Issue #14099: Writing to ZipFile and reading multiple ZipExtFiles is

threadsafe now.

Lib/zipfile.py

@@ -13,6 +13,7 @@ import stat
 import shutil
 import struct
 import binascii
+import threading
 
 
 try:
@@ -647,12 +648,14 @@ def _get_decompressor(compress_type):
 
 
 class _SharedFile:
-    def __init__(self, file, pos, close):
+    def __init__(self, file, pos, close, lock):
         self._file = file
         self._pos = pos
         self._close = close
+        self._lock = lock
 
     def read(self, n=-1):
+        with self._lock:
             self._file.seek(self._pos)
             data = self._file.read(n)
             self._pos = self._file.tell()
@@ -990,6 +993,7 @@ class ZipFile:
             self.fp = file
             self.filename = getattr(file, 'name', None)
         self._fileRefCnt = 1
+        self._lock = threading.RLock()
 
         try:
             if mode == 'r':
@@ -1214,7 +1218,7 @@ class ZipFile:
             zinfo = self.getinfo(name)
 
         self._fileRefCnt += 1
-        zef_file = _SharedFile(self.fp, zinfo.header_offset, self._fpclose)
+        zef_file = _SharedFile(self.fp, zinfo.header_offset, self._fpclose, self._lock)
         try:
             # Skip the file header:
             fheader = zef_file.read(sizeFileHeader)
@@ -1410,6 +1414,7 @@ class ZipFile:
 
         zinfo.file_size = st.st_size
         zinfo.flag_bits = 0x00
+        with self._lock:
             self.fp.seek(self.start_dir, 0)
             zinfo.header_offset = self.fp.tell()    # Start of header bytes
             if zinfo.compress_type == ZIP_LZMA:
@@ -1498,6 +1503,7 @@ class ZipFile:
                 "Attempt to write to ZIP archive that was already closed")
 
         zinfo.file_size = len(data)            # Uncompressed size
+        with self._lock:
             self.fp.seek(self.start_dir, 0)
             zinfo.header_offset = self.fp.tell()    # Start of header data
             if compress_type is not None:
@@ -1543,6 +1549,15 @@ class ZipFile:
 
         try:
             if self.mode in ("w", "a") and self._didModify: # write ending records
+                with self._lock:
+                    self.fp.seek(self.start_dir, 0)
+                    self._write_end_record()
+        finally:
+            fp = self.fp
+            self.fp = None
+            self._fpclose(fp)
+
+    def _write_end_record(self):
         self.fp.seek(self.start_dir, 0)
         for zinfo in self.filelist:         # write central directory
             dt = zinfo.date_time
@@ -1643,10 +1658,6 @@ class ZipFile:
         self.fp.write(endrec)
         self.fp.write(self._comment)
         self.fp.flush()
-        finally:
-            fp = self.fp
-            self.fp = None
-            self._fpclose(fp)
 
     def _fpclose(self, fp):
         assert self._fileRefCnt > 0

Misc/NEWS

@@ -218,6 +218,9 @@ Core and Builtins
 Library
 -------
 
+- Issue #14099: Writing to ZipFile and reading multiple ZipExtFiles is
+  threadsafe now.
+
 - Issue #19361: JSON decoder now raises JSONDecodeError instead of ValueError.
 
 - Issue #18518: timeit now rejects statements which can't be compiled outside