# Licensed under a 3-clause BSD style license - see LICENSE.rst
"""Sundry function and class decorators."""
import functools
import inspect
import textwrap
import threading
import types
import warnings
from inspect import signature
from .exceptions import (
AstropyDeprecationWarning,
AstropyPendingDeprecationWarning,
AstropyUserWarning,
)
__all__ = [
"classproperty",
"deprecated",
"deprecated_attribute",
"deprecated_renamed_argument",
"format_doc",
"lazyproperty",
"sharedmethod",
]
_NotFound = object()
[docs]def deprecated(
since,
message="",
name="",
alternative="",
pending=False,
obj_type=None,
warning_type=AstropyDeprecationWarning,
):
"""
Used to mark a function or class as deprecated.
To mark an attribute as deprecated, use `deprecated_attribute`.
Parameters
----------
since : str
The release at which this API became deprecated. This is
required.
message : str, optional
Override the default deprecation message. The format
specifier ``func`` may be used for the name of the function,
and ``alternative`` may be used in the deprecation message
to insert the name of an alternative to the deprecated
function. ``obj_type`` may be used to insert a friendly name
for the type of object being deprecated.
name : str, optional
The name of the deprecated function or class; if not provided
the name is automatically determined from the passed in
function or class, though this is useful in the case of
renamed functions, where the new function is just assigned to
the name of the deprecated function. For example::
def new_function():
...
oldFunction = new_function
alternative : str, optional
An alternative function or class name that the user may use in
place of the deprecated object. The deprecation warning will
tell the user about this alternative if provided.
pending : bool, optional
If True, uses a AstropyPendingDeprecationWarning instead of a
``warning_type``.
obj_type : str, optional
The type of this object, if the automatically determined one
needs to be overridden.
warning_type : Warning
Warning to be issued.
Default is `~astropy.utils.exceptions.AstropyDeprecationWarning`.
"""
method_types = (classmethod, staticmethod, types.MethodType)
def deprecate_doc(old_doc, message):
"""
Returns a given docstring with a deprecation message prepended
to it.
"""
if not old_doc:
old_doc = ""
old_doc = textwrap.dedent(old_doc).strip("\n")
new_doc = f"\n.. deprecated:: {since}\n {message.strip()}\n\n" + old_doc
if not old_doc:
# This is to prevent a spurious 'unexpected unindent' warning from
# docutils when the original docstring was blank.
new_doc += r"\ "
return new_doc
def get_function(func):
"""
Given a function or classmethod (or other function wrapper type), get
the function object.
"""
if isinstance(func, method_types):
func = func.__func__
return func
def deprecate_function(func, message, warning_type=warning_type):
"""
Returns a wrapped function that displays ``warning_type``
when it is called.
"""
if isinstance(func, method_types):
func_wrapper = type(func)
else:
func_wrapper = lambda f: f # noqa: E731
func = get_function(func)
def deprecated_func(*args, **kwargs):
if pending:
category = AstropyPendingDeprecationWarning
else:
category = warning_type
warnings.warn(message, category, stacklevel=2)
return func(*args, **kwargs)
# If this is an extension function, we can't call
# functools.wraps on it, but we normally don't care.
# This crazy way to get the type of a wrapper descriptor is
# straight out of the Python 3.3 inspect module docs.
if type(func) is not type(str.__dict__["__add__"]): # noqa: E721
deprecated_func = functools.wraps(func)(deprecated_func)
deprecated_func.__doc__ = deprecate_doc(deprecated_func.__doc__, message)
return func_wrapper(deprecated_func)
def deprecate_class(cls, message, warning_type=warning_type):
"""
Update the docstring and wrap the ``__init__`` in-place (or ``__new__``
if the class or any of the bases overrides ``__new__``) so it will give
a deprecation warning when an instance is created.
This won't work for extension classes because these can't be modified
in-place and the alternatives don't work in the general case:
- Using a new class that looks and behaves like the original doesn't
work because the __new__ method of extension types usually makes sure
that it's the same class or a subclass.
- Subclassing the class and return the subclass can lead to problems
with pickle and will look weird in the Sphinx docs.
"""
cls.__doc__ = deprecate_doc(cls.__doc__, message)
if cls.__new__ is object.__new__:
cls.__init__ = deprecate_function(
get_function(cls.__init__), message, warning_type
)
else:
cls.__new__ = deprecate_function(
get_function(cls.__new__), message, warning_type
)
return cls
def deprecate(
obj,
message=message,
name=name,
alternative=alternative,
pending=pending,
warning_type=warning_type,
):
if obj_type is None:
if isinstance(obj, type):
obj_type_name = "class"
elif inspect.isfunction(obj):
obj_type_name = "function"
elif inspect.ismethod(obj) or isinstance(obj, method_types):
obj_type_name = "method"
else:
obj_type_name = "object"
else:
obj_type_name = obj_type
if not name:
name = get_function(obj).__name__
altmessage = ""
if not message or type(message) is type(deprecate):
if pending:
message = (
"The {func} {obj_type} will be deprecated in a future version."
)
else:
message = (
"The {func} {obj_type} is deprecated and may "
"be removed in a future version."
)
if alternative:
altmessage = f"\n Use {alternative} instead."
message = (
message.format(
**{
"func": name,
"name": name,
"alternative": alternative,
"obj_type": obj_type_name,
}
)
) + altmessage
if isinstance(obj, type):
return deprecate_class(obj, message, warning_type)
else:
return deprecate_function(obj, message, warning_type)
if type(message) is type(deprecate):
return deprecate(message)
return deprecate
[docs]def deprecated_attribute(
name,
since,
message=None,
alternative=None,
pending=False,
warning_type=AstropyDeprecationWarning,
):
"""
Used to mark a public attribute as deprecated. This creates a
property that will warn when the given attribute name is accessed.
To prevent the warning (i.e. for internal code), use the private
name for the attribute by prepending an underscore
(i.e. ``self._name``), or set an alternative explicitly.
Parameters
----------
name : str
The name of the deprecated attribute.
since : str
The release at which this API became deprecated. This is
required.
message : str, optional
Override the default deprecation message. The format
specifier ``name`` may be used for the name of the attribute,
and ``alternative`` may be used in the deprecation message
to insert the name of an alternative to the deprecated
function.
alternative : str, optional
An alternative attribute that the user may use in place of the
deprecated attribute. The deprecation warning will tell the
user about this alternative if provided.
pending : bool, optional
If True, uses a AstropyPendingDeprecationWarning instead of
``warning_type``.
warning_type : Warning
Warning to be issued.
Default is `~astropy.utils.exceptions.AstropyDeprecationWarning`.
Examples
--------
::
class MyClass:
# Mark the old_name as deprecated
old_name = deprecated_attribute("old_name", "0.1")
def method(self):
self._old_name = 42
class MyClass2:
old_name = deprecated_attribute(
"old_name", "1.2", alternative="new_name"
)
def method(self):
self.new_name = 24
"""
private_name = alternative or "_" + name
specific_deprecated = deprecated(
since,
name=name,
obj_type="attribute",
message=message,
alternative=alternative,
pending=pending,
warning_type=warning_type,
)
@specific_deprecated
def get(self):
return getattr(self, private_name)
@specific_deprecated
def set(self, val):
setattr(self, private_name, val)
@specific_deprecated
def delete(self):
delattr(self, private_name)
return property(get, set, delete)
[docs]def deprecated_renamed_argument(
old_name,
new_name,
since,
arg_in_kwargs=False,
relax=False,
pending=False,
warning_type=AstropyDeprecationWarning,
alternative="",
message="",
):
"""Deprecate a _renamed_ or _removed_ function argument.
The decorator assumes that the argument with the ``old_name`` was removed
from the function signature and the ``new_name`` replaced it at the
**same position** in the signature. If the ``old_name`` argument is
given when calling the decorated function the decorator will catch it and
issue a deprecation warning and pass it on as ``new_name`` argument.
Parameters
----------
old_name : str or sequence of str
The old name of the argument.
new_name : str or sequence of str or None
The new name of the argument. Set this to `None` to remove the
argument ``old_name`` instead of renaming it.
since : str or number or sequence of str or number
The release at which the old argument became deprecated.
arg_in_kwargs : bool or sequence of bool, optional
If the argument is not a named argument (for example it
was meant to be consumed by ``**kwargs``) set this to
``True``. Otherwise the decorator will throw an Exception
if the ``new_name`` cannot be found in the signature of
the decorated function.
Default is ``False``.
relax : bool or sequence of bool, optional
If ``False`` a ``TypeError`` is raised if both ``new_name`` and
``old_name`` are given. If ``True`` the value for ``new_name`` is used
and a Warning is issued.
Default is ``False``.
pending : bool or sequence of bool, optional
If ``True`` this will hide the deprecation warning and ignore the
corresponding ``relax`` parameter value.
Default is ``False``.
warning_type : Warning
Warning to be issued.
Default is `~astropy.utils.exceptions.AstropyDeprecationWarning`.
alternative : str, optional
An alternative function or class name that the user may use in
place of the deprecated object if ``new_name`` is None. The deprecation
warning will tell the user about this alternative if provided.
message : str, optional
A custom warning message. If provided then ``since`` and
``alternative`` options will have no effect.
Raises
------
TypeError
If the new argument name cannot be found in the function
signature and arg_in_kwargs was False or if it is used to
deprecate the name of the ``*args``-, ``**kwargs``-like arguments.
At runtime such an Error is raised if both the new_name
and old_name were specified when calling the function and
"relax=False".
Notes
-----
The decorator should be applied to a function where the **name**
of an argument was changed but it applies the same logic.
.. warning::
If ``old_name`` is a list or tuple the ``new_name`` and ``since`` must
also be a list or tuple with the same number of entries. ``relax`` and
``arg_in_kwarg`` can be a single bool (applied to all) or also a
list/tuple with the same number of entries like ``new_name``, etc.
Examples
--------
The deprecation warnings are not shown in the following examples.
To deprecate a positional or keyword argument::
>>> from astropy.utils.decorators import deprecated_renamed_argument
>>> @deprecated_renamed_argument('sig', 'sigma', '1.0')
... def test(sigma):
... return sigma
>>> test(2)
2
>>> test(sigma=2)
2
>>> test(sig=2) # doctest: +SKIP
2
To deprecate an argument caught inside the ``**kwargs`` the
``arg_in_kwargs`` has to be set::
>>> @deprecated_renamed_argument('sig', 'sigma', '1.0',
... arg_in_kwargs=True)
... def test(**kwargs):
... return kwargs['sigma']
>>> test(sigma=2)
2
>>> test(sig=2) # doctest: +SKIP
2
By default providing the new and old keyword will lead to an Exception. If
a Warning is desired set the ``relax`` argument::
>>> @deprecated_renamed_argument('sig', 'sigma', '1.0', relax=True)
... def test(sigma):
... return sigma
>>> test(sig=2) # doctest: +SKIP
2
It is also possible to replace multiple arguments. The ``old_name``,
``new_name`` and ``since`` have to be `tuple` or `list` and contain the
same number of entries::
>>> @deprecated_renamed_argument(['a', 'b'], ['alpha', 'beta'],
... ['1.0', 1.2])
... def test(alpha, beta):
... return alpha, beta
>>> test(a=2, b=3) # doctest: +SKIP
(2, 3)
In this case ``arg_in_kwargs`` and ``relax`` can be a single value (which
is applied to all renamed arguments) or must also be a `tuple` or `list`
with values for each of the arguments.
"""
cls_iter = (list, tuple)
if isinstance(old_name, cls_iter):
n = len(old_name)
# Assume that new_name and since are correct (tuple/list with the
# appropriate length) in the spirit of the "consenting adults". But the
# optional parameters may not be set, so if these are not iterables
# wrap them.
if not isinstance(arg_in_kwargs, cls_iter):
arg_in_kwargs = [arg_in_kwargs] * n
if not isinstance(relax, cls_iter):
relax = [relax] * n
if not isinstance(pending, cls_iter):
pending = [pending] * n
if not isinstance(message, cls_iter):
message = [message] * n
else:
# To allow a uniform approach later on, wrap all arguments in lists.
n = 1
old_name = [old_name]
new_name = [new_name]
since = [since]
arg_in_kwargs = [arg_in_kwargs]
relax = [relax]
pending = [pending]
message = [message]
def decorator(function):
# The named arguments of the function.
arguments = signature(function).parameters
keys = list(arguments.keys())
position = [None] * n
for i in range(n):
# Determine the position of the argument.
if arg_in_kwargs[i]:
pass
else:
if new_name[i] is None:
param = arguments[old_name[i]]
elif new_name[i] in arguments:
param = arguments[new_name[i]]
# In case the argument is not found in the list of arguments
# the only remaining possibility is that it should be caught
# by some kind of **kwargs argument.
# This case has to be explicitly specified, otherwise throw
# an exception!
else:
raise TypeError(
f'"{new_name[i]}" was not specified in the function '
"signature. If it was meant to be part of "
'"**kwargs" then set "arg_in_kwargs" to "True"'
)
# There are several possibilities now:
# 1.) Positional or keyword argument:
if param.kind == param.POSITIONAL_OR_KEYWORD:
if new_name[i] is None:
position[i] = keys.index(old_name[i])
else:
position[i] = keys.index(new_name[i])
# 2.) Keyword only argument:
elif param.kind == param.KEYWORD_ONLY:
# These cannot be specified by position.
position[i] = None
# 3.) positional-only argument, varargs, varkwargs or some
# unknown type:
else:
raise TypeError(
f'cannot replace argument "{new_name[i]}" '
f"of kind {repr(param.kind)}."
)
@functools.wraps(function)
def wrapper(*args, **kwargs):
for i in range(n):
msg = message[i] or (
f'"{old_name[i]}" was deprecated in '
f"version {since[i]} and will be removed "
"in a future version. "
)
# The only way to have oldkeyword inside the function is
# that it is passed as kwarg because the oldkeyword
# parameter was renamed to newkeyword.
if old_name[i] in kwargs:
value = kwargs.pop(old_name[i])
# Display the deprecation warning only when it's not
# pending.
if not pending[i]:
if not message[i]:
if new_name[i] is not None:
msg += f'Use argument "{new_name[i]}" instead.'
elif alternative:
msg += f"\n Use {alternative} instead."
warnings.warn(msg, warning_type, stacklevel=2)
# Check if the newkeyword was given as well.
newarg_in_args = position[i] is not None and len(args) > position[i]
newarg_in_kwargs = new_name[i] in kwargs
if newarg_in_args or newarg_in_kwargs:
if not pending[i]:
# If both are given print a Warning if relax is
# True or raise an Exception is relax is False.
if relax[i]:
warnings.warn(
f'"{old_name[i]}" and "{new_name[i]}" '
"keywords were set. "
f'Using the value of "{new_name[i]}".',
AstropyUserWarning,
)
else:
raise TypeError(
f'cannot specify both "{old_name[i]}" and '
f'"{new_name[i]}".'
)
else:
# Pass the value of the old argument with the
# name of the new argument to the function
if new_name[i] is not None:
kwargs[new_name[i]] = value
# If old argument has no replacement, cast it back.
# https://github.com/astropy/astropy/issues/9914
else:
kwargs[old_name[i]] = value
# Deprecated keyword without replacement is given as
# positional argument.
elif (
not pending[i]
and not new_name[i]
and position[i]
and len(args) > position[i]
):
if alternative and not message[i]:
msg += f"\n Use {alternative} instead."
warnings.warn(msg, warning_type, stacklevel=2)
return function(*args, **kwargs)
return wrapper
return decorator
# TODO: This can still be made to work for setters by implementing an
# accompanying metaclass that supports it; we just don't need that right this
# second
[docs]class classproperty(property):
"""
Similar to `property`, but allows class-level properties. That is,
a property whose getter is like a `classmethod`.
The wrapped method may explicitly use the `classmethod` decorator (which
must become before this decorator), or the `classmethod` may be omitted
(it is implicit through use of this decorator).
.. note::
classproperty only works for *read-only* properties. It does not
currently allow writeable/deletable properties, due to subtleties of how
Python descriptors work. In order to implement such properties on a class
a metaclass for that class must be implemented.
Parameters
----------
fget : callable
The function that computes the value of this property (in particular,
the function when this is used as a decorator) a la `property`.
doc : str, optional
The docstring for the property--by default inherited from the getter
function.
lazy : bool, optional
If True, caches the value returned by the first call to the getter
function, so that it is only called once (used for lazy evaluation
of an attribute). This is analogous to `lazyproperty`. The ``lazy``
argument can also be used when `classproperty` is used as a decorator
(see the third example below). When used in the decorator syntax this
*must* be passed in as a keyword argument.
Examples
--------
::
>>> class Foo:
... _bar_internal = 1
... @classproperty
... def bar(cls):
... return cls._bar_internal + 1
...
>>> Foo.bar
2
>>> foo_instance = Foo()
>>> foo_instance.bar
2
>>> foo_instance._bar_internal = 2
>>> foo_instance.bar # Ignores instance attributes
2
As previously noted, a `classproperty` is limited to implementing
read-only attributes::
>>> class Foo:
... _bar_internal = 1
... @classproperty
... def bar(cls):
... return cls._bar_internal
... @bar.setter
... def bar(cls, value):
... cls._bar_internal = value
...
Traceback (most recent call last):
...
NotImplementedError: classproperty can only be read-only; use a
metaclass to implement modifiable class-level properties
When the ``lazy`` option is used, the getter is only called once::
>>> class Foo:
... @classproperty(lazy=True)
... def bar(cls):
... print("Performing complicated calculation")
... return 1
...
>>> Foo.bar
Performing complicated calculation
1
>>> Foo.bar
1
If a subclass inherits a lazy `classproperty` the property is still
re-evaluated for the subclass::
>>> class FooSub(Foo):
... pass
...
>>> FooSub.bar
Performing complicated calculation
1
>>> FooSub.bar
1
"""
def __new__(cls, fget=None, doc=None, lazy=False):
if fget is None:
# Being used as a decorator--return a wrapper that implements
# decorator syntax
def wrapper(func):
return cls(func, lazy=lazy)
return wrapper
return super().__new__(cls)
def __init__(self, fget, doc=None, lazy=False):
self._lazy = lazy
if lazy:
self._lock = threading.RLock() # Protects _cache
self._cache = {}
fget = self._wrap_fget(fget)
super().__init__(fget=fget, doc=doc)
# There is a buglet in Python where self.__doc__ doesn't
# get set properly on instances of property subclasses if
# the doc argument was used rather than taking the docstring
# from fget
# Related Python issue: https://bugs.python.org/issue24766
if doc is not None:
self.__doc__ = doc
def __get__(self, obj, objtype):
if self._lazy:
val = self._cache.get(objtype, _NotFound)
if val is _NotFound:
with self._lock:
# Check if another thread initialised before we locked.
val = self._cache.get(objtype, _NotFound)
if val is _NotFound:
val = self.fget.__wrapped__(objtype)
self._cache[objtype] = val
else:
# The base property.__get__ will just return self here;
# instead we pass objtype through to the original wrapped
# function (which takes the class as its sole argument)
val = self.fget.__wrapped__(objtype)
return val
[docs] def getter(self, fget):
return super().getter(self._wrap_fget(fget))
[docs] def setter(self, fset):
raise NotImplementedError(
"classproperty can only be read-only; use a metaclass to "
"implement modifiable class-level properties"
)
[docs] def deleter(self, fdel):
raise NotImplementedError(
"classproperty can only be read-only; use a metaclass to "
"implement modifiable class-level properties"
)
@staticmethod
def _wrap_fget(orig_fget):
if isinstance(orig_fget, classmethod):
orig_fget = orig_fget.__func__
# Using stock functools.wraps instead of the fancier version
# found later in this module, which is overkill for this purpose
@functools.wraps(orig_fget)
def fget(obj):
return orig_fget(obj.__class__)
return fget
# Adapted from the recipe at
# http://code.activestate.com/recipes/363602-lazy-property-evaluation
[docs]class lazyproperty(property):
"""
Works similarly to property(), but computes the value only once.
This essentially memorizes the value of the property by storing the result
of its computation in the ``__dict__`` of the object instance. This is
useful for computing the value of some property that should otherwise be
invariant. For example::
>>> class LazyTest:
... @lazyproperty
... def complicated_property(self):
... print('Computing the value for complicated_property...')
... return 42
...
>>> lt = LazyTest()
>>> lt.complicated_property
Computing the value for complicated_property...
42
>>> lt.complicated_property
42
As the example shows, the second time ``complicated_property`` is accessed,
the ``print`` statement is not executed. Only the return value from the
first access off ``complicated_property`` is returned.
By default, a setter and deleter are used which simply overwrite and
delete, respectively, the value stored in ``__dict__``. Any user-specified
setter or deleter is executed before executing these default actions.
The one exception is that the default setter is not run if the user setter
already sets the new value in ``__dict__`` and returns that value and the
returned value is not ``None``.
"""
def __init__(self, fget, fset=None, fdel=None, doc=None):
super().__init__(fget, fset, fdel, doc)
self._key = self.fget.__name__
self._lock = threading.RLock()
def __get__(self, obj, owner=None):
try:
obj_dict = obj.__dict__
val = obj_dict.get(self._key, _NotFound)
if val is _NotFound:
with self._lock:
# Check if another thread beat us to it.
val = obj_dict.get(self._key, _NotFound)
if val is _NotFound:
val = self.fget(obj)
obj_dict[self._key] = val
return val
except AttributeError:
if obj is None:
return self
raise
def __set__(self, obj, val):
obj_dict = obj.__dict__
if self.fset:
ret = self.fset(obj, val)
if ret is not None and obj_dict.get(self._key) is ret:
# By returning the value set the setter signals that it
# took over setting the value in obj.__dict__; this
# mechanism allows it to override the input value
return
obj_dict[self._key] = val
def __delete__(self, obj):
if self.fdel:
self.fdel(obj)
obj.__dict__.pop(self._key, None) # Delete if present
[docs]class sharedmethod(classmethod):
"""
This is a method decorator that allows both an instancemethod and a
`classmethod` to share the same name.
When using `sharedmethod` on a method defined in a class's body, it
may be called on an instance, or on a class. In the former case it
behaves like a normal instance method (a reference to the instance is
automatically passed as the first ``self`` argument of the method)::
>>> class Example:
... @sharedmethod
... def identify(self, *args):
... print('self was', self)
... print('additional args were', args)
...
>>> ex = Example()
>>> ex.identify(1, 2)
self was <astropy.utils.decorators.Example object at 0x...>
additional args were (1, 2)
In the latter case, when the `sharedmethod` is called directly from a
class, it behaves like a `classmethod`::
>>> Example.identify(3, 4)
self was <class 'astropy.utils.decorators.Example'>
additional args were (3, 4)
This also supports a more advanced usage, where the `classmethod`
implementation can be written separately. If the class's *metaclass*
has a method of the same name as the `sharedmethod`, the version on
the metaclass is delegated to::
>>> class ExampleMeta(type):
... def identify(self):
... print('this implements the {0}.identify '
... 'classmethod'.format(self.__name__))
...
>>> class Example(metaclass=ExampleMeta):
... @sharedmethod
... def identify(self):
... print('this implements the instancemethod')
...
>>> Example().identify()
this implements the instancemethod
>>> Example.identify()
this implements the Example.identify classmethod
"""
def __get__(self, obj, objtype=None):
if obj is None:
mcls = type(objtype)
clsmeth = getattr(mcls, self.__func__.__name__, None)
if callable(clsmeth):
func = clsmeth
else:
func = self.__func__
return self._make_method(func, objtype)
else:
return self._make_method(self.__func__, obj)
@staticmethod
def _make_method(func, instance):
return types.MethodType(func, instance)