Issue #4756: zipfile.is_zipfile() now supports file-like objects.

Patch by Gabriel Genellina.

1 files changed, 19 insertions, 7 deletions

diff --git a/Lib/zipfile.py b/Lib/zipfile.py
index bb8fc53..66fe078 100644
--- a/Lib/zipfile.py
+++ b/Lib/zipfile.py
@@ -128,18 +128,30 @@ _CD64_NUMBER_ENTRIES_TOTAL = 7
 _CD64_DIRECTORY_SIZE = 8
 _CD64_OFFSET_START_CENTDIR = 9
 
-def is_zipfile(filename):
-    """Quickly see if file is a ZIP file by checking the magic number."""
+def _check_zipfile(fp):
     try:
-        fpin = open(filename, "rb")
-        endrec = _EndRecData(fpin)
-        fpin.close()
-        if endrec:
-            return True                 # file has correct magic number
+        if _EndRecData(fp):
+            return True         # file has correct magic number
     except IOError:
         pass
     return False
 
+def is_zipfile(filename):
+    """Quickly see if a file is a ZIP file by checking the magic number.
+
+    The filename argument may be a file or file-like object too.
+    """
+    result = False
+    try:
+        if hasattr(filename, "read"):
+            result = _check_zipfile(fp=filename)
+        else:
+            with open(filename, "rb") as fp:
+                result = _check_zipfile(fp)
+    except IOError:
+        pass
+    return result
+
 def _EndRecData64(fpin, offset, endrec):
     """
     Read the ZIP64 end-of-archive records and use that to update endrec