cirq.Ry complains that it needs one argument

Question

When I try to put an Ry gate into my circuit in cirq, I get an error saying that it only takes one argument.

import cirq
import numpy as np
q = cirq.LineQubit(0)
cirq.Circuit(cirq.Ry(np.pi / 2, q))

TypeError: Ry() takes 1 positional argument but 2 were given

Answer 1

cirq.Ry is a method that, given an angle, returns a gate. You then apply the gate to a qubit:

cirq.Ry(angle).on(qubit)

or, equivalently but a bit more confusingly:

cirq.Ry(angle)(qubit)