replace custom @require_keywords decorator with modern syntax

periodictable/formulas.py

@@ -14,7 +14,7 @@
 
 from .core import default_table, isatom, isisotope, ision, change_table
 from .constants import avogadro_number
-from .util import require_keywords, cell_volume
+from .util import cell_volume
 
 PACKING_FACTORS = dict(cubic=pi/6, bcc=pi*sqrt(3)/8, hcp=pi/sqrt(18),
                        fcc=pi/sqrt(18), diamond=pi*sqrt(3)/16)
@@ -518,8 +518,7 @@ def volume(self, *args, **kw):
             packing_factor = PACKING_FACTORS[packing_factor.lower()]
         return V/packing_factor*1e-24
 
-    @require_keywords
-    def neutron_sld(self, wavelength=None, energy=None):
+    def neutron_sld(self, *, wavelength=None, energy=None):
         """
         Neutron scattering information for the molecule.
 
@@ -543,8 +542,7 @@ def neutron_sld(self, wavelength=None, energy=None):
         return neutron_sld(self.atoms, density=self.density,
                            wavelength=wavelength, energy=energy)
 
-    @require_keywords
-    def xray_sld(self, energy=None, wavelength=None):
+    def xray_sld(self, *, energy=None, wavelength=None):
         """
         X-ray scattering length density for the molecule.
 

periodictable/nsf.py

@@ -188,7 +188,7 @@
 from .core import Element, Isotope, default_table
 from .constants import (avogadro_number, planck_constant, electron_volt,
                         neutron_mass, atomic_mass_constant)
-from .util import require_keywords, parse_uncertainty
+from .util import parse_uncertainty
 
 __all__ = ['init', 'Neutron',
            'neutron_energy', 'neutron_wavelength',
@@ -483,8 +483,7 @@ def scattering_by_wavelength(self, wavelength):
         sigma_s = _4PI_100*abs(b_c)**2 # 1 barn = 1 fm^2 1e-2 barn/fm^2
         return b_c, sigma_s
 
-    @require_keywords
-    def sld(self, wavelength=ABSORPTION_WAVELENGTH):
+    def sld(self, *, wavelength=ABSORPTION_WAVELENGTH):
         r"""
         Returns scattering length density for the element at natural
         abundance and density.
@@ -505,8 +504,7 @@ def sld(self, wavelength=ABSORPTION_WAVELENGTH):
             return None, None, None
         return self.scattering(wavelength=wavelength)[0]
 
-    @require_keywords
-    def scattering(self, wavelength=ABSORPTION_WAVELENGTH):
+    def scattering(self, *, wavelength=ABSORPTION_WAVELENGTH):
         r"""
         Returns neutron scattering information for the element at natural
         abundance and density.
@@ -650,8 +648,7 @@ def init(table, reload=False):
 # TODO: split incoherent into spin and isotope incoherence (eq 17-19 of Sears)
 # TODO: require parsed compound rather than including formula() keywords in api
 # Note: docs and function prototype are reproduced in __init__
-@require_keywords
-def neutron_scattering(compound, density=None,
+def neutron_scattering(compound, *, density=None,
                        wavelength=None, energy=None,
                        natural_density=None, table=None):
     r"""

periodictable/util.py

@@ -91,74 +91,3 @@ def cell_volume(a=None, b=None, c=None, alpha=None, beta=None, gamma=None):
     cgamma = cos(radians(gamma)) if gamma is not None else calpha
     V = a*b*c*sqrt(1 - calpha**2 - cbeta**2 - cgamma**2 + 2*calpha*cbeta*cgamma)
     return V
-
-def require_keywords(function):
-    r"""
-    Decorator which forces all keyword arguments to the function to be
-    explicitly named.
-
-    For example:
-
-        >>> @require_keywords
-        ... def fn(a, b, c=3): pass
-        >>> fn(1, 2, 3)
-        Traceback (most recent call last):
-        ...
-        TypeError: name=value required for c
-        >>> fn(1, 2, c=6)
-        >>> fn(b=1, a=2, c=6)
-
-    Variable arguments are not currently supported:
-
-        >>> @require_keywords
-        ... def fn(a, b, c=6, *args, **kw): pass
-        Traceback (most recent call last):
-        ...
-        NotImplementedError: only named arguments for now
-
-    .. Note:: The call signature is not preserved.
-
-    We can't preserve the function signature for the call since the only
-    way we can count the number of non-keyword arguments is to
-    use the \*args, \*\*kw call style.  Python 3+ provides the '\*' call
-    signature element which will force all keywords after '\*' to be named.
-    """
-    import functools
-    try:
-        from inspect import signature
-        getargspec = _getargspec_from_signature
-    except ImportError: # CRUFT: py 2.7 support
-        from inspect import getargspec
-
-    args, vararg, varkwd, defaults = getargspec(function)
-    if defaults is None:
-        defaults = []
-    named_args = args[:-len(defaults)]
-    named_kwds = args[-len(defaults):]
-    # Keep it simple for now
-    if vararg or varkwd:
-        raise NotImplementedError("only named arguments for now")
-    @functools.wraps(function)
-    def _require_kwds(*args, **kw):
-        if len(args) > len(named_args):
-            raise TypeError("name=value required for "+", ".join(named_kwds))
-        return function(*args, **kw)
-    return _require_kwds
-
-def _getargspec_from_signature(function):
-    """
-    Reproduce getargspec() interface using newer signature protocol
-    """
-    from inspect import signature
-
-    args, vararg, varkwd, defaults = [], None, None, []
-    sig = signature(function)
-    for p in sig.parameters.values():
-        args.append(p.name)
-        if p.default is not p.empty:
-            defaults.append(p.default)
-        if p.kind is p.VAR_POSITIONAL:
-            vararg = p.name
-        elif p.kind is p.VAR_KEYWORD:
-            varkwd = p.name
-    return args, vararg, varkwd, defaults

periodictable/xsf.py

@@ -193,7 +193,6 @@
 from .constants import (
     avogadro_number, planck_constant, speed_of_light, electron_volt,
     electron_radius)
-from .util import require_keywords
 
 def xray_wavelength(energy):
     r"""
@@ -271,8 +270,7 @@ def _gettable(self):
         return self._table
     sftable = property(_gettable, doc="X-ray scattering factor table (E,f1,f2)")
 
-    @require_keywords
-    def scattering_factors(self, energy=None, wavelength=None):
+    def scattering_factors(self, *, energy=None, wavelength=None):
         """
         X-ray scattering factors f', f''.
 
@@ -337,8 +335,7 @@ def f0(self, Q):
                                 charge=self.element.charge)
         return f
 
-    @require_keywords
-    def sld(self, wavelength=None, energy=None):
+    def sld(self, *, wavelength=None, energy=None):
         r"""
         X ray scattering length density.
 
@@ -382,8 +379,7 @@ def sld(self, wavelength=None, energy=None):
         return rho, irho
 
 # Note: docs and function prototype are reproduced in __init__
-@require_keywords
-def xray_sld(compound, density=None, natural_density=None,
+def xray_sld(compound, *, density=None, natural_density=None,
              wavelength=None, energy=None):
     """
     Compute xray scattering length densities for molecules.
@@ -435,8 +431,7 @@ def xray_sld(compound, density=None, natural_density=None,
     return rho, irho
 
 
-@require_keywords
-def index_of_refraction(compound, density=None, natural_density=None,
+def index_of_refraction(compound, *, density=None, natural_density=None,
                         energy=None, wavelength=None):
     """
     Calculates the index of refraction for a given compound
@@ -470,8 +465,7 @@ def index_of_refraction(compound, density=None, natural_density=None,
                       wavelength=wavelength)
     return 1 - wavelength**2/(2*pi)*(f1 + f2*1j)*1e-6
 
-@require_keywords
-def mirror_reflectivity(compound, density=None, natural_density=None,
+def mirror_reflectivity(compound, *, density=None, natural_density=None,
                         energy=None, wavelength=None,
                         angle=None, roughness=0):
     """