Shortcut ``A + B`` can be used instead of ``A.merge(B)``.
"""
ret = self.copy()
ret.soft_update(other)
return ret
[docs] def find_case(self, key):
"""Check if this instance contains a key consisting of the same letters as *key*, but possibly with different case. If found, return such a key. If not, return *key*."""
if not isinstance(key, str):
return key
lowkey = key.lower()
for k in self:
try:
if k.lower() == lowkey:
return k
except (AttributeError, TypeError):
pass
return key
[docs] def get(self, key, default=None):
"""Like regular ``get``, but ignore the case."""
return dict.get(self, self.find_case(key), default)
[docs] def pop(self, key, *args):
"""Like regular ``pop``, but ignore the case."""
# A single positional argument can be supplied `*args`,
# functioning as a default return value in case `key` is not present in this instance
return dict.pop(self, self.find_case(key), *args)
[docs] def popitem(self, key):
"""Like regular ``popitem``, but ignore the case."""
return dict.popitem(self, self.find_case(key))
[docs] def setdefault(self, key, default=None):
"""Like regular ``setdefault``, but ignore the case and if the value is a dict, convert it to |Settings|."""
cls = type(self)
if isinstance(default, dict) and type(default) is not cls:
default = cls(default)
return dict.setdefault(self, self.find_case(key), default)
[docs] def as_dict(self):
"""Return a copy of this instance with all |Settings| replaced by regular Python dictionaries."""
d = {}
for k, v in self.items():
if isinstance(v, Settings):
d[k] = v.as_dict()
elif isinstance(v, list):
d[k] = [i.as_dict() if isinstance(i, Settings) else i for i in v]
else:
d[k] = v
return d
[docs] @classmethod
def suppress_missing(cls):
"""A context manager for temporary disabling the :meth:`.Settings.__missing__` magic method: all calls now raising a :exc:`KeyError`.
As a results, attempting to access keys absent from an arbitrary |Settings| instance will raise a :exc:`KeyError`, thus reverting to the default dictionary behaviour.
.. note::
The :meth:`.Settings.__missing__` method is (temporary) suppressed at the class level to ensure consistent invocation by the Python interpreter.
See also `special method lookup`_.
Example:
.. code:: python
>>> s = Settings()
>>> with s.suppress_missing():
... s.a.b.c = True
KeyError: 'a'
>>> s.a.b.c = True
>>> print(s.a.b.c)
True
.. _`special method lookup`: https://docs.python.org/3/reference/datamodel.html#special-method-lookup
"""
return SuppressMissing(cls)
[docs] def get_nested(self, key_tuple, suppress_missing=False):
"""Retrieve a nested value by, recursively, iterating through this instance using the keys in *key_tuple*.
The :meth:`.Settings.__getitem__` method is called recursively on this instance until all keys in key_tuple are exhausted.
Setting *suppress_missing* to ``True`` will internally open the :meth:`.Settings.suppress_missing` context manager, thus raising a :exc:`KeyError` if a key in *key_tuple* is absent from this instance.
.. code:: python
>>> s = Settings()
>>> s.a.b.c = True
>>> value = s.get_nested(('a', 'b', 'c'))
>>> print(value)
True
"""
s = self
with contextlib.suppress() if not suppress_missing else s.suppress_missing():
for k in key_tuple:
s = s[k]
return s
[docs] def set_nested(self, key_tuple, value, suppress_missing=False):
"""Set a nested value by, recursively, iterating through this instance using the keys in *key_tuple*.
The :meth:`.Settings.__getitem__` method is called recursively on this instance, followed by :meth:`.Settings.__setitem__`, until all keys in key_tuple are exhausted.
Setting *suppress_missing* to ``True`` will internally open the :meth:`.Settings.suppress_missing` context manager, thus raising a :exc:`KeyError` if a key in *key_tuple* is absent from this instance.
.. code:: python
>>> s = Settings()
>>> s.set_nested(('a', 'b', 'c'), True)
>>> print(s)
a:
b:
c: True
"""
s = self
with contextlib.suppress() if not suppress_missing else s.suppress_missing():
for k in key_tuple[:-1]:
s = s[k]
s[key_tuple[-1]] = value
[docs] def flatten(self, flatten_list=True):
"""Return a flattened copy of this instance.
New keys are constructed by concatenating the (nested) keys of this instance into tuples.
Opposite of the :meth:`.Settings.unflatten` method.
If *flatten_list* is ``True``, all nested lists will be flattened as well. Dictionary keys are replaced with list indices in such case.
.. code-block:: python
>>> s = Settings()
>>> s.a.b.c = True
>>> print(s)
a:
b:
c: True
>>> s_flat = s.flatten()
>>> print(s_flat)
('a', 'b', 'c'): True
"""
if flatten_list:
nested_type = (Settings, list)
iter_type = lambda x: x.items() if isinstance(x, Settings) else enumerate(x)
else:
nested_type = Settings
iter_type = Settings.items
def _concatenate(key_ret, sequence):
# Switch from Settings.items() to enumerate() if a list is encountered
for k, v in iter_type(sequence):
k = key_ret + (k,)
if isinstance(v, nested_type) and v: # Empty lists or Settings instances will return ``False``
_concatenate(k, v)
else:
ret[k] = v
# Changes keys into tuples
cls = type(self)
ret = cls()
_concatenate((), self)
return ret
[docs] def unflatten(self, unflatten_list=True):
"""Return a nested copy of this instance.
New keys are constructed by expanding the keys of this instance (*e.g.* tuples) into new nested |Settings| instances.
If *unflatten_list* is ``True``, integers will be interpretted as list indices and are used for creating nested lists.
Opposite of the :meth:`.Settings.flatten` method.
.. code-block:: python
>>> s = Settings()
>>> s[('a', 'b', 'c')] = True
>>> print(s)
('a', 'b', 'c'): True
>>> s_nested = s.unflatten()
>>> print(s_nested)
a:
b:
c: True
"""
cls = type(self)
ret = cls()
for key, value in self.items():
s = ret
for k1, k2 in zip(key[:-1], key[1:]):
if not unflatten_list:
s = s[k1]
continue
if isinstance(k2, int) and not isinstance(s[k1], list):
s[k1] = []
if isinstance(k1, int): # Apply padding to s
s += [Settings()] * (k1 - len(s) + 1)
s = s[k1]
s[key[-1]] = value
return ret
# =======================================================================
[docs] def __iter__(self):
"""Iteration through keys follows lexicographical order. All keys are sorted as if they were strings."""
return iter(sorted(self.keys(), key=str))
[docs] def __missing__(self, name):
"""When requested key is not present, add it with an empty |Settings| instance as a value.
This method is essential for automatic insertions in deeper levels. Without it things like::
>>> s = Settings()
>>> s.a.b.c = 12
will not work.
The behaviour of this method can be suppressed by initializing the :class:`.Settings.suppress_missing` context manager.
"""
cls = type(self)
self[name] = cls()
return self[name]
[docs] def __contains__(self, name):
"""Like regular ``__contains`__``, but ignore the case."""
return dict.__contains__(self, self.find_case(name))
[docs] def __getitem__(self, name):
"""Like regular ``__getitem__``, but ignore the case."""
return dict.__getitem__(self, self.find_case(name))
[docs] def __setitem__(self, name, value):
"""Like regular ``__setitem__``, but ignore the case and if the value is a dict, convert it to |Settings|."""
cls = type(self)
if isinstance(value, dict) and type(value) is not cls:
value = cls(value)
dict.__setitem__(self, self.find_case(name), value)
[docs] def __delitem__(self, name):
"""Like regular ``__detitem__``, but ignore the case."""
return dict.__delitem__(self, self.find_case(name))
[docs] def __getattr__(self, name):
"""If name is not a magic method, redirect it to ``__getitem__``."""
if name.startswith("__") and name.endswith("__"):
return dict.__getattribute__(self, name)
return self[name]
[docs] def __setattr__(self, name, value):
"""If name is not a magic method, redirect it to ``__setitem__``."""
if name.startswith("__") and name.endswith("__"):
dict.__setattr__(self, name, value)
else:
self[name] = value
[docs] def __delattr__(self, name):
"""If name is not a magic method, redirect it to ``__delitem__``."""
if name.startswith("__") and name.endswith("__"):
dict.__delattr__(self, name)
else:
del self[name]
[docs] def _str(self, indent):
"""Print contents with *indent* spaces of indentation. Recursively used for printing nested |Settings| instances with proper indentation."""
ret = ""
for key, value in self.items():
ret += " " * indent + str(key) + ": \t"
if isinstance(value, Settings):
if len(value) == 0:
ret += "<empty Settings>\n"
else:
ret += "\n" + value._str(indent + len(str(key)) + 1)
else: # Apply consistent indentation at every '\n' character
indent_str = " " * (2 + indent + len(str(key))) + "\t"
ret += textwrap.indent(str(value), indent_str)[len(indent_str) :] + "\n"
return ret if ret else "<empty Settings>"
[docs] def __str__(self):
return self._str(0)
__repr__ = __str__
__iadd__ = soft_update
__add__ = merge
__copy__ = copy
class SuppressMissing(contextlib.AbstractContextManager):
"""A context manager for temporary disabling the :meth:`.Settings.__missing__` magic method. See :meth:`Settings.suppress_missing` for more details."""
def __init__(self, obj: type):
"""Initialize the :class:`SuppressMissing` context manager."""
# Ensure that obj is a class, not a class instance
self.obj = obj if isinstance(obj, type) else type(obj)
self.missing = obj.__missing__
def __enter__(self):
"""Enter the :class:`SuppressMissing` context manager: delete :meth:`.Settings.__missing__` at the class level."""
@wraps(self.missing)
def __missing__(self, name):
raise KeyError(name)
# The __missing__ method is replaced for as long as the context manager is open
setattr(self.obj, "__missing__", __missing__)
def __exit__(self, exc_type, exc_value, traceback):
"""Exit the :class:`SuppressMissing` context manager: reenable :meth:`.Settings.__missing__` at the class level."""
setattr(self.obj, "__missing__", self.missing)
