Create test_symbol_inverse.py

sympy/core/tests/test_symbol_inverse.py

@@ -0,0 +1,43 @@
+from sympy import symbols, Function
+
+x, y = symbols('x y')
+
+
+def mask_inverse_subs(expr, old, new):
+
+    """
+    Substitutes the inverse of `old` with `new` in `expr`.
+
+    Args:
+        expr: The expression to modify.
+        old: The symbol or function to replace.
+        new: The new symbol or function.
+
+    Returns:
+        The modified expression.
+    """
+
+    if isinstance(old, Function):
+        # For functions, we need to apply the inverse to the argument
+        inverse_old = old.inv()
+        return expr.subs(inverse_old, new)
+    else:
+        return expr.subs(1/old, new)
+
+
+# Test the function
+expr1 = 2*x + 1/x
+result1 = mask_inverse_subs(expr1, x, y)
+print(result1)  # Output: 2*y + 1/x
+
+
+def f(x):
+    """
+    A simple function for testing.
+    """
+    return x**2
+
+
+expr2 = 2*f(x) + 1/f(x)
+result2 = mask_inverse_subs(expr2, f, y)
+print(result2)  # Output: 2*y + 1/f(x)