Overwrite environment deepcopy

formulae/environment.py

@@ -2,6 +2,7 @@
 # For more info see: https://github.com/pydata/patsy/blob/master/patsy/eval.py
 import inspect
 import numbers
+import dill
 
 
 class VarLookupDict:
@@ -75,6 +76,9 @@ def capture(cls, env=0, reference=0):
         finally:
             del frame
 
+    def __deepcopy__(self, memo):
+        return dill.copy(self)
+
     def _namespace_ids(self):
         return [id(n) for n in self._namespaces]
 

formulae/tests/test_environment.py

@@ -1,5 +1,6 @@
 import pytest
 from formulae.environment import VarLookupDict, Environment
+from copy import deepcopy
 
 
 def test_varlookup_get():
@@ -85,3 +86,10 @@ def test_evalenv_equality():
 
     env_outer = Environment.capture(1)
     assert env != env_outer
+
+
+def test_evalenv_deepcopy():
+    a = 1
+    env = Environment.capture()
+    clone_env = deepcopy(env)
+    assert clone_env.namespace["a"] == a

requirements.txt

@@ -1,3 +1,4 @@
 numpy>=1.16
 pandas>=1.0.0
 scipy>=1.5.4
+dill>=0.3.4

setup.py

@@ -24,7 +24,7 @@ def get_requirements():
 
 def get_version():
     with open(VERSION_FILE, encoding="utf-8") as buff:
-        exec(buff.read()) # pylint: disable=exec-used
+        exec(buff.read())  # pylint: disable=exec-used
     return vars()["__version__"]