From db9788a58ee94116264cdedc2e9560cff2f546ce Mon Sep 17 00:00:00 2001
From: kouyouqi123 <1696906464@qq.com>
Date: Sun, 31 May 2026 13:56:41 +0800
Subject: [PATCH 1/3] fix: implement __iter__ on VarLookupDict to prevent
 CPython crash

VarLookupDict is a dict-like object but does not implement __iter__,
__len__, or keys(). This causes a CPython crash (via a KeyError: 0)
when Python's C-level error display code tries to iterate over the
locals dict during traceback formatting.

Fixes pydata/patsy#259
---
 patsy/eval.py | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/patsy/eval.py b/patsy/eval.py
index 9d1fba02..f878d05a 100644
--- a/patsy/eval.py
+++ b/patsy/eval.py
@@ -72,6 +72,20 @@ def get(self, key, default=None):
         except KeyError:
             return default
 
+    def __iter__(self):
+        seen = set()
+        for d in self._dicts:
+            for key in d:
+                if key not in seen:
+                    seen.add(key)
+                    yield key
+
+    def __len__(self):
+        return len(list(iter(self)))
+
+    def keys(self):
+        return list(iter(self))
+
     def __repr__(self):
         return "%s(%r)" % (self.__class__.__name__, self._dicts)
 

From 611e50962d53e0ab67271f78c441366aef23db3f Mon Sep 17 00:00:00 2001
From: kouyouqi123 <1696906464@qq.com>
Date: Sun, 31 May 2026 14:38:01 +0800
Subject: [PATCH 2/3] fix: use np.asarray(result).dtype instead of result.dtype
 for DataFrame compat

When _eval_factor receives a pandas DataFrame as result and
tries to raise a PatsyError, it accesses result.dtype which
doesn't exist on DataFrames (only .dtypes). This causes a
confusing secondary AttributeError instead of the intended
error message.

Fixes #232
---
 patsy/build.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/patsy/build.py b/patsy/build.py
index cbe25248..fe5ba79a 100644
--- a/patsy/build.py
+++ b/patsy/build.py
@@ -80,7 +80,7 @@ def _eval_factor(factor_info, data, NA_action):
         if not safe_issubdtype(np.asarray(result).dtype, np.number):
             raise PatsyError(
                 "when evaluating numeric factor %s, "
-                "I got non-numeric data of type '%s'" % (factor.name(), result.dtype),
+                "I got non-numeric data of type '%s'" % (factor.name(), np.asarray(result).dtype),
                 factor,
             )
         return result, NA_action.is_numerical_NA(result)

From 128b51db431d303a270b44053f2718df045024d0 Mon Sep 17 00:00:00 2001
From: "pre-commit-ci[bot]"
 <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Date: Sun, 31 May 2026 06:38:55 +0000
Subject: [PATCH 3/3] [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci
---
 patsy/build.py | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/patsy/build.py b/patsy/build.py
index fe5ba79a..4749e179 100644
--- a/patsy/build.py
+++ b/patsy/build.py
@@ -80,7 +80,8 @@ def _eval_factor(factor_info, data, NA_action):
         if not safe_issubdtype(np.asarray(result).dtype, np.number):
             raise PatsyError(
                 "when evaluating numeric factor %s, "
-                "I got non-numeric data of type '%s'" % (factor.name(), np.asarray(result).dtype),
+                "I got non-numeric data of type '%s'"
+                % (factor.name(), np.asarray(result).dtype),
                 factor,
             )
         return result, NA_action.is_numerical_NA(result)