from functools import reduce, partial
import inspect
import operator
from operator import attrgetter
from importlib import import_module
from textwrap import dedent
from types import MethodType
from .compatibility import PY3, PY34, PYPY
from .utils import no_default
__all__ = ('identity', 'apply', 'thread_first', 'thread_last', 'memoize',
'compose', 'compose_left', 'pipe', 'complement', 'juxt', 'do',
'curry', 'flip', 'excepts')
[docs]def identity(x):
""" Identity function. Return x
>>> identity(3)
3
"""
return x
[docs]def apply(*func_and_args, **kwargs):
""" Applies a function and returns the results
>>> def double(x): return 2*x
>>> def inc(x): return x + 1
>>> apply(double, 5)
10
>>> tuple(map(apply, [double, inc, double], [10, 500, 8000]))
(20, 501, 16000)
"""
if not func_and_args:
raise TypeError('func argument is required')
func, args = func_and_args[0], func_and_args[1:]
return func(*args, **kwargs)
[docs]def thread_first(val, *forms):
""" Thread value through a sequence of functions/forms
>>> def double(x): return 2*x
>>> def inc(x): return x + 1
>>> thread_first(1, inc, double)
4
If the function expects more than one input you can specify those inputs
in a tuple. The value is used as the first input.
>>> def add(x, y): return x + y
>>> def pow(x, y): return x**y
>>> thread_first(1, (add, 4), (pow, 2)) # pow(add(1, 4), 2)
25
So in general
thread_first(x, f, (g, y, z))
expands to
g(f(x), y, z)
See Also:
thread_last
"""
def evalform_front(val, form):
if callable(form):
return form(val)
if isinstance(form, tuple):
func, args = form[0], form[1:]
args = (val,) + args
return func(*args)
return reduce(evalform_front, forms, val)
[docs]def thread_last(val, *forms):
""" Thread value through a sequence of functions/forms
>>> def double(x): return 2*x
>>> def inc(x): return x + 1
>>> thread_last(1, inc, double)
4
If the function expects more than one input you can specify those inputs
in a tuple. The value is used as the last input.
>>> def add(x, y): return x + y
>>> def pow(x, y): return x**y
>>> thread_last(1, (add, 4), (pow, 2)) # pow(2, add(4, 1))
32
So in general
thread_last(x, f, (g, y, z))
expands to
g(y, z, f(x))
>>> def iseven(x):
... return x % 2 == 0
>>> list(thread_last([1, 2, 3], (map, inc), (filter, iseven)))
[2, 4]
See Also:
thread_first
"""
def evalform_back(val, form):
if callable(form):
return form(val)
if isinstance(form, tuple):
func, args = form[0], form[1:]
args = args + (val,)
return func(*args)
return reduce(evalform_back, forms, val)
def instanceproperty(fget=None, fset=None, fdel=None, doc=None, classval=None):
""" Like @property, but returns ``classval`` when used as a class attribute
>>> class MyClass(object):
... '''The class docstring'''
... @instanceproperty(classval=__doc__)
... def __doc__(self):
... return 'An object docstring'
... @instanceproperty
... def val(self):
... return 42
...
>>> MyClass.__doc__
'The class docstring'
>>> MyClass.val is None
True
>>> obj = MyClass()
>>> obj.__doc__
'An object docstring'
>>> obj.val
42
"""
if fget is None:
return partial(instanceproperty, fset=fset, fdel=fdel, doc=doc,
classval=classval)
return InstanceProperty(fget=fget, fset=fset, fdel=fdel, doc=doc,
classval=classval)
class InstanceProperty(property):
""" Like @property, but returns ``classval`` when used as a class attribute
Should not be used directly. Use ``instanceproperty`` instead.
"""
def __init__(self, fget=None, fset=None, fdel=None, doc=None,
classval=None):
self.classval = classval
property.__init__(self, fget=fget, fset=fset, fdel=fdel, doc=doc)
def __get__(self, obj, type=None):
if obj is None:
return self.classval
return property.__get__(self, obj, type)
def __reduce__(self):
state = (self.fget, self.fset, self.fdel, self.__doc__, self.classval)
return InstanceProperty, state
[docs]class curry(object):
""" Curry a callable function
Enables partial application of arguments through calling a function with an
incomplete set of arguments.
>>> def mul(x, y):
... return x * y
>>> mul = curry(mul)
>>> double = mul(2)
>>> double(10)
20
Also supports keyword arguments
>>> @curry # Can use curry as a decorator
... def f(x, y, a=10):
... return a * (x + y)
>>> add = f(a=1)
>>> add(2, 3)
5
See Also:
toolz.curried - namespace of curried functions
https://toolz.readthedocs.io/en/latest/curry.html
"""
def __init__(self, *args, **kwargs):
if not args:
raise TypeError('__init__() takes at least 2 arguments (1 given)')
func, args = args[0], args[1:]
if not callable(func):
raise TypeError("Input must be callable")
# curry- or functools.partial-like object? Unpack and merge arguments
if (
hasattr(func, 'func')
and hasattr(func, 'args')
and hasattr(func, 'keywords')
and isinstance(func.args, tuple)
):
_kwargs = {}
if func.keywords:
_kwargs.update(func.keywords)
_kwargs.update(kwargs)
kwargs = _kwargs
args = func.args + args
func = func.func
if kwargs:
self._partial = partial(func, *args, **kwargs)
else:
self._partial = partial(func, *args)
self.__doc__ = getattr(func, '__doc__', None)
self.__name__ = getattr(func, '__name__', '<curry>')
self.__module__ = getattr(func, '__module__', None)
self.__qualname__ = getattr(func, '__qualname__', None)
self._sigspec = None
self._has_unknown_args = None
@instanceproperty
def func(self):
return self._partial.func
if PY3: # pragma: py2 no cover
@instanceproperty
def __signature__(self):
sig = inspect.signature(self.func)
args = self.args or ()
keywords = self.keywords or {}
if is_partial_args(self.func, args, keywords, sig) is False:
raise TypeError('curry object has incorrect arguments')
params = list(sig.parameters.values())
skip = 0
for param in params[:len(args)]:
if param.kind == param.VAR_POSITIONAL:
break
skip += 1
kwonly = False
newparams = []
for param in params[skip:]:
kind = param.kind
default = param.default
if kind == param.VAR_KEYWORD:
pass
elif kind == param.VAR_POSITIONAL:
if kwonly:
continue
elif param.name in keywords:
default = keywords[param.name]
kind = param.KEYWORD_ONLY
kwonly = True
else:
if kwonly:
kind = param.KEYWORD_ONLY
if default is param.empty:
default = no_default
newparams.append(param.replace(default=default, kind=kind))
return sig.replace(parameters=newparams)
@instanceproperty
def args(self):
return self._partial.args
@instanceproperty
def keywords(self):
return self._partial.keywords
@instanceproperty
def func_name(self):
return self.__name__
def __str__(self):
return str(self.func)
def __repr__(self):
return repr(self.func)
def __hash__(self):
return hash((self.func, self.args,
frozenset(self.keywords.items()) if self.keywords
else None))
def __eq__(self, other):
return (isinstance(other, curry) and self.func == other.func and
self.args == other.args and self.keywords == other.keywords)
def __ne__(self, other):
return not self.__eq__(other)
def __call__(self, *args, **kwargs):
try:
return self._partial(*args, **kwargs)
except TypeError as exc:
if self._should_curry(args, kwargs, exc):
return self.bind(*args, **kwargs)
raise
def _should_curry(self, args, kwargs, exc=None):
func = self.func
args = self.args + args
if self.keywords:
kwargs = dict(self.keywords, **kwargs)
if self._sigspec is None:
sigspec = self._sigspec = _sigs.signature_or_spec(func)
self._has_unknown_args = has_varargs(func, sigspec) is not False
else:
sigspec = self._sigspec
if is_partial_args(func, args, kwargs, sigspec) is False:
# Nothing can make the call valid
return False
elif self._has_unknown_args:
# The call may be valid and raised a TypeError, but we curry
# anyway because the function may have `*args`. This is useful
# for decorators with signature `func(*args, **kwargs)`.
return True
elif not is_valid_args(func, args, kwargs, sigspec):
# Adding more arguments may make the call valid
return True
else:
# There was a genuine TypeError
return False
def bind(self, *args, **kwargs):
return type(self)(self, *args, **kwargs)
def call(self, *args, **kwargs):
return self._partial(*args, **kwargs)
def __get__(self, instance, owner):
if instance is None:
return self
return curry(self, instance)
def __reduce__(self):
func = self.func
modname = getattr(func, '__module__', None)
qualname = getattr(func, '__qualname__', None)
if qualname is None: # pragma: py3 no cover
qualname = getattr(func, '__name__', None)
is_decorated = None
if modname and qualname:
attrs = []
obj = import_module(modname)
for attr in qualname.split('.'):
if isinstance(obj, curry): # pragma: py2 no cover
attrs.append('func')
obj = obj.func
obj = getattr(obj, attr, None)
if obj is None:
break
attrs.append(attr)
if isinstance(obj, curry) and obj.func is func:
is_decorated = obj is self
qualname = '.'.join(attrs)
func = '%s:%s' % (modname, qualname)
# functools.partial objects can't be pickled
userdict = tuple((k, v) for k, v in self.__dict__.items()
if k not in ('_partial', '_sigspec'))
state = (type(self), func, self.args, self.keywords, userdict,
is_decorated)
return _restore_curry, state
def _restore_curry(cls, func, args, kwargs, userdict, is_decorated):
if isinstance(func, str):
modname, qualname = func.rsplit(':', 1)
obj = import_module(modname)
for attr in qualname.split('.'):
obj = getattr(obj, attr)
if is_decorated:
return obj
func = obj.func
obj = cls(func, *args, **(kwargs or {}))
obj.__dict__.update(userdict)
return obj
[docs]@curry
def memoize(func, cache=None, key=None):
""" Cache a function's result for speedy future evaluation
Considerations:
Trades memory for speed.
Only use on pure functions.
>>> def add(x, y): return x + y
>>> add = memoize(add)
Or use as a decorator
>>> @memoize
... def add(x, y):
... return x + y
Use the ``cache`` keyword to provide a dict-like object as an initial cache
>>> @memoize(cache={(1, 2): 3})
... def add(x, y):
... return x + y
Note that the above works as a decorator because ``memoize`` is curried.
It is also possible to provide a ``key(args, kwargs)`` function that
calculates keys used for the cache, which receives an ``args`` tuple and
``kwargs`` dict as input, and must return a hashable value. However,
the default key function should be sufficient most of the time.
>>> # Use key function that ignores extraneous keyword arguments
>>> @memoize(key=lambda args, kwargs: args)
... def add(x, y, verbose=False):
... if verbose:
... print('Calculating %s + %s' % (x, y))
... return x + y
"""
if cache is None:
cache = {}
try:
may_have_kwargs = has_keywords(func) is not False
# Is unary function (single arg, no variadic argument or keywords)?
is_unary = is_arity(1, func)
except TypeError: # pragma: no cover
may_have_kwargs = True
is_unary = False
if key is None:
if is_unary:
def key(args, kwargs):
return args[0]
elif may_have_kwargs:
def key(args, kwargs):
return (
args or None,
frozenset(kwargs.items()) if kwargs else None,
)
else:
def key(args, kwargs):
return args
def memof(*args, **kwargs):
k = key(args, kwargs)
try:
return cache[k]
except TypeError:
raise TypeError("Arguments to memoized function must be hashable")
except KeyError:
cache[k] = result = func(*args, **kwargs)
return result
try:
memof.__name__ = func.__name__
except AttributeError:
pass
memof.__doc__ = func.__doc__
memof.__wrapped__ = func
return memof
class Compose(object):
""" A composition of functions
See Also:
compose
"""
__slots__ = 'first', 'funcs'
def __init__(self, funcs):
funcs = tuple(reversed(funcs))
self.first = funcs[0]
self.funcs = funcs[1:]
def __call__(self, *args, **kwargs):
ret = self.first(*args, **kwargs)
for f in self.funcs:
ret = f(ret)
return ret
def __getstate__(self):
return self.first, self.funcs
def __setstate__(self, state):
self.first, self.funcs = state
@instanceproperty(classval=__doc__)
def __doc__(self):
def composed_doc(*fs):
"""Generate a docstring for the composition of fs.
"""
if not fs:
# Argument name for the docstring.
return '*args, **kwargs'
return '{f}({g})'.format(f=fs[0].__name__, g=composed_doc(*fs[1:]))
try:
return (
'lambda *args, **kwargs: ' +
composed_doc(*reversed((self.first,) + self.funcs))
)
except AttributeError:
# One of our callables does not have a `__name__`, whatever.
return 'A composition of functions'
@property
def __name__(self):
try:
return '_of_'.join(
(f.__name__ for f in reversed((self.first,) + self.funcs))
)
except AttributeError:
return type(self).__name__
def __repr__(self):
return '{.__class__.__name__}{!r}'.format(
self, tuple(reversed((self.first, ) + self.funcs)))
def __eq__(self, other):
if isinstance(other, Compose):
return other.first == self.first and other.funcs == self.funcs
return NotImplemented
def __ne__(self, other):
equality = self.__eq__(other)
return NotImplemented if equality is NotImplemented else not equality
def __hash__(self):
return hash(self.first) ^ hash(self.funcs)
# Mimic the descriptor behavior of python functions.
# i.e. let Compose be called as a method when bound to a class.
if PY3: # pragma: py2 no cover
# adapted from
# docs.python.org/3/howto/descriptor.html#functions-and-methods
def __get__(self, obj, objtype=None):
return self if obj is None else MethodType(self, obj)
else: # pragma: py3 no cover
# adapted from
# docs.python.org/2/howto/descriptor.html#functions-and-methods
def __get__(self, obj, objtype=None):
return self if obj is None else MethodType(self, obj, objtype)
# introspection with Signature is only possible from py3.3+
if PY3: # pragma: py2 no cover
@instanceproperty
def __signature__(self):
base = inspect.signature(self.first)
last = inspect.signature(self.funcs[-1])
return base.replace(return_annotation=last.return_annotation)
__wrapped__ = instanceproperty(attrgetter('first'))
[docs]def compose(*funcs):
""" Compose functions to operate in series.
Returns a function that applies other functions in sequence.
Functions are applied from right to left so that
``compose(f, g, h)(x, y)`` is the same as ``f(g(h(x, y)))``.
If no arguments are provided, the identity function (f(x) = x) is returned.
>>> inc = lambda i: i + 1
>>> compose(str, inc)(3)
'4'
See Also:
compose_left
pipe
"""
if not funcs:
return identity
if len(funcs) == 1:
return funcs[0]
else:
return Compose(funcs)
[docs]def compose_left(*funcs):
""" Compose functions to operate in series.
Returns a function that applies other functions in sequence.
Functions are applied from left to right so that
``compose_left(f, g, h)(x, y)`` is the same as ``h(g(f(x, y)))``.
If no arguments are provided, the identity function (f(x) = x) is returned.
>>> inc = lambda i: i + 1
>>> compose_left(inc, str)(3)
'4'
See Also:
compose
pipe
"""
return compose(*reversed(funcs))
[docs]def pipe(data, *funcs):
""" Pipe a value through a sequence of functions
I.e. ``pipe(data, f, g, h)`` is equivalent to ``h(g(f(data)))``
We think of the value as progressing through a pipe of several
transformations, much like pipes in UNIX
``$ cat data | f | g | h``
>>> double = lambda i: 2 * i
>>> pipe(3, double, str)
'6'
See Also:
compose
compose_left
thread_first
thread_last
"""
for func in funcs:
data = func(data)
return data
[docs]def complement(func):
""" Convert a predicate function to its logical complement.
In other words, return a function that, for inputs that normally
yield True, yields False, and vice-versa.
>>> def iseven(n): return n % 2 == 0
>>> isodd = complement(iseven)
>>> iseven(2)
True
>>> isodd(2)
False
"""
return compose(operator.not_, func)
[docs]class juxt(object):
""" Creates a function that calls several functions with the same arguments
Takes several functions and returns a function that applies its arguments
to each of those functions then returns a tuple of the results.
Name comes from juxtaposition: the fact of two things being seen or placed
close together with contrasting effect.
>>> inc = lambda x: x + 1
>>> double = lambda x: x * 2
>>> juxt(inc, double)(10)
(11, 20)
>>> juxt([inc, double])(10)
(11, 20)
"""
__slots__ = ['funcs']
def __init__(self, *funcs):
if len(funcs) == 1 and not callable(funcs[0]):
funcs = funcs[0]
self.funcs = tuple(funcs)
def __call__(self, *args, **kwargs):
return tuple(func(*args, **kwargs) for func in self.funcs)
def __getstate__(self):
return self.funcs
def __setstate__(self, state):
self.funcs = state
[docs]def do(func, x):
""" Runs ``func`` on ``x``, returns ``x``
Because the results of ``func`` are not returned, only the side
effects of ``func`` are relevant.
Logging functions can be made by composing ``do`` with a storage function
like ``list.append`` or ``file.write``
>>> from toolz import compose
>>> from toolz.curried import do
>>> log = []
>>> inc = lambda x: x + 1
>>> inc = compose(inc, do(log.append))
>>> inc(1)
2
>>> inc(11)
12
>>> log
[1, 11]
"""
func(x)
return x
[docs]@curry
def flip(func, a, b):
""" Call the function call with the arguments flipped
This function is curried.
>>> def div(a, b):
... return a // b
...
>>> flip(div, 2, 6)
3
>>> div_by_two = flip(div, 2)
>>> div_by_two(4)
2
This is particularly useful for built in functions and functions defined
in C extensions that accept positional only arguments. For example:
isinstance, issubclass.
>>> data = [1, 'a', 'b', 2, 1.5, object(), 3]
>>> only_ints = list(filter(flip(isinstance, int), data))
>>> only_ints
[1, 2, 3]
"""
return func(b, a)
def return_none(exc):
""" Returns None.
"""
return None
[docs]class excepts(object):
"""A wrapper around a function to catch exceptions and
dispatch to a handler.
This is like a functional try/except block, in the same way that
ifexprs are functional if/else blocks.
Examples
--------
>>> excepting = excepts(
... ValueError,
... lambda a: [1, 2].index(a),
... lambda _: -1,
... )
>>> excepting(1)
0
>>> excepting(3)
-1
Multiple exceptions and default except clause.
>>> excepting = excepts((IndexError, KeyError), lambda a: a[0])
>>> excepting([])
>>> excepting([1])
1
>>> excepting({})
>>> excepting({0: 1})
1
"""
def __init__(self, exc, func, handler=return_none):
self.exc = exc
self.func = func
self.handler = handler
def __call__(self, *args, **kwargs):
try:
return self.func(*args, **kwargs)
except self.exc as e:
return self.handler(e)
@instanceproperty(classval=__doc__)
def __doc__(self):
exc = self.exc
try:
if isinstance(exc, tuple):
exc_name = '(%s)' % ', '.join(
map(attrgetter('__name__'), exc),
)
else:
exc_name = exc.__name__
return dedent(
"""\
A wrapper around {inst.func.__name__!r} that will except:
{exc}
and handle any exceptions with {inst.handler.__name__!r}.
Docs for {inst.func.__name__!r}:
{inst.func.__doc__}
Docs for {inst.handler.__name__!r}:
{inst.handler.__doc__}
"""
).format(
inst=self,
exc=exc_name,
)
except AttributeError:
return type(self).__doc__
@property
def __name__(self):
exc = self.exc
try:
if isinstance(exc, tuple):
exc_name = '_or_'.join(map(attrgetter('__name__'), exc))
else:
exc_name = exc.__name__
return '%s_excepting_%s' % (self.func.__name__, exc_name)
except AttributeError:
return 'excepting'
if PY3: # pragma: py2 no cover
def _check_sigspec(sigspec, func, builtin_func, *builtin_args):
if sigspec is None:
try:
sigspec = inspect.signature(func)
except (ValueError, TypeError) as e:
sigspec = e
if isinstance(sigspec, ValueError):
return None, builtin_func(*builtin_args)
elif not isinstance(sigspec, inspect.Signature):
if (
func in _sigs.signatures
and ((
hasattr(func, '__signature__')
and hasattr(func.__signature__, '__get__')
))
): # pragma: no cover (not covered in Python 3.4)
val = builtin_func(*builtin_args)
return None, val
return None, False
return sigspec, None
else: # pragma: py3 no cover
def _check_sigspec(sigspec, func, builtin_func, *builtin_args):
if sigspec is None:
try:
sigspec = inspect.getargspec(func)
except TypeError as e:
sigspec = e
if isinstance(sigspec, TypeError):
if not callable(func):
return None, False
return None, builtin_func(*builtin_args)
return sigspec, None
if PY34 or PYPY: # pragma: no cover
_check_sigspec_orig = _check_sigspec
def _check_sigspec(sigspec, func, builtin_func, *builtin_args):
# Python 3.4 and PyPy may lie, so use our registry for builtins instead
if func in _sigs.signatures:
val = builtin_func(*builtin_args)
return None, val
return _check_sigspec_orig(sigspec, func, builtin_func, *builtin_args)
_check_sigspec.__doc__ = """ \
Private function to aid in introspection compatibly across Python versions.
If a callable doesn't have a signature (Python 3) or an argspec (Python 2),
the signature registry in toolz._signatures is used.
"""
if PY3: # pragma: py2 no cover
def num_required_args(func, sigspec=None):
sigspec, rv = _check_sigspec(sigspec, func, _sigs._num_required_args,
func)
if sigspec is None:
return rv
return sum(1 for p in sigspec.parameters.values()
if p.default is p.empty
and p.kind in (p.POSITIONAL_OR_KEYWORD, p.POSITIONAL_ONLY))
def has_varargs(func, sigspec=None):
sigspec, rv = _check_sigspec(sigspec, func, _sigs._has_varargs, func)
if sigspec is None:
return rv
return any(p.kind == p.VAR_POSITIONAL
for p in sigspec.parameters.values())
def has_keywords(func, sigspec=None):
sigspec, rv = _check_sigspec(sigspec, func, _sigs._has_keywords, func)
if sigspec is None:
return rv
return any(p.default is not p.empty
or p.kind in (p.KEYWORD_ONLY, p.VAR_KEYWORD)
for p in sigspec.parameters.values())
def is_valid_args(func, args, kwargs, sigspec=None):
sigspec, rv = _check_sigspec(sigspec, func, _sigs._is_valid_args,
func, args, kwargs)
if sigspec is None:
return rv
try:
sigspec.bind(*args, **kwargs)
except TypeError:
return False
return True
def is_partial_args(func, args, kwargs, sigspec=None):
sigspec, rv = _check_sigspec(sigspec, func, _sigs._is_partial_args,
func, args, kwargs)
if sigspec is None:
return rv
try:
sigspec.bind_partial(*args, **kwargs)
except TypeError:
return False
return True
else: # pragma: py3 no cover
def num_required_args(func, sigspec=None):
sigspec, rv = _check_sigspec(sigspec, func, _sigs._num_required_args,
func)
if sigspec is None:
return rv
num_defaults = len(sigspec.defaults) if sigspec.defaults else 0
return len(sigspec.args) - num_defaults
def has_varargs(func, sigspec=None):
sigspec, rv = _check_sigspec(sigspec, func, _sigs._has_varargs, func)
if sigspec is None:
return rv
return sigspec.varargs is not None
def has_keywords(func, sigspec=None):
sigspec, rv = _check_sigspec(sigspec, func, _sigs._has_keywords, func)
if sigspec is None:
return rv
return sigspec.defaults is not None or sigspec.keywords is not None
def is_valid_args(func, args, kwargs, sigspec=None):
sigspec, rv = _check_sigspec(sigspec, func, _sigs._is_valid_args,
func, args, kwargs)
if sigspec is None:
return rv
spec = sigspec
defaults = spec.defaults or ()
num_pos = len(spec.args) - len(defaults)
missing_pos = spec.args[len(args):num_pos]
if any(arg not in kwargs for arg in missing_pos):
return False
if spec.varargs is None:
num_extra_pos = max(0, len(args) - num_pos)
else:
num_extra_pos = 0
kwargs = dict(kwargs)
# Add missing keyword arguments (unless already included in `args`)
missing_kwargs = spec.args[num_pos + num_extra_pos:]
kwargs.update(zip(missing_kwargs, defaults[num_extra_pos:]))
# Convert call to use positional arguments
args = args + tuple(kwargs.pop(key) for key in spec.args[len(args):])
if (
not spec.keywords and kwargs
or not spec.varargs and len(args) > len(spec.args)
or set(spec.args[:len(args)]) & set(kwargs)
):
return False
else:
return True
def is_partial_args(func, args, kwargs, sigspec=None):
sigspec, rv = _check_sigspec(sigspec, func, _sigs._is_partial_args,
func, args, kwargs)
if sigspec is None:
return rv
spec = sigspec
defaults = spec.defaults or ()
num_pos = len(spec.args) - len(defaults)
if spec.varargs is None:
num_extra_pos = max(0, len(args) - num_pos)
else:
num_extra_pos = 0
kwargs = dict(kwargs)
# Add missing keyword arguments (unless already included in `args`)
missing_kwargs = spec.args[num_pos + num_extra_pos:]
kwargs.update(zip(missing_kwargs, defaults[num_extra_pos:]))
# Add missing position arguments as keywords (may already be in kwargs)
missing_args = spec.args[len(args):num_pos + num_extra_pos]
kwargs.update((x, None) for x in missing_args)
# Convert call to use positional arguments
args = args + tuple(kwargs.pop(key) for key in spec.args[len(args):])
if (
not spec.keywords and kwargs
or not spec.varargs and len(args) > len(spec.args)
or set(spec.args[:len(args)]) & set(kwargs)
):
return False
else:
return True
def is_arity(n, func, sigspec=None):
""" Does a function have only n positional arguments?
This function relies on introspection and does not call the function.
Returns None if validity can't be determined.
>>> def f(x):
... return x
>>> is_arity(1, f)
True
>>> def g(x, y=1):
... return x + y
>>> is_arity(1, g)
False
"""
sigspec, rv = _check_sigspec(sigspec, func, _sigs._is_arity, n, func)
if sigspec is None:
return rv
num = num_required_args(func, sigspec)
if num is not None:
num = num == n
if not num:
return False
varargs = has_varargs(func, sigspec)
if varargs:
return False
keywords = has_keywords(func, sigspec)
if keywords:
return False
if num is None or varargs is None or keywords is None: # pragma: no cover
return None
return True
num_required_args.__doc__ = """ \
Number of required positional arguments
This function relies on introspection and does not call the function.
Returns None if validity can't be determined.
>>> def f(x, y, z=3):
... return x + y + z
>>> num_required_args(f)
2
>>> def g(*args, **kwargs):
... pass
>>> num_required_args(g)
0
"""
has_varargs.__doc__ = """ \
Does a function have variadic positional arguments?
This function relies on introspection and does not call the function.
Returns None if validity can't be determined.
>>> def f(*args):
... return args
>>> has_varargs(f)
True
>>> def g(**kwargs):
... return kwargs
>>> has_varargs(g)
False
"""
has_keywords.__doc__ = """ \
Does a function have keyword arguments?
This function relies on introspection and does not call the function.
Returns None if validity can't be determined.
>>> def f(x, y=0):
... return x + y
>>> has_keywords(f)
True
"""
is_valid_args.__doc__ = """ \
Is ``func(*args, **kwargs)`` a valid function call?
This function relies on introspection and does not call the function.
Returns None if validity can't be determined.
>>> def add(x, y):
... return x + y
>>> is_valid_args(add, (1,), {})
False
>>> is_valid_args(add, (1, 2), {})
True
>>> is_valid_args(map, (), {})
False
**Implementation notes**
Python 2 relies on ``inspect.getargspec``, which only works for
user-defined functions. Python 3 uses ``inspect.signature``, which
works for many more types of callables.
Many builtins in the standard library are also supported.
"""
is_partial_args.__doc__ = """ \
Can partial(func, *args, **kwargs)(*args2, **kwargs2) be a valid call?
Returns True *only* if the call is valid or if it is possible for the
call to become valid by adding more positional or keyword arguments.
This function relies on introspection and does not call the function.
Returns None if validity can't be determined.
>>> def add(x, y):
... return x + y
>>> is_partial_args(add, (1,), {})
True
>>> is_partial_args(add, (1, 2), {})
True
>>> is_partial_args(add, (1, 2, 3), {})
False
>>> is_partial_args(map, (), {})
True
**Implementation notes**
Python 2 relies on ``inspect.getargspec``, which only works for
user-defined functions. Python 3 uses ``inspect.signature``, which
works for many more types of callables.
Many builtins in the standard library are also supported.
"""
from . import _signatures as _sigs