bpo-43787: Add __iter__ to GzipFile, BZ2File, and LZMAFile (GH-25353)

Lib/bz2.py

@@ -197,6 +197,10 @@ class BZ2File(_compression.BaseStream):
         self._check_can_read()
         return self._buffer.readline(size)
 
+    def __iter__(self):
+        self._check_can_read()
+        return self._buffer.__iter__()
+
     def readlines(self, size=-1):
         """Read a list of lines of uncompressed bytes from the file.
 

Lib/gzip.py

@@ -398,6 +398,10 @@ class GzipFile(_compression.BaseStream):
         self._check_not_closed()
         return self._buffer.readline(size)
 
+    def __iter__(self):
+        self._check_not_closed()
+        return self._buffer.__iter__()
+
 
 class _GzipReader(_compression.DecompressReader):
     def __init__(self, fp):

Lib/lzma.py

@@ -221,6 +221,10 @@ class LZMAFile(_compression.BaseStream):
         self._check_can_read()
         return self._buffer.readline(size)
 
+    def __iter__(self):
+        self._check_can_read()
+        return self._buffer.__iter__()
+
     def write(self, data):
         """Write a bytes object to the file.
 

Misc/NEWS.d/next/Library/2021-04-12-15-15-50.bpo-43787.wCy_Wd.rst

@@ -0,0 +1,3 @@
+Add ``__iter__()`` method to :class:`bz2.BZ2File`, :class:`gzip.GzipFile`, and
+:class:`lzma.LZMAFile`. It makes iterating them about 2x faster. Patch by
+Inada Naoki.