More efficient conversion from Python int to fmpz

[oscarbenjamin]

It looks like Python 3.13 will provide public C API for efficiently converting to and from a PyLong. These should be compatible with mpz_import/mpz_export rather than converting between hex strings:

python/cpython#121339

python-flint/src/flint/types/fmpz.pxd

Lines 15 to 23 in 430b8e5

	cdef inline int fmpz_set_pylong(fmpz_t x, obj):
	cdef int overflow
	cdef slong longval
	longval = pylong_as_slong(<PyObject*>obj, &overflow)
	if overflow:
	s = "%x" % obj
	fmpz_set_str(x, chars_from_str(s), 16)
	else:
	fmpz_set_si(x, longval)

python-flint/src/flint/types/fmpz.pyx

Lines 16 to 27 in 430b8e5

	cdef fmpz_get_intlong(fmpz_t x):
	"""
	Convert fmpz_t to a Python int or long.
	"""
	cdef char * s
	if COEFF_IS_MPZ(x[0]):
	s = fmpz_get_str(NULL, 16, x)
	v = int(str_from_chars(s), 16)
	libc.stdlib.free(s)
	return v
	else:
	return <slong>x[0]

[skirpichev]

It looks like Python 3.13 will provide public C API

Nit: 3.14. Maybe.