Fix length computation sympy (#770)

* use scipy for advanced integration methods inside MathematicalExpression. Fixes #725
* catch UnitStrippedWarning as it is expected during this kind of computation.
* try to use both modules (get rid of deprecationwarnings)

* Silence DeepSource
Co-authored-by: vhirtham <20574817+vhirtham@users.noreply.github.com>

CHANGELOG.rst

@@ -2,6 +2,16 @@
  Release Notes
 ###############
 
+********************
+ 0.6.2 (tba)
+********************
+
+fixes
+=====
+
+-  `MathematicalExpression` now uses SciPy and NumPy in numerical function evaluation. This enables it to use
+   advanced integration methods and fixes lengths computation of `DynamicShapeSegment` [:pull:`770`].
+
 ********************
  0.6.1 (19.05.2022)
 ********************

weldx/core.py

@@ -56,7 +56,7 @@ def __init__(
         self._expression: sympy.Expr = expression
 
         self.function = sympy.lambdify(
-            tuple(self._expression.free_symbols), self._expression, "numpy"
+            tuple(self._expression.free_symbols), self._expression, ("numpy", "scipy")
         )
 
         self._parameters: dict[str, Union[pint.Quantity, xr.DataArray]] = {}

weldx/geometry.py

@@ -2,6 +2,7 @@
 from __future__ import annotations
 
 import copy
+import warnings
 from dataclasses import InitVar, dataclass
 from pathlib import Path
 from typing import TYPE_CHECKING, Union
@@ -211,7 +212,14 @@ def get_section_length(self, position: float) -> pint.Quantity:
 
         """
         if self._series.is_expression:
-            length = self._length_expr.evaluate(max_coord=position).data
+            # ignore unit stripped warning, as it is expected.
+            # Note, that the result still has the unit,
+            # it is stripped during computation (scipy.integrate)
+            with warnings.catch_warnings():
+                warnings.filterwarnings(
+                    "ignore", category=pint.errors.UnitStrippedWarning
+                )
+                length = self._length_expr.evaluate(max_coord=position).data
         else:
             length = self._len_section_disc(position=position)
         if length <= 0:

weldx/tests/test_core.py

@@ -199,6 +199,20 @@ def test_evaluate_exceptions(ma_def, variables, exception_type, test_name):
         with pytest.raises(exception_type):
             ma_def.evaluate(**variables)
 
+    @staticmethod
+    def test_integrate_length_computation():
+        """Ensure we can integrate with Sympy during length computation."""
+        from weldx import DynamicShapeSegment
+
+        class MySegment(DynamicShapeSegment):
+            def __init__(self):
+                f = "x * sin(s) + y * s"
+                p = dict(x=Q_([1, 0, 0], "mm"), y=Q_([0, 1, 0], "mm"))
+                super().__init__(f, parameters=p)
+
+        s = MySegment()
+        assert s.get_section_length(1).u == Q_("mm")
+
 
 # --------------------------------------------------------------------------------------
 # TimeSeries
@@ -468,7 +482,7 @@ def test_interp_time_warning():
     @pytest.mark.parametrize(
         "time,  exception_type, test_name",
         [
-            # (DTI(["2010-10-10"]), ValueError, "# wrong type #1"),
+            # (DTI(["2010-10-10"]), ValueError, "# wrong type #1"),  # skipcq: PY-W0069
             ("a string", TypeError, "# wrong type #2"),
             ([1, 2, 3], TypeError, "# wrong type #3"),
             (1, TypeError, "# wrong type #4"),