From dade3f365a129cf2180cdf184fce819fc1badfbb Mon Sep 17 00:00:00 2001
From: "Colin B. Macdonald" <cbm@m.fsf.org>
Date: Sat, 1 Apr 2023 15:13:24 -0700
Subject: [PATCH] Use sys.modules hacks to prevent setting dps/prec

Fixes Issue #657.

Co-authored-by: Warren Weckesser <warren.weckesser@gmail.com>
---
 mpmath/__init__.py | 31 +++++++++++++++++++++++++++++++
 1 file changed, 31 insertions(+)

diff --git a/mpmath/__init__.py b/mpmath/__init__.py
index 683233bd1..d3e78e9ee 100644
--- a/mpmath/__init__.py
+++ b/mpmath/__init__.py
@@ -1,5 +1,8 @@
 __version__ = '1.3.0'
 
+import sys
+import types
+
 from .usertools import monitor, timing
 
 from .ctx_fp import FPContext
@@ -433,6 +436,34 @@
 unit_triangle = mp.unit_triangle
 sigmoid = mp.sigmoid
 
+
+class SetMPMathPrecisionError(RuntimeError):
+
+    def __init__(self, attribute):
+        self._attribute = attribute
+
+    def __str__(self):
+        name = self._attribute
+        return (f"cannot set '{name}' on 'mpmath'. Did you mean to "
+                f"set '{name}' on 'mpmath.mp'?")
+
+
+class _MPMathModuleType(types.ModuleType):
+
+    def _set_dps(self, value):
+        raise SetMPMathPrecisionError('dps')
+
+    dps = property(fset=_set_dps)
+
+    def _set_prec(self, value):
+        raise SetMPMathPrecisionError('prec')
+
+    prec = property(fset=_set_prec)
+
+
+sys.modules[__name__].__class__ = _MPMathModuleType
+
+
 # be careful when changing this name, don't use test*!
 def runtests():
     """