[py symbolic] SymPy conversion supports integers (#20415)

bindings/pydrake/symbolic/_symbolic_extra.py

@@ -30,10 +30,10 @@ def _reduce_mul(*args):
 
 
 def to_sympy(
-    x: typing.Union[float, bool, Variable, Expression, Formula],
+    x: typing.Union[float, int, bool, Variable, Expression, Formula],
     *,
     memo: typing.Dict = None
-) -> typing.Union[float, bool, "sympy.Expr"]:
+) -> typing.Union[float, int, bool, "sympy.Expr"]:
     """Converts a pydrake object to the corresponding SymPy Expr.
 
     Certain expressions are not supported and will raise NotImplementedError.
@@ -63,10 +63,10 @@ def to_sympy(
 
 
 def from_sympy(
-    x: typing.Union[float, bool, "sympy.Expr"],
+    x: typing.Union[float, int, bool, "sympy.Expr"],
     *,
     memo: typing.Dict = None
-) -> typing.Union[float, bool, Variable, Expression, Formula]:
+) -> typing.Union[float, int, bool, Variable, Expression, Formula]:
     """Converts a SymPy Expr to the corresponding pydrake object.
 
     Certain expressions are not supported and will raise NotImplementedError.

bindings/pydrake/symbolic/_symbolic_sympy.py

@@ -129,16 +129,16 @@ def _var_from_sympy(sympy_var: sympy.Dummy, *, memo: Dict):
 
 
 def _to_sympy(
-    x: Union[float, bool, Variable, Expression, Formula],
+    x: Union[float, int, bool, Variable, Expression, Formula],
     *,
     memo: Dict = None
-) -> Union[float, bool, sympy.Expr]:
+) -> Union[float, int, bool, sympy.Expr]:
     """This is the private implementation of pydrake.symbolic.to_sympy().
     Refer to that module-level function for the full docstring.
 
     TODO(jwnimmer-tri) Also support Polynomial, Monomial, etc.
     """
-    if isinstance(x, (float, bool)):
+    if isinstance(x, (float, int, bool)):
         return x
     if isinstance(x, Variable):
         return _var_to_sympy(drake_var=x, memo=memo)
@@ -222,15 +222,15 @@ def _lambdify(*, expr, args):
 
 
 def _from_sympy(
-    x: Union[float, bool, sympy.Expr],
+    x: Union[float, int, bool, sympy.Expr],
     *,
     memo: Dict = None
-) -> Union[float, bool, Variable, Expression, Formula]:
+) -> Union[float, int, bool, Variable, Expression, Formula]:
     """This is the private implementation of pydrake.symbolic.from_sympy().
     Refer to that module-level function for the full docstring.
     """
     # Return non-SymPy inputs as-is.
-    if isinstance(x, (float, bool)):
+    if isinstance(x, (float, int, bool)):
         return x
     # Return constants quickly.
     if x.is_number:

bindings/pydrake/symbolic/test/sympy_test.py

@@ -22,6 +22,7 @@ def test_round_trip(self):
         q, r = [Variable(name, BOOLEAN) for name in "q r".split()]
         inputs = [
             # Constants.
+            1,
             1.0,
             np.nan,
             Expression(1.0),
@@ -99,7 +100,7 @@ def _test_one_round_trip(self, item):
         readback = mut.from_sympy(converted, memo=memo)
 
         # When the input was a built-in type, np.testing works well.
-        if isinstance(item, (float, bool)):
+        if isinstance(item, (float, int, bool)):
             np.testing.assert_equal(item, readback)
             return
 
@@ -120,7 +121,7 @@ def _test_one_round_trip(self, item):
                   f"{readback_str} (from {converted_str})")
 
     def _test_one_eval(self, item):
-        if isinstance(item, (float, bool, Variable)):
+        if isinstance(item, (float, int, bool, Variable)):
             # Skip this case. Evaluation is not particularly interesting.
             return