ruff - check and fix escape-sequence-in-docstring (#7670)

- ruff - activate D301 - escape-sequence-in-docstring

- Fix escape sequences in docstrings, e.g., switch to raw
  docstrings when we need literal backslash.

Partially implements #7505

Author: pavoljuhas

cirq-core/cirq/devices/grid_qubit.py

@@ -285,7 +285,7 @@ def rect(rows: int, cols: int, top: int = 0, left: int = 0, *, dimension: int) -
 
     @staticmethod
     def from_diagram(diagram: str, dimension: int) -> list[GridQid]:
-        """Parse ASCII art device layout into a device.
+        r"""Parse ASCII art device layout into a device.
 
         As an example, the below diagram will create a list of GridQid in a
         pyramid structure.
@@ -322,7 +322,7 @@ def from_diagram(diagram: str, dimension: int) -> list[GridQid]:
                 a row. Alphanumeric characters are assigned as qid.
                 Dots ('.'), dashes ('-'), and spaces (' ') are treated as
                 empty locations in the grid. If diagram has characters other
-                than alphanumerics, spacers, and newlines ('\\n'), an error will
+                than alphanumerics, spacers, and newlines ('\n'), an error will
                 be thrown. The top-left corner of the diagram will be have
                 coordinate (0, 0).
 
@@ -439,7 +439,7 @@ def rect(rows: int, cols: int, top: int = 0, left: int = 0) -> list[GridQubit]:
 
     @staticmethod
     def from_diagram(diagram: str) -> list[GridQubit]:
-        """Parse ASCII art into device layout info.
+        r"""Parse ASCII art into device layout info.
 
         As an example, the below diagram will create a list of
         GridQubit in a pyramid structure.
@@ -476,7 +476,7 @@ def from_diagram(diagram: str) -> list[GridQubit]:
                 a row. Alphanumeric characters are assigned as qid.
                 Dots ('.'), dashes ('-'), and spaces (' ') are treated as
                 empty locations in the grid. If diagram has characters other
-                than alphanumerics, spacers, and newlines ('\\n'), an error will
+                than alphanumerics, spacers, and newlines ('\n'), an error will
                 be thrown. The top-left corner of the diagram will be have
                 coordinate (0,0).
 
@@ -503,7 +503,7 @@ def _json_dict_(self) -> dict[str, Any]:
 
 
 def _ascii_diagram_to_coords(diagram: str) -> list[tuple[int, int]]:
-    """Parse ASCII art device layout into info about qids coordinates
+    r"""Parse ASCII art device layout into info about qids coordinates
 
     Args:
         diagram: String representing the qid layout. Each line represents

cirq-core/cirq/linalg/decompositions.py

@@ -243,7 +243,7 @@ def so4_to_magic_su2s(
 
 @value.value_equality(approximate=True)
 class AxisAngleDecomposition:
-    """Represents a unitary operation as an axis, angle, and global phase.
+    r"""Represents a unitary operation as an axis, angle, and global phase.
 
     The unitary $U$ is decomposed as follows:
 

cirq-core/cirq/ops/named_qubit.py

@@ -148,7 +148,7 @@ def __str__(self) -> str:
 
     @staticmethod
     def range(*args, prefix: str, dimension: int) -> list[NamedQid]:
-        """Returns a range of ``NamedQid``\\s.
+        """Returns a range of ``NamedQid``s.
 
         The range returned starts with the prefix, and followed by a qid for
         each number in the range, e.g.:
@@ -166,7 +166,7 @@ def range(*args, prefix: str, dimension: int) -> list[NamedQid]:
             dimension: The dimension of the qid's Hilbert space, i.e.
                 the number of quantum levels.
         Returns:
-            A list of ``NamedQid``\\s.
+            A list of ``NamedQid``s.
         """
         return [NamedQid(f"{prefix}{i}", dimension=dimension) for i in range(*args)]
 

cirq-core/cirq/vis/density_matrix.py

@@ -84,7 +84,7 @@ def plot_density_matrix(
     show_text: bool = False,
     title: str | None = None,
 ) -> plt.Axes:
-    """Generates a plot for a given density matrix.
+    r"""Generates a plot for a given density matrix.
 
     1. Each entry of the density matrix, a complex number, is plotted as an
     Argand Diagram where the partially filled red circle represents the magnitude

examples/stabilizer_code.py

@@ -322,7 +322,7 @@ def correct(self, qubits: list[cirq.Qid], ancillas: list[cirq.Qid]) -> cirq.Circ
         return circuit
 
     def decode(self, qubits: list[cirq.Qid], ancillas: list[cirq.Qid], state_vector) -> list[int]:
-        """Computes the output of the circuit by projecting onto the \bar{Z}.
+        r"""Computes the output of the circuit by projecting onto the \bar{Z}.
 
         Args:
             qubits: the qubits where the (now corrected) code words are stored.

pyproject.toml

@@ -74,6 +74,7 @@ select = [
              # pylint expression-not-assigned, pointless-exception-statement,
              # pointless-statement, pointless-string-statement
     "B033",  # duplicate-value, pylint duplicate-value
+    "D301",  # escape-sequence-in-docstring
     "D419",  # empty-docstring, pylint empty-docstring
     "E402",  # module-import-not-at-top-of-file, pylint wrong-import-position
     "E501",  # line-too-long, pylint line-too-long