Stefan Hajnoczi <stefa...@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 <berra...@redhat.com>
> Signed-off-by: Stefan Hajnoczi <stefa...@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):
