[GitHub] [arrow] pitrou commented on a change in pull request #8312: ARROW-9941: [Python] Better string representation for extension types

[GitBox <gi...@apache.org>]

pitrou commented on a change in pull request #8312:
URL: https://github.com/apache/arrow/pull/8312#discussion_r499604700



##########
File path: python/pyarrow/types.pxi
##########
@@ -697,6 +697,9 @@ cdef class ExtensionType(BaseExtensionType):
         else:
             return NotImplemented
 
+    def __str__(self):

Review comment:
       I think this can be removed now (after which the `str` test will need to be fixed).

##########
File path: cpp/src/arrow/python/extension_type.cc
##########
@@ -71,6 +72,14 @@ PyObject* DeserializeExtInstance(PyObject* type_class,
 
 static const char* kExtensionName = "arrow.py_extension_type";
 
+std::string PyExtensionType::ToString() const {
+  std::stringstream ss;
+  OwnedRef instance(GetInstance());
+  ss << "extension<" << this->extension_name() << "<" << Py_TYPE(instance.obj())->tp_name
+     << ">>";
+  return ss.str();
+}

Review comment:
       This works fine, but there is one thing missing. Since `ToString` is called from arbitrary C++ code, the GIL needs to be taken. This is achieved by adding:
   ```c++
   PyAcquireGIL lock;
   ```
   at the beginning of this method definition.
   




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