Issue #29094: Offsets in a ZIP file created with extern file object and modes

serhiy-storchaka · serhiy-storchaka · commit e465a9af8e87 · 2017-01-01T19:05:29.000+02:00
"w" and "x" now are relative to the start of the file.
diff --git a/Lib/zipfile.py b/Lib/zipfile.py
@@ -1102,11 +1102,12 @@ def __init__(self, file, mode="r", compression=ZIP_STORED, allowZip64=True):
                 # set the modified flag so central directory gets written
                 # even if no files are added to the archive
                 self._didModify = True
+                self._start_disk = 0
                 try:
-                    self.start_dir = self._start_disk = self.fp.tell()
+                    self.start_dir = self.fp.tell()
                 except (AttributeError, OSError):
                     self.fp = _Tellable(self.fp)
-                    self.start_dir = self._start_disk = 0
+                    self.start_dir = 0
                     self._seekable = False
                 else:
                     # Some file-like objects can provide tell() but not seek()
diff --git a/Misc/NEWS b/Misc/NEWS
@@ -40,6 +40,9 @@ Core and Builtins
 Library
 -------
 
+- Issue #29094: Offsets in a ZIP file created with extern file object and modes
+  "w" and "x" now are relative to the start of the file.
+
 - Issue #29085: Allow random.Random.seed() to use high quality OS randomness
   rather than the pid and time.
 
