Issue #28449: tarfile.open() with mode "r" or "r:" now tries to open a tar

file with compression before trying to open it without compression.  Otherwise
it had 50% chance failed with ignore_zeros=True.

1 files changed, 3 insertions, 1 deletions

diff --git a/Lib/tarfile.py b/Lib/tarfile.py
index 721f9d7f91..999a99b978 100755
--- a/Lib/tarfile.py
+++ b/Lib/tarfile.py
@@ -1549,7 +1549,9 @@ class TarFile(object):
 
         if mode in ("r", "r:*"):
             # Find out which *open() is appropriate for opening the file.
-            for comptype in cls.OPEN_METH:
+            def not_compressed(comptype):
+                return cls.OPEN_METH[comptype] == 'taropen'
+            for comptype in sorted(cls.OPEN_METH, key=not_compressed):
                 func = getattr(cls, cls.OPEN_METH[comptype])
                 if fileobj is not None:
                     saved_pos = fileobj.tell()