How to properly check if a variable is PolyLike?

[iyanmv]

Hello,

How can we check if a variable is PolyLike?

First I tried to wrap my code with a try statement.

import galois

try:
    poly = galois.Poly(provided_poly_like)

except ValueError, TypeError:
    pass

But this fails if provided_poly_like is already a Poly. For example,

>>> galois.Poly(galois.conway_poly(2, 12))
TypeError: Argument 'coeffs' must be an instance of (<class 'list'>, <class 'tuple'>, <class 'numpy.ndarray'>, <class 'galois.Array'>), not <class 'galois.Poly'>.

So later I tried using isinstance and I found some stackoverflow questions about checking Union types at runtime, but probably I'm doing something wrong. What I tried is:

assert isinstance(provided_poly_like, galois.typing.PolyLike.__args__)

[mhostetter]

I have a private constructor that converts PolyLike into Poly. I found it useful in the internal library code. At one point I considered making it a public constructor. I also toyed with the idea of making galois.Poly() accept PolyLike.

What are you thoughts? Is this what you're looking for? By the way, the type checking if very rudimentary. I've been looking for an easier way to runtime type check using type annotations, but every solution I've found has been shoddy.

galois/src/galois/_polys/_poly.py

Lines 130 to 149 in a140a46

	def _PolyLike(cls, poly_like: PolyLike, field: Type[Array] | None = None) -> Self:
	"""
	A private alternate constructor that converts a poly-like object into a polynomial, given a finite field.
	"""
	if isinstance(poly_like, int):
	poly = Poly.Int(poly_like, field=field)
	elif isinstance(poly_like, str):
	poly = Poly.Str(poly_like, field=field)
	elif isinstance(poly_like, (tuple, list, np.ndarray)):
	poly = Poly(poly_like, field=field)
	elif isinstance(poly_like, Poly):
	poly = poly_like
	else:
	raise TypeError(
	f"A 'poly-like' object must be an int, str, tuple, list, np.ndarray, or galois.Poly, "
	f"not {type(poly_like)}."
	)
	return poly

[iyanmv]

Yes, exactly what I was looking for, thanks! I missed it when searching the code 😅

And yes, I think it would be nice idea to make galois.Poly() accept PolyLike, or at least Poly in addition to what is already supported.

I would expect these two examples to work in the same way.

from galois import GF2, Poly

array = GF2.Random(10)
new_array = GF2(array)  # Ok, we get a copy

poly = Poly.Str("x + 1")
new_poly = Poly(poly)  # This fails, but I think it should be Ok as well

[mhostetter]

Yeah, that's easy enough to do. If we make Poly() accept PolyLike, then we should probably remove Poly.Int() and Poly.Str(). If you'd like to write up an issue, then we can track it.