# -*- coding: utf-8 -*-
# Licensed under a 3-clause BSD style license - see LICENSE.rst
"""Sundry function and class decorators."""
import functools
import inspect
import textwrap
import types
import warnings
from inspect import signature
from .codegen import make_function_with_signature
from .exceptions import (AstropyDeprecationWarning, AstropyUserWarning,
AstropyPendingDeprecationWarning)
__all__ = ['classproperty', 'deprecated', 'deprecated_attribute',
'deprecated_renamed_argument', 'format_doc',
'lazyproperty', 'sharedmethod', 'wraps']
def deprecated(since, message='', name='', alternative='', pending=False,
obj_type=None):
"""
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
AstropyDeprecationWarning.
obj_type : str, optional
The type of this object, if the automatically determined one
needs to be overridden.
"""
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 = (('\n.. deprecated:: {since}'
'\n {message}\n\n'.format(
**{'since': since, 'message': message.strip()})) + 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):
"""
Returns a wrapped function that displays an
``AstropyDeprecationWarning`` when it is called.
"""
if isinstance(func, method_types):
func_wrapper = type(func)
else:
func_wrapper = lambda f: f
func = get_function(func)
def deprecated_func(*args, **kwargs):
if pending:
category = AstropyPendingDeprecationWarning
else:
category = AstropyDeprecationWarning
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__']): # nopep8
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):
"""
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)
else:
cls.__new__ = deprecate_function(get_function(cls.__new__), message)
return cls
def deprecate(obj, message=message, name=name, alternative=alternative,
pending=pending):
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 = '\n Use {} instead.'.format(alternative)
message = ((message.format(**{
'func': name,
'name': name,
'alternative': alternative,
'obj_type': obj_type_name})) +
altmessage)
if isinstance(obj, type):
return deprecate_class(obj, message)
else:
return deprecate_function(obj, message)
if type(message) is type(deprecate):
return deprecate(message)
return deprecate
def deprecated_attribute(name, since, message=None, alternative=None,
pending=False):
"""
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``).
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 a
AstropyDeprecationWarning.
Examples
--------
::
class MyClass:
# Mark the old_name as deprecated
old_name = misc.deprecated_attribute('old_name', '0.1')
def method(self):
self._old_name = 42
"""
private_name = '_' + name
@deprecated(since, name=name, obj_type='attribute')
def get(self):
return getattr(self, private_name)
@deprecated(since, name=name, obj_type='attribute')
def set(self, val):
setattr(self, private_name, val)
@deprecated(since, name=name, obj_type='attribute')
def delete(self):
delattr(self, private_name)
return property(get, set, delete)
def deprecated_renamed_argument(old_name, new_name, since,
arg_in_kwargs=False, relax=False,
pending=False):
"""Deprecate a _renamed_ 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 list/tuple thereof
The old name of the argument.
new_name : str or list/tuple thereof
The new name of the argument.
since : str or number or list/tuple thereof
The release at which the old argument became deprecated.
arg_in_kwargs : bool or list/tuple thereof, 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 list/tuple thereof, 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 list/tuple thereof, optional
If ``True`` this will hide the deprecation warning and ignore the
corresponding ``relax`` parameter value.
Default is ``False``.
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)
2
To deprecate an argument catched 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)
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)
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)
(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
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]
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 new_name[i] in arguments:
param = arguments[new_name[i]]
# There are several possibilities now:
# 1.) Positional or keyword argument:
if param.kind == param.POSITIONAL_OR_KEYWORD:
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('cannot replace argument "{0}" of kind '
'{1!r}.'.format(new_name[i], param.kind))
# In case the argument is not found in the list of arguments
# the only remaining possibility is that it should be catched
# by some kind of **kwargs argument.
# This case has to be explicitly specified, otherwise throw
# an exception!
elif arg_in_kwargs[i]:
position[i] = None
else:
raise TypeError('"{}" was not specified in the function '
'signature. If it was meant to be part of '
'"**kwargs" then set "arg_in_kwargs" to "True"'
'.'.format(new_name[i]))
@functools.wraps(function)
def wrapper(*args, **kwargs):
for i in range(n):
# 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 only
# pending.
if not pending[i]:
warnings.warn(
'"{0}" was deprecated in version {1} '
'and will be removed in a future version. '
'Use argument "{2}" instead.'
''.format(old_name[i], since[i], new_name[i]),
AstropyDeprecationWarning, 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(
'"{0}" and "{1}" keywords were set. '
'Using the value of "{1}".'
''.format(old_name[i], new_name[i]),
AstropyUserWarning)
else:
raise TypeError(
'cannot specify both "{}" and "{}"'
'.'.format(old_name[i], new_name[i]))
else:
# If the new argument isn't specified just pass the old
# one with the name of the new argument to the function
kwargs[new_name[i]] = value
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
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/deleteable 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._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 and objtype in self._cache:
return self._cache[objtype]
# 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)
if self._lazy:
self._cache[objtype] = val
return val
def getter(self, fget):
return super().getter(self._wrap_fget(fget))
def setter(self, fset):
raise NotImplementedError(
"classproperty can only be read-only; use a metaclass to "
"implement modifiable class-level properties")
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
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``.
Adapted from the recipe at
http://code.activestate.com/recipes/363602-lazy-property-evaluation
"""
def __init__(self, fget, fset=None, fdel=None, doc=None):
super().__init__(fget, fset, fdel, doc)
self._key = self.fget.__name__
def __get__(self, obj, owner=None):
try:
return obj.__dict__[self._key]
except KeyError:
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)
if self._key in obj.__dict__:
del obj.__dict__[self._key]
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)
def wraps(wrapped, assigned=functools.WRAPPER_ASSIGNMENTS,
updated=functools.WRAPPER_UPDATES, exclude_args=()):
"""
An alternative to `functools.wraps` which also preserves the original
function's call signature by way of
`~astropy.utils.codegen.make_function_with_signature`.
This also adds an optional ``exclude_args`` argument. If given it should
be a sequence of argument names that should not be copied from the wrapped
function (either positional or keyword arguments).
The documentation for the original `functools.wraps` follows:
"""
wrapped_args = _get_function_args(wrapped, exclude_args=exclude_args)
def wrapper(func):
if '__name__' in assigned:
name = wrapped.__name__
else:
name = func.__name__
func = make_function_with_signature(func, name=name, **wrapped_args)
func = functools.update_wrapper(func, wrapped, assigned=assigned,
updated=updated)
return func
return wrapper
if (isinstance(wraps.__doc__, str) and
wraps.__doc__ is not None and functools.wraps.__doc__ is not None):
wraps.__doc__ += functools.wraps.__doc__
def _get_function_args_internal(func):
"""
Utility function for `wraps`.
Reads the argspec for the given function and converts it to arguments
for `make_function_with_signature`.
"""
argspec = inspect.getfullargspec(func)
if argspec.defaults:
args = argspec.args[:-len(argspec.defaults)]
kwargs = zip(argspec.args[len(args):], argspec.defaults)
else:
args = argspec.args
kwargs = []
if argspec.kwonlyargs:
kwargs.extend((argname, argspec.kwonlydefaults[argname])
for argname in argspec.kwonlyargs)
return {'args': args, 'kwargs': kwargs, 'varargs': argspec.varargs,
'varkwargs': argspec.varkw}
def _get_function_args(func, exclude_args=()):
all_args = _get_function_args_internal(func)
if exclude_args:
exclude_args = set(exclude_args)
for arg_type in ('args', 'kwargs'):
all_args[arg_type] = [arg for arg in all_args[arg_type]
if arg not in exclude_args]
for arg_type in ('varargs', 'varkwargs'):
if all_args[arg_type] in exclude_args:
all_args[arg_type] = None
return all_args
def format_doc(docstring, *args, **kwargs):
"""
Replaces the docstring of the decorated object and then formats it.
The formatting works like :meth:`str.format` and if the decorated object
already has a docstring this docstring can be included in the new
documentation if you use the ``{__doc__}`` placeholder.
Its primary use is for reusing a *long* docstring in multiple functions
when it is the same or only slightly different between them.
Parameters
----------
docstring : str or object or None
The docstring that will replace the docstring of the decorated
object. If it is an object like a function or class it will
take the docstring of this object. If it is a string it will use the
string itself. One special case is if the string is ``None`` then
it will use the decorated functions docstring and formats it.
args :
passed to :meth:`str.format`.
kwargs :
passed to :meth:`str.format`. If the function has a (not empty)
docstring the original docstring is added to the kwargs with the
keyword ``'__doc__'``.
Raises
------
ValueError
If the ``docstring`` (or interpreted docstring if it was ``None``
or not a string) is empty.
IndexError, KeyError
If a placeholder in the (interpreted) ``docstring`` was not filled. see
:meth:`str.format` for more information.
Notes
-----
Using this decorator allows, for example Sphinx, to parse the
correct docstring.
Examples
--------
Replacing the current docstring is very easy::
>>> from astropy.utils.decorators import format_doc
>>> @format_doc('''Perform num1 + num2''')
... def add(num1, num2):
... return num1+num2
...
>>> help(add) # doctest: +SKIP
Help on function add in module __main__:
<BLANKLINE>
add(num1, num2)
Perform num1 + num2
sometimes instead of replacing you only want to add to it::
>>> doc = '''
... {__doc__}
... Parameters
... ----------
... num1, num2 : Numbers
... Returns
... -------
... result: Number
... '''
>>> @format_doc(doc)
... def add(num1, num2):
... '''Perform addition.'''
... return num1+num2
...
>>> help(add) # doctest: +SKIP
Help on function add in module __main__:
<BLANKLINE>
add(num1, num2)
Perform addition.
Parameters
----------
num1, num2 : Numbers
Returns
-------
result : Number
in case one might want to format it further::
>>> doc = '''
... Perform {0}.
... Parameters
... ----------
... num1, num2 : Numbers
... Returns
... -------
... result: Number
... result of num1 {op} num2
... {__doc__}
... '''
>>> @format_doc(doc, 'addition', op='+')
... def add(num1, num2):
... return num1+num2
...
>>> @format_doc(doc, 'subtraction', op='-')
... def subtract(num1, num2):
... '''Notes: This one has additional notes.'''
... return num1-num2
...
>>> help(add) # doctest: +SKIP
Help on function add in module __main__:
<BLANKLINE>
add(num1, num2)
Perform addition.
Parameters
----------
num1, num2 : Numbers
Returns
-------
result : Number
result of num1 + num2
>>> help(subtract) # doctest: +SKIP
Help on function subtract in module __main__:
<BLANKLINE>
subtract(num1, num2)
Perform subtraction.
Parameters
----------
num1, num2 : Numbers
Returns
-------
result : Number
result of num1 - num2
Notes : This one has additional notes.
These methods can be combined an even taking the docstring from another
object is possible as docstring attribute. You just have to specify the
object::
>>> @format_doc(add)
... def another_add(num1, num2):
... return num1 + num2
...
>>> help(another_add) # doctest: +SKIP
Help on function another_add in module __main__:
<BLANKLINE>
another_add(num1, num2)
Perform addition.
Parameters
----------
num1, num2 : Numbers
Returns
-------
result : Number
result of num1 + num2
But be aware that this decorator *only* formats the given docstring not
the strings passed as ``args`` or ``kwargs`` (not even the original
docstring)::
>>> @format_doc(doc, 'addition', op='+')
... def yet_another_add(num1, num2):
... '''This one is good for {0}.'''
... return num1 + num2
...
>>> help(yet_another_add) # doctest: +SKIP
Help on function yet_another_add in module __main__:
<BLANKLINE>
yet_another_add(num1, num2)
Perform addition.
Parameters
----------
num1, num2 : Numbers
Returns
-------
result : Number
result of num1 + num2
This one is good for {0}.
To work around it you could specify the docstring to be ``None``::
>>> @format_doc(None, 'addition')
... def last_add_i_swear(num1, num2):
... '''This one is good for {0}.'''
... return num1 + num2
...
>>> help(last_add_i_swear) # doctest: +SKIP
Help on function last_add_i_swear in module __main__:
<BLANKLINE>
last_add_i_swear(num1, num2)
This one is good for addition.
Using it with ``None`` as docstring allows to use the decorator twice
on an object to first parse the new docstring and then to parse the
original docstring or the ``args`` and ``kwargs``.
"""
def set_docstring(obj):
if docstring is None:
# None means: use the objects __doc__
doc = obj.__doc__
# Delete documentation in this case so we don't end up with
# awkwardly self-inserted docs.
obj.__doc__ = None
elif isinstance(docstring, str):
# String: use the string that was given
doc = docstring
else:
# Something else: Use the __doc__ of this
doc = docstring.__doc__
if not doc:
# In case the docstring is empty it's probably not what was wanted.
raise ValueError('docstring must be a string or containing a '
'docstring that is not empty.')
# If the original has a not-empty docstring append it to the format
# kwargs.
kwargs['__doc__'] = obj.__doc__ or ''
obj.__doc__ = doc.format(*args, **kwargs)
return obj
return set_docstring