perf(core): make sympify faster for Basic subclasses.

oscarbenjamin · oscarbenjamin · commit f7cecfea016d · 2020-10-17T23:20:08.000+01:00
The behaviour of sympify was changed in sympy#20128 so that sympifying a Basic subclass would be an error when strict=True. That change made the codepath for calling e.g. _sympify(Basic) slower as more checks would be done before returning. This commit adds an early raise for the case of calling _sympify(a) where a is a Basic subclass.
diff --git a/sympy/core/sympify.py b/sympy/core/sympify.py
@@ -344,8 +344,13 @@ def sympify(a, locals=None, convert_xor=True, strict=False, rational=False,
     #
     # https://github.com/sympy/sympy/issues/20124
     is_sympy = getattr(a, '__sympy__', None)
-    if is_sympy is True or (is_sympy is not None and not strict):
+    if is_sympy is True:
         return a
+    elif is_sympy is not None:
+        if not strict:
+            return a
+        else:
+            raise SympifyError(a)
 
     if isinstance(a, CantSympify):
         raise SympifyError(a)
