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* [PATCH] trace: avoid "is" with a literal Python 3.8 warnings
@ 2019-10-10 12:21 Stefan Hajnoczi
  2019-10-10 12:36 ` Daniel P. Berrangé
                   ` (3 more replies)
  0 siblings, 4 replies; 5+ messages in thread
From: Stefan Hajnoczi @ 2019-10-10 12:21 UTC (permalink / raw)
  To: qemu-devel; +Cc: Daniel P . Berrangé, Stefan Hajnoczi

The following statement produces a SyntaxWarning with Python 3.8:

  if len(format) is 0:
  scripts/tracetool/__init__.py:459: SyntaxWarning: "is" with a literal. Did you mean "=="?

Use the conventional len(x) == 0 syntax instead.

Reported-by: Daniel P. Berrangé <berrange@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
 scripts/tracetool/__init__.py | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/scripts/tracetool/__init__.py b/scripts/tracetool/__init__.py
index 04279fa62e..44c118bc2a 100644
--- a/scripts/tracetool/__init__.py
+++ b/scripts/tracetool/__init__.py
@@ -456,12 +456,12 @@ def generate(events, group, format, backends,
     import tracetool
 
     format = str(format)
-    if len(format) is 0:
+    if len(format) == 0:
         raise TracetoolError("format not set")
     if not tracetool.format.exists(format):
         raise TracetoolError("unknown format: %s" % format)
 
-    if len(backends) is 0:
+    if len(backends) == 0:
         raise TracetoolError("no backends specified")
     for backend in backends:
         if not tracetool.backend.exists(backend):
-- 
2.21.0



^ permalink raw reply	[flat|nested] 5+ messages in thread

* Re: [PATCH] trace: avoid "is" with a literal Python 3.8 warnings
  2019-10-10 12:21 [PATCH] trace: avoid "is" with a literal Python 3.8 warnings Stefan Hajnoczi
@ 2019-10-10 12:36 ` Daniel P. Berrangé
  2019-10-10 14:02 ` Philippe Mathieu-Daudé
                   ` (2 subsequent siblings)
  3 siblings, 0 replies; 5+ messages in thread
From: Daniel P. Berrangé @ 2019-10-10 12:36 UTC (permalink / raw)
  To: Stefan Hajnoczi; +Cc: qemu-devel

On Thu, Oct 10, 2019 at 01:21:54PM +0100, Stefan Hajnoczi wrote:
> The following statement produces a SyntaxWarning with Python 3.8:
> 
>   if len(format) is 0:
>   scripts/tracetool/__init__.py:459: SyntaxWarning: "is" with a literal. Did you mean "=="?
> 
> Use the conventional len(x) == 0 syntax instead.
> 
> Reported-by: Daniel P. Berrangé <berrange@redhat.com>
> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
> ---
>  scripts/tracetool/__init__.py | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)

Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>

Regards,
Daniel
-- 
|: https://berrange.com      -o-    https://www.flickr.com/photos/dberrange :|
|: https://libvirt.org         -o-            https://fstop138.berrange.com :|
|: https://entangle-photo.org    -o-    https://www.instagram.com/dberrange :|


^ permalink raw reply	[flat|nested] 5+ messages in thread

* Re: [PATCH] trace: avoid "is" with a literal Python 3.8 warnings
  2019-10-10 12:21 [PATCH] trace: avoid "is" with a literal Python 3.8 warnings Stefan Hajnoczi
  2019-10-10 12:36 ` Daniel P. Berrangé
@ 2019-10-10 14:02 ` Philippe Mathieu-Daudé
  2019-10-10 16:13 ` Stefan Hajnoczi
  2019-10-11  6:01 ` Markus Armbruster
  3 siblings, 0 replies; 5+ messages in thread
From: Philippe Mathieu-Daudé @ 2019-10-10 14:02 UTC (permalink / raw)
  To: Stefan Hajnoczi, qemu-devel; +Cc: Daniel P . Berrangé

On 10/10/19 2:21 PM, Stefan Hajnoczi wrote:
> The following statement produces a SyntaxWarning with Python 3.8:
> 
>    if len(format) is 0:
>    scripts/tracetool/__init__.py:459: SyntaxWarning: "is" with a literal. Did you mean "=="?
> 
> Use the conventional len(x) == 0 syntax instead.

Ah this is a new change from 3.8...
https://docs.python.org/3.9/whatsnew/3.8.html

 From https://bugs.python.org/issue34850

> Reported-by: Daniel P. Berrangé <berrange@redhat.com>
> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>

> ---
>   scripts/tracetool/__init__.py | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/scripts/tracetool/__init__.py b/scripts/tracetool/__init__.py
> index 04279fa62e..44c118bc2a 100644
> --- a/scripts/tracetool/__init__.py
> +++ b/scripts/tracetool/__init__.py
> @@ -456,12 +456,12 @@ def generate(events, group, format, backends,
>       import tracetool
>   
>       format = str(format)
> -    if len(format) is 0:
> +    if len(format) == 0:
>           raise TracetoolError("format not set")
>       if not tracetool.format.exists(format):
>           raise TracetoolError("unknown format: %s" % format)
>   
> -    if len(backends) is 0:
> +    if len(backends) == 0:
>           raise TracetoolError("no backends specified")
>       for backend in backends:
>           if not tracetool.backend.exists(backend):
> 


^ permalink raw reply	[flat|nested] 5+ messages in thread

* Re: [PATCH] trace: avoid "is" with a literal Python 3.8 warnings
  2019-10-10 12:21 [PATCH] trace: avoid "is" with a literal Python 3.8 warnings Stefan Hajnoczi
  2019-10-10 12:36 ` Daniel P. Berrangé
  2019-10-10 14:02 ` Philippe Mathieu-Daudé
@ 2019-10-10 16:13 ` Stefan Hajnoczi
  2019-10-11  6:01 ` Markus Armbruster
  3 siblings, 0 replies; 5+ messages in thread
From: Stefan Hajnoczi @ 2019-10-10 16:13 UTC (permalink / raw)
  To: qemu-devel; +Cc: Daniel P . Berrangé

[-- Attachment #1: Type: text/plain, Size: 634 bytes --]

On Thu, Oct 10, 2019 at 01:21:54PM +0100, Stefan Hajnoczi wrote:
> The following statement produces a SyntaxWarning with Python 3.8:
> 
>   if len(format) is 0:
>   scripts/tracetool/__init__.py:459: SyntaxWarning: "is" with a literal. Did you mean "=="?
> 
> Use the conventional len(x) == 0 syntax instead.
> 
> Reported-by: Daniel P. Berrangé <berrange@redhat.com>
> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
> ---
>  scripts/tracetool/__init__.py | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)

Thanks, applied to my tracing tree:
https://github.com/stefanha/qemu/commits/tracing

Stefan

[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 488 bytes --]

^ permalink raw reply	[flat|nested] 5+ messages in thread

* Re: [PATCH] trace: avoid "is" with a literal Python 3.8 warnings
  2019-10-10 12:21 [PATCH] trace: avoid "is" with a literal Python 3.8 warnings Stefan Hajnoczi
                   ` (2 preceding siblings ...)
  2019-10-10 16:13 ` Stefan Hajnoczi
@ 2019-10-11  6:01 ` Markus Armbruster
  3 siblings, 0 replies; 5+ messages in thread
From: Markus Armbruster @ 2019-10-11  6:01 UTC (permalink / raw)
  To: Stefan Hajnoczi; +Cc: Daniel P . Berrangé, qemu-devel

Stefan Hajnoczi <stefanha@redhat.com> writes:

> The following statement produces a SyntaxWarning with Python 3.8:
>
>   if len(format) is 0:
>   scripts/tracetool/__init__.py:459: SyntaxWarning: "is" with a literal. Did you mean "=="?
>
> Use the conventional len(x) == 0 syntax instead.
>
> Reported-by: Daniel P. Berrangé <berrange@redhat.com>
> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
> ---
>  scripts/tracetool/__init__.py | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/scripts/tracetool/__init__.py b/scripts/tracetool/__init__.py
> index 04279fa62e..44c118bc2a 100644
> --- a/scripts/tracetool/__init__.py
> +++ b/scripts/tracetool/__init__.py
> @@ -456,12 +456,12 @@ def generate(events, group, format, backends,
>      import tracetool
>  
>      format = str(format)
> -    if len(format) is 0:
> +    if len(format) == 0:
>          raise TracetoolError("format not set")
>      if not tracetool.format.exists(format):
>          raise TracetoolError("unknown format: %s" % format)
>  
> -    if len(backends) is 0:
> +    if len(backends) == 0:
>          raise TracetoolError("no backends specified")
>      for backend in backends:
>          if not tracetool.backend.exists(backend):

For what it's worth, PEP 8 advises

    For sequences, (strings, lists, tuples), use the fact that empty
    sequences are false.

    Yes: if not seq:
         if seq:

    No:  if len(seq):
         if not len(seq):


^ permalink raw reply	[flat|nested] 5+ messages in thread

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Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed)
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2019-10-10 12:21 [PATCH] trace: avoid "is" with a literal Python 3.8 warnings Stefan Hajnoczi
2019-10-10 12:36 ` Daniel P. Berrangé
2019-10-10 14:02 ` Philippe Mathieu-Daudé
2019-10-10 16:13 ` Stefan Hajnoczi
2019-10-11  6:01 ` Markus Armbruster

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