Check to see if the file exists first in append mode

avrokit/url/google.py

@@ -120,17 +120,12 @@ def open(self) -> IO[Any]:
         self._current_local = tmpfile
         self._current_local_stream = self._current_local
         # Download to file if r/rb mode, or if append mode (to preserve existing content on failure)
-        if "r" in self.mode or "a" in self.mode:
-            # N.b. always writes in binary mode
+        if "r" in self.mode or ("a" in self.mode and blob.exists()):
             blob.download_to_file(tmpfile)
             tmpfile.seek(0)
-            if "a" in self.mode:
-                tmpfile.seek(0, 2)  # Seek to end for append mode
-            if "b" not in self.mode:
-                # So if the user wants to read text, we need to decode it
-                self._current_local_stream = io.TextIOWrapper(tmpfile, encoding="utf-8")
-        elif ("w" in self.mode or "a" in self.mode) and "b" not in self.mode:
-            # Same thing when we're writing text
+        if "a" in self.mode:
+            tmpfile.seek(0, 2)
+        if "b" not in self.mode:
             self._current_local_stream = io.TextIOWrapper(tmpfile, encoding="utf-8")
         stream = cast(IO[Any], self._current_local_stream)
         return stream

avrokit/url/s3.py

@@ -95,17 +95,12 @@ def open(self) -> IO[Any]:
         self._current_local = tmpfile
         self._current_local_stream = self._current_local
         # Download to file if "r"/"rb" mode, or if append mode (to preserve existing content on failure)
-        if "r" in self.mode or "a" in self.mode:
-            # N.b. always writes in binary mode
+        if "r" in self.mode or ("a" in self.mode and self.exists()):
             client.download_fileobj(self.bucket, self.path, tmpfile)
             tmpfile.seek(0)
-            if "a" in self.mode:
-                tmpfile.seek(0, 2)  # Seek to end for append mode
-            if "b" not in self.mode:
-                # So if the user wants to read text, we need to decode it
-                self._current_local_stream = io.TextIOWrapper(tmpfile, encoding="utf-8")
-        elif ("w" in self.mode or "a" in self.mode) and "b" not in self.mode:
-            # Same thing when we're writing text
+        if "a" in self.mode:
+            tmpfile.seek(0, 2)
+        if "b" not in self.mode:
             self._current_local_stream = io.TextIOWrapper(tmpfile, encoding="utf-8")
         stream = cast(IO[Any], self._current_local_stream)
         return stream

pyproject.toml

@@ -4,7 +4,7 @@
 
 [tool.poetry]
 name = "avrokit"
-version = "0.0.3"
+version = "0.0.4"
 description = "Python utilities for working with Avro data files"
 authors = ["Greg Brandt <brandt.greg@gmail.com>"]
 license = "Apache-2.0"