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cirq.num_qubits

Returns the number of qubits, qudits, or qids val operates on.

cirq.num_qubits(
    val: Any, default: TDefault = RaiseTypeErrorIfNotProvidedInt
) -> (int | TDefault)

Used in the tutorials
Custom Transformers

Args
`val`	The value to get the number of qubits from.
`default`	Determines the fallback behavior when `val` doesn't have a number of qubits. If `default` is not set, a TypeError is raised. If default is set to a value, that value is returned.

Returns
If `val` has a `_num_qubits_` method and its result is not NotImplemented, that result is returned. Otherwise, if `val` has a `_qid_shape_` method, the number of qubits is computed from the length of the shape and returned e.g. `len(shape)`. If neither method returns a value other than NotImplemented and a default value was specified, the default value is returned.

Raises
`TypeError`	`val` doesn't have either a `_num_qubits_` or a `_qid_shape_` method (or they returned NotImplemented) and also no default value was specified.

Args