Avoid getting NumPy dtypes in printed (string) scalar values

As a consequence of [NEP
51](https://numpy.org/neps/nep-0051-scalar-representation.html#nep51),
the string representation of scalar numbers changed in NumPy 2 to
include type information. This affected printing Cirq circuit
diagrams: instead seeing numbers like 1.5, you would see
`np.float64(1.5)` and similar.

The solution is to avoid getting the repr output of NumPy scalars
directly, and instead doing `.item()` on them before passing them
to `format()` or other string-producing functions.

cirq-core/cirq/_compat.py

@@ -192,6 +192,9 @@ def _print(self, expr, **kwargs):
     if hasattr(value, "__qualname__"):
         return f"{value.__module__}.{value.__qualname__}"
 
+    if isinstance(value, np.number):
+        return repr(value.item())
+
     return repr(value)
 
 

cirq-core/cirq/ops/fsim_gate.py

@@ -23,7 +23,7 @@
 
 import cmath
 import math
-from typing import AbstractSet, Any, Dict, Iterator, Optional, Tuple
+from typing import AbstractSet, Any, Dict, Iterator, Optional, Tuple, Union
 
 import numpy as np
 import sympy
@@ -52,6 +52,12 @@ def _half_pi_mod_pi(param: 'cirq.TParamVal') -> bool:
     return param in (-np.pi / 2, np.pi / 2, -sympy.pi / 2, sympy.pi / 2)
 
 
+def _plainvalue(value: Union[int, float, complex, np.number]) -> Union[int, float, complex]:
+    """Returns a plain Python number if the given value is a NumPy number.
+    Used to avoid a change in repr behavior introduced in NumPy 2."""
+    return value.item() if isinstance(value, np.number) else value
+
+
 @value.value_equality(approximate=True)
 class FSimGate(gate_features.InterchangeableQubitsGate, raw_types.Gate):
     r"""Fermionic simulation gate.
@@ -196,8 +202,8 @@ def _decompose_(self, qubits) -> Iterator['cirq.OP_TREE']:
         yield cirq.CZ(a, b) ** (-self.phi / np.pi)
 
     def _circuit_diagram_info_(self, args: 'cirq.CircuitDiagramInfoArgs') -> Tuple[str, ...]:
-        t = args.format_radians(self.theta)
-        p = args.format_radians(self.phi)
+        t = args.format_radians(_plainvalue(self.theta))
+        p = args.format_radians(_plainvalue(self.phi))
         return f'FSim({t}, {p})', f'FSim({t}, {p})'
 
     def __pow__(self, power) -> 'FSimGate':
@@ -476,11 +482,11 @@ def to_exponent(angle_rads: 'cirq.TParamVal') -> 'cirq.TParamVal':
         yield cirq.Z(q1) ** to_exponent(after[1])
 
     def _circuit_diagram_info_(self, args: 'cirq.CircuitDiagramInfoArgs') -> Tuple[str, ...]:
-        theta = args.format_radians(self.theta)
-        zeta = args.format_radians(self.zeta)
-        chi = args.format_radians(self.chi)
-        gamma = args.format_radians(self.gamma)
-        phi = args.format_radians(self.phi)
+        theta = args.format_radians(_plainvalue(self.theta))
+        zeta = args.format_radians(_plainvalue(self.zeta))
+        chi = args.format_radians(_plainvalue(self.chi))
+        gamma = args.format_radians(_plainvalue(self.gamma))
+        phi = args.format_radians(_plainvalue(self.phi))
         return (
             f'PhFSim({theta}, {zeta}, {chi}, {gamma}, {phi})',
             f'PhFSim({theta}, {zeta}, {chi}, {gamma}, {phi})',

cirq-core/cirq/protocols/circuit_diagram_info_protocol.py

@@ -245,6 +245,8 @@ def __repr__(self) -> str:
     def format_real(self, val: Union[sympy.Basic, int, float]) -> str:
         if isinstance(val, sympy.Basic):
             return str(val)
+        if isinstance(val, np.number):
+            val = val.item()
         if val == int(val):
             return str(int(val))
         if self.precision is None: