def test_piecewise_expressions():
"""test special expressions for creating fields"""
grid = CartesianGrid([[0, 4]], 32)
field = ScalarField.from_expression(grid,
"Piecewise((x**2, x>2), (1+x, x<=2))")
x = grid.axes_coords[0]
field_data = np.piecewise(x, [x > 2, x <= 2],
[lambda x: x**2, lambda x: 1 + x])
np.testing.assert_allclose(field.data, field_data)
def test_interpolation_after_free():
"""test whether interpolation is possible when the original field is removed"""
f = ScalarField.from_expression(UnitGrid([5]), "x")
intp = f.make_interpolator(backend="numba")
# delete original field
del f
gc.collect()
# hope that this overwrites the memory
f = ScalarField.random_uniform(UnitGrid([5]))
assert intp(np.array([2.3])) == pytest.approx(2.3)
def test_from_expression():
"""test creating scalar field from expression"""
grid = UnitGrid([1, 2])
sf = ScalarField.from_expression(grid, "x * y", label="abc")
assert sf.label == "abc"
np.testing.assert_allclose(sf.data, [[0.25, 0.75]])