Re: [Qemu-block] [PATCH v2] iotests: handle TypeError for Python3 in test 242

[Eduardo Habkost]

On Fri, Feb 22, 2019 at 02:26:13PM +0300, Andrey Shinkevich wrote:
> The data type for bytes in Python3 differs from the one in Python2.
> Those cases should be managed separately.
> 
> v1:
> In the first version, the TypeError in Python3 was handled as the
> exception.
> Discussed in the e-mail thread with the Message ID:
> <address@hidden>
> 
> Signed-off-by: Andrey Shinkevich <address@hidden>
> Reported-by: Kevin Wolf <address@hidden>
> ---
>  tests/qemu-iotests/242 | 8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/tests/qemu-iotests/242 b/tests/qemu-iotests/242
> index 16c65ed..446fbf8 100755
> --- a/tests/qemu-iotests/242
> +++ b/tests/qemu-iotests/242
> @@ -20,6 +20,7 @@
>  
>  import iotests
>  import json
> +import sys
>  from iotests import qemu_img_create, qemu_io, qemu_img_pipe, \
>      file_path, img_info_log, log, filter_qemu_io
>  
> @@ -65,9 +66,12 @@ def toggle_flag(offset):
>      with open(disk, "r+b") as f:
>          f.seek(offset, 0)
>          c = f.read(1)
> -        toggled = chr(ord(c) ^ bitmap_flag_unknown)
> +        toggled = ord(c) ^ bitmap_flag_unknown
>          f.seek(-1, 1)
> -        f.write(toggled)
> +        if sys.version_info.major >= 3:
> +            f.write(bytes([toggled]))
> +        else:
> +            f.write(chr(toggled))

Pretending we are dealing with text strings and using str/ord is
a python2-specific quirk.  I think it would be nice to get rid of
it.

Python 2 has bytearray(), which behaves more similarly to the
bytes type from Python 3.  If we use it, we can make the code
more python3-like:

diff --git a/tests/qemu-iotests/242 b/tests/qemu-iotests/242
index 16c65edcd7..7794fd4a70 100755
--- a/tests/qemu-iotests/242
+++ b/tests/qemu-iotests/242
@@ -64,10 +64,12 @@ def write_to_disk(offset, size):
 def toggle_flag(offset):
     with open(disk, "r+b") as f:
         f.seek(offset, 0)
-        c = f.read(1)
-        toggled = chr(ord(c) ^ bitmap_flag_unknown)
+        # The casts to bytearray() below are only necessary
+        # for Python 2 compatibility
+        c = bytearray(f.read(1))[0]
+        toggled = c ^ bitmap_flag_unknown
         f.seek(-1, 1)
-        f.write(toggled)
+        f.write(bytearray([toggled]))
 
 
 qemu_img_create('-f', iotests.imgfmt, disk, '1M')

-- 
Eduardo