linux-kernel - Re: [PATCH] scripts: Add Python 3 support to tracing/draw

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Date:   Wed, 25 Jul 2018 11:01:21 -0400
From:   Jeremy Cline <jcline@...hat.com>
To:     Masahiro Yamada <yamada.masahiro@...ionext.com>
Cc:     Michal Marek <michal.lkml@...kovi.net>,
        Frederic Weisbecker <fweisbec@...il.com>,
        Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] scripts: Add Python 3 support to
 tracing/draw_functrace.py

On 07/25/2018 10:39 AM, Masahiro Yamada wrote:
> 2018-07-21 4:35 GMT+09:00 Jeremy Cline <jcline@...hat.com>:
>> Use the print function. This maintains Python 2 support and should have
>> no functional change.
>>
>> Signed-off-by: Jeremy Cline <jcline@...hat.com>
>> ---
>>  scripts/tracing/draw_functrace.py | 3 ++-
>>  1 file changed, 2 insertions(+), 1 deletion(-)
>>
>> diff --git a/scripts/tracing/draw_functrace.py b/scripts/tracing/draw_functrace.py
>> index db40fa04cd51..7d44e796d362 100755
>> --- a/scripts/tracing/draw_functrace.py
>> +++ b/scripts/tracing/draw_functrace.py
>> @@ -20,6 +20,7 @@ Usage:
>>         $ scripts/draw_functrace.py < raw_trace_func > draw_functrace
>>         Then you have your drawn trace in draw_functrace
>>  """
>> +from __future__ import print_function
> 
> What do you need this line for?
> 
> I have not tested this,
> but I guess print(CallTree.ROOT) will work for Python 2.

Although "print(CallTree.ROOT)" (as a statement) works in Python 2,
its behavior is different than print (as a function) in Python 3. In
this case, there's no additional arguments being provided so the
behavior will match, but if someone added an argument it would work
differently on Python 2 vs Python 3:

Python 2.7.15
>>> print("hello", "world")
('hello', 'world')

Python 3.6.6
>>> print("hello, "world")
  File "<stdin>", line 1
    print("hello, "world")
                       ^
SyntaxError: invalid syntax

Importing the print_function works on Python 2.6+[0] and changes print
to be a function in Python 2 so it'll behave the same in 2 and 3. Given
that this script doesn't appear to change much it's probably not going
to save anyone from making that mistake, though. Would you prefer a
patch without it?

[0] https://docs.python.org/3/library/__future__.html

Regards,
Jeremy

> 
> 
> 
>>
>>  import sys, re
>> @@ -123,7 +124,7 @@ def main():
>>                 tree = tree.getParent(caller)
>>                 tree = tree.calls(callee, calltime)
>>
>> -       print CallTree.ROOT
>> +       print(CallTree.ROOT)
>>
>>  if __name__ == "__main__":
>>         main()
>> --
>> 2.17.1
>>
> 
> 
>