def __getitem__(self, value) -> State:
"""Return the ionic fraction(s)."""
if isinstance(value, slice):
raise TypeError("IonizationState instances cannot be sliced.")
if isinstance(value,
(int, np.integer)) and 0 <= value <= self.atomic_number:
result = State(value, self.ionic_fractions[value],
self.ionic_symbols[value])
else:
if not isinstance(value, Particle):
try:
value = Particle(value)
except InvalidParticleError as exc:
raise InvalidParticleError(
f"{value} is not a valid integer charge or "
f"particle.") from exc
same_element = value.element == self.element
same_isotope = value.isotope == self.isotope
has_charge_info = value.is_category(
any_of=["charged", "uncharged"])
if same_element and same_isotope and has_charge_info:
Z = value.integer_charge
result = State(Z, self.ionic_fractions[Z],
self.ionic_symbols[Z])
else:
if not same_element or not same_isotope:
raise AtomicError("Inconsistent element or isotope.")
elif not has_charge_info:
raise ChargeError("No integer charge provided.")
return result
def is_stable(particle: Particle,
mass_numb: Optional[numbers.Integral] = None) -> bool:
"""
Return `True` for stable isotopes and particles and `False` for
unstable isotopes.
Parameters
----------
particle: `int`, `str`, or `~plasmapy.atomic.Particle`
A string representing an isotope or particle, or an integer
representing an atomic number.
mass_numb: `int`, optional
The mass number of the isotope.
Returns
-------
is_stable: `bool`
`True` if the isotope is stable, `False` if it is unstable.
Raises
------
`~plasmapy.utils.InvalidIsotopeError`
If the arguments correspond to a valid element but not a
valid isotope.
`~plasmapy.utils.InvalidParticleError`
If the arguments do not correspond to a valid particle.
`TypeError`
If the argument is not a `str` or `int`.
`~plasmapy.utils.MissingAtomicDataError`
If stability information is not available.
Examples
--------
>>> is_stable("H-1")
True
>>> is_stable("tritium")
False
>>> is_stable("e-")
True
>>> is_stable("tau+")
False
"""
if particle.element and not particle.isotope:
raise InvalidIsotopeError(
"The input to is_stable must be either an isotope or a special particle."
)
return particle.is_category('stable')
