Re: if, continuation and indentation

[Jean-Michel Pichavant]

Pete Forman wrote:

HH  writes:

 > I have a question about best practices when it comes to line
 > wrapping/ continuation and indentation, specifically in the case of
 > an if statement.

There are several good suggestions for formatting but no-one has
mentioned rewriting the code.  Use a boolean variable to hold the
result of the condition and then the if statement is more readable.
  

It has been suggested. ;)

JM
--
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Re: if, continuation and indentation

[Pete Forman]

HH  writes:

 > I have a question about best practices when it comes to line
 > wrapping/ continuation and indentation, specifically in the case of
 > an if statement.

There are several good suggestions for formatting but no-one has
mentioned rewriting the code.  Use a boolean variable to hold the
result of the condition and then the if statement is more readable.
-- 
Pete Forman-./\.-
West Sussex, UK  -./\.-
http://petef.22web.net -./\.-
petef4+use...@gmail.com  -./\.-
-- 
http://mail.python.org/mailman/listinfo/python-list

Re: if, continuation and indentation

[Greg Couch]

On May 27, 5:22 am, HH  wrote:
> I have a question about best practices when it comes to line wrapping/
> continuation and indentation, specifically in the case of an if
> statement.
>
> When I write an if statement with many conditions, I prefer to use a
> parenthesis around the whole block and get the implicit continuation,
> rather than ending each line with an escape character.  Thus, using
> the example from the style guide (http://www.python.org/dev/peps/
> pep-0008/) I would write:
>
>     if (width == 0 and
>         height == 0 and
>         color == 'red' and
>         emphasis == 'strong' or
>         highlight > 100):
>         raise ValueError("sorry, you lose")
>
> The problem should be obvious -- it's not easy to see where the
> conditional ends and the statement begins since they have the same
> indentation.  Part of the problem, I suppose, is that Emacs indents
> 'height' and the other lines in the conditional to 4 spaces (because
> of the parenthesis).  How do people deal with this situation?
>
> Thanks,
> Henrik

To show another alternative, I like:

 if (width == 0
 and height == 0
 and color == 'red'
 and emphasis == 'strong'
 or highlight > 100):
 raise ValueError("sorry, you lose")

This works because and/or can not start an expression, so it is
obvious
that they continue the expression from the previous line.  If I run
out
of room to put a full and/or clause on one line, then I'll indent the
subclause two levels.

-- Greg
-- 
http://mail.python.org/mailman/listinfo/python-list

Re: if, continuation and indentation

[Aahz]

In article ,
Tim Chase   wrote:
>
>While it's not PEP material, I tend to use the coding standards I 
>learned working for Computer Sciences Corporation (10 yrs ago, so 
>things may have changed) that mandated 2 levels of indentation 
>for continued lines, turning the above into
>
>   if (width == 0 and
>   height == 0 and
>   color == 'red' and
>   emphasis == 'strong' or
>   highlight>  100):
>   # or the closing "):" on this line,
>   # aligned with the previous line
>   raise ValueError("sorry, you lose")

+1
-- 
Aahz (a...@pythoncraft.com)   <*> http://www.pythoncraft.com/

"If you don't know what your program is supposed to do, you'd better not
start writing it."  --Dijkstra
-- 
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Re: if, continuation and indentation

[Giacomo Boffi]

HH  writes:

>   if (width == 0 and
>   height == 0 and
>   color == 'red' and
>   emphasis == 'strong' or
>   highlight > 100):
>   raise ValueError("sorry, you lose")

 
if (width == 0 and
height == 0 and
color == 'red' and
emphasis == 'strong' or
highlight > 100):

raise ValueError("sorry, you lose")

-- 
compro mobili vecchi - vendo mobili antichi
-- 
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Re: if, continuation and indentation

[Colin J. Williams]

On 31-May-10 17:15 PM, Lie Ryan wrote:

On 05/31/10 05:10, Colin J. Williams wrote:

On 30-May-10 01:50 AM, Nathan Rice wrote:

 On 27-May-10 08:48 AM, Xavier Ho wrote:
  >   On 27 May 2010 22:22, HHmailto:henri...@gmail.com>>  >>   wrote:

  >
  >if (width == 0 and
  >height == 0 and
  >color == 'red' and
  >emphasis == 'strong' or
  >highlight>   100):
  >raise ValueError("sorry, you lose")
  >
  >
  >   I've gotta say - I've bumped into this problem before,
 and I'm sure many
  >   other have - this is a valid question. It just hasn't
 bothered me enough
  >   to ask...
  >
  >   Correct me if I'm wrong, but I think the following is
 equivalent, and
  >   looks better. Although this won't fix all ugly cases in
 that problem..
  >
  >   if (width, height, color, emphasis) == (0, 0, 'red',
 'strong') or
  >   highlight>   100:
  > raise ValueError("sorry, you lose")
  >
  >   Cheers,
  >   Xav

 but nobody commented.

 Colin W.


 Colin:
 Sure, you can do it that way.  IMO, though, the OP was  wrong,
 and so
 is the PEP.  Source code is meant to communicate.  So it must
 transmit
 the correct information to the computer; it also must inform your
 coworkers.  That means that you have a responsibility to care
what
 they think, though you privately have your opinions.  Another
reason
 the PEP is faulty in this circumstance is that a misplaced
 backslash,
 or a missing one, is easily found and fixed.  A misplaced
 parentheses,
 or just one of a pair, will transform your source code into
 something
 which may compile and then give faulty results:  a disaster.
 So keep it simple, and make it legible.
 Yours,
 John


 IMHO complete garbage, if your editor doesn't show misplaced or
 missing parenthesis by highlighting you're using the wrong editor :)




Perhaps the arrangement below shows the matching a little better than
the Xav suggestion.  The main point is that, to me, the tuple shows the
item by item matching better than a series of and clauses:

# tif.py

(width, height, color, emphasis)= 0, 0, 'red', 'strong'
highlight= 99
if (width, height, color, emphasis) ==  \
(0, 0,  'red', 'strong') or highlight>   100:
raise ValueError("sorry, you lose")


How about:

all(a == b for a,b in ((width, 0), (height, 0), (color, 'red'),
(emphasis, 'strong'


You need to add "or highlight > 100"



--
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Re: if, continuation and indentation

[Lie Ryan]

On 05/31/10 05:10, Colin J. Williams wrote:
> On 30-May-10 01:50 AM, Nathan Rice wrote:
>> On 27-May-10 08:48 AM, Xavier Ho wrote:
>>  >  On 27 May 2010 22:22, HH> > > >>  wrote:
>>
>>  >
>>  >   if (width == 0 and
>>  >   height == 0 and
>>  >   color == 'red' and
>>  >   emphasis == 'strong' or
>>  >   highlight>  100):
>>  >   raise ValueError("sorry, you lose")
>>  >
>>  >
>>  >  I've gotta say - I've bumped into this problem before,
>> and I'm sure many
>>  >  other have - this is a valid question. It just hasn't
>> bothered me enough
>>  >  to ask...
>>  >
>>  >  Correct me if I'm wrong, but I think the following is
>> equivalent, and
>>  >  looks better. Although this won't fix all ugly cases in
>> that problem..
>>  >
>>  >  if (width, height, color, emphasis) == (0, 0, 'red',
>> 'strong') or
>>  >  highlight>  100:
>>  >raise ValueError("sorry, you lose")
>>  >
>>  >  Cheers,
>>  >  Xav
>>
>> but nobody commented.
>>
>> Colin W.
>>
>>
>> Colin:
>> Sure, you can do it that way.  IMO, though, the OP was  wrong,
>> and so
>> is the PEP.  Source code is meant to communicate.  So it must
>> transmit
>> the correct information to the computer; it also must inform your
>> coworkers.  That means that you have a responsibility to care
>> what
>> they think, though you privately have your opinions.  Another
>> reason
>> the PEP is faulty in this circumstance is that a misplaced
>> backslash,
>> or a missing one, is easily found and fixed.  A misplaced
>> parentheses,
>> or just one of a pair, will transform your source code into
>> something
>> which may compile and then give faulty results:  a disaster.
>> So keep it simple, and make it legible.
>> Yours,
>> John
>>
>>
>> IMHO complete garbage, if your editor doesn't show misplaced or
>> missing parenthesis by highlighting you're using the wrong editor :)
>>
>>
> 
> Perhaps the arrangement below shows the matching a little better than
> the Xav suggestion.  The main point is that, to me, the tuple shows the
> item by item matching better than a series of and clauses:
> 
> # tif.py
> 
> (width, height, color, emphasis)= 0, 0, 'red', 'strong'
> highlight= 99
> if (width, height, color, emphasis) ==  \
>(0, 0,  'red', 'strong') or highlight>  100:
>raise ValueError("sorry, you lose")

How about:

all(a == b for a,b in ((width, 0), (height, 0), (color, 'red'),
(emphasis, 'strong'
-- 
http://mail.python.org/mailman/listinfo/python-list

Re: if, continuation and indentation

[Colin J. Williams]

On 30-May-10 01:50 AM, Nathan Rice wrote:

I prefer to just break such things into multiple lines.  You're doing
that already anyhow, it's not much of a speed hit, and it makes exactly
what you're testing explicit.  If I break a statement onto multiple
lines I only use parenthesis, and that is as a last resort.  In my
opinion there's almost always some combination of variable assignments
and lambda expressions that uses fewer lines and is clearer.

is_correct_style = width == 0 and height == 0 and color == 'red'
if (is_correct_style and emphasis == 'strong') or highlight > 100:


On Sat, May 29, 2010 at 8:59 PM, Mark Lawrence mailto:breamore...@yahoo.co.uk>> wrote:

On 30/05/2010 01:23, john wrote:

On May 28, 10:37 am, "Colin J. Williams"mailto:cjwilliam...@gmail.com>>
wrote:

On 28-May-10 05:54 AM, Jonathan Hartley wrote:

On May 27, 1:57 pm, Jean-Michel
Pichavantmailto:jeanmic...@sequans.com>>
wrote:

HH wrote:

I have a question about best practices when it
comes to line wrapping/
continuation and indentation, specifically in
the case of an if
statement.


When I write an if statement with many
conditions, I prefer to use a
parenthesis around the whole block and get the
implicit continuation,
rather than ending each line with an escape
character.  Thus, using
the example from the style guide
(http://www.python.org/dev/peps/
pep-0008/) I would write:


  if (width == 0 and
  height == 0 and
  color == 'red' and
  emphasis == 'strong' or
  highlight>100):
  raise ValueError("sorry, you lose")


The problem should be obvious -- it's not easy
to see where the
conditional ends and the statement begins since
they have the same
indentation.  Part of the problem, I suppose, is
that Emacs indents
'height' and the other lines in the conditional
to 4 spaces (because
of the parenthesis).  How do people deal with
this situation?


Thanks,
Henrik


One possible solution


  if (
  width == 0 and
  height == 0 and
  color == 'red' and
  emphasis == 'strong' or
  highlight>100
 ):
  raise ValueError("sorry, you lose")


JM


I've always liked this, or even:


if (
width == 0 and
height == 0 and
color == 'red' and
emphasis == 'strong' or
highlight>100
):
raise ValueError("sorry, you lose")


but my co-workers have uniformly gone bananas whenever I
try it.


I liked:

On 27-May-10 08:48 AM, Xavier Ho wrote:
 >  On 27 May 2010 22:22, HHmailto:henri...@gmail.com>> >>  wrote:

 >
 >   if (width == 0 and
 >   height == 0 and
 >   color == 'red' and
 >   emphasis == 'strong' or
 >   highlight>  100):
 >   raise ValueError("sorry, you lose")
 >
 >
 >  I've gotta say - I've bumped into this problem before,
and I'm sure many
 >  other have - this is a valid question. It just hasn't
bothered me enough
 >  to ask...
 >
 >  Correct me if I'm wrong, but I think the following is
equivalent, and
 >  looks better. Although this won't fix all ugly cases in
that problem..
 >
 >  if (width, height, color, emphasis) == (0, 0, 'red',
'strong') or
 >  highlight>  100:
 >raise ValueError("sorry, you lose")
 >
 >  Cheers,
 >  Xav

  

Re: if, continuation and indentation

[Nathan Rice]

I prefer to just break such things into multiple lines.  You're doing that
already anyhow, it's not much of a speed hit, and it makes exactly what
you're testing explicit.  If I break a statement onto multiple lines I only
use parenthesis, and that is as a last resort.  In my opinion there's almost
always some combination of variable assignments and lambda expressions that
uses fewer lines and is clearer.

is_correct_style = width == 0 and height == 0 and color == 'red'
if (is_correct_style and emphasis == 'strong') or highlight > 100:


On Sat, May 29, 2010 at 8:59 PM, Mark Lawrence wrote:

> On 30/05/2010 01:23, john wrote:
>
>> On May 28, 10:37 am, "Colin J. Williams"
>> wrote:
>>
>>> On 28-May-10 05:54 AM, Jonathan Hartley wrote:
>>>
>>>  On May 27, 1:57 pm, Jean-Michel Pichavant
 wrote:

> HH wrote:
>
>> I have a question about best practices when it comes to line wrapping/
>> continuation and indentation, specifically in the case of an if
>> statement.
>>
>
>>>  When I write an if statement with many conditions, I prefer to use a
>> parenthesis around the whole block and get the implicit continuation,
>> rather than ending each line with an escape character.  Thus, using
>> the example from the style guide (http://www.python.org/dev/peps/
>> pep-0008/) I would write:
>>
>
>>>   if (width == 0 and
>>  height == 0 and
>>  color == 'red' and
>>  emphasis == 'strong' or
>>  highlight>100):
>>  raise ValueError("sorry, you lose")
>>
>
>>>  The problem should be obvious -- it's not easy to see where the
>> conditional ends and the statement begins since they have the same
>> indentation.  Part of the problem, I suppose, is that Emacs indents
>> 'height' and the other lines in the conditional to 4 spaces (because
>> of the parenthesis).  How do people deal with this situation?
>>
>
>>>  Thanks,
>> Henrik
>>
>
>>>  One possible solution
>

>>>   if (
>  width == 0 and
>  height == 0 and
>  color == 'red' and
>  emphasis == 'strong' or
>  highlight>100
> ):
>  raise ValueError("sorry, you lose")
>

>>>  JM
>

>>>  I've always liked this, or even:

>>>
>>> if (
width == 0 and
height == 0 and
color == 'red' and
emphasis == 'strong' or
highlight>100
):
raise ValueError("sorry, you lose")

>>>
>>>  but my co-workers have uniformly gone bananas whenever I try it.

>>>
>>> I liked:
>>>
>>> On 27-May-10 08:48 AM, Xavier Ho wrote:
>>>  >  On 27 May 2010 22:22, HH  >> henri...@gmail.com>>  wrote:
>>>
>>>  >
>>>  >   if (width == 0 and
>>>  >   height == 0 and
>>>  >   color == 'red' and
>>>  >   emphasis == 'strong' or
>>>  >   highlight>  100):
>>>  >   raise ValueError("sorry, you lose")
>>>  >
>>>  >
>>>  >  I've gotta say - I've bumped into this problem before, and I'm sure
>>> many
>>>  >  other have - this is a valid question. It just hasn't bothered me
>>> enough
>>>  >  to ask...
>>>  >
>>>  >  Correct me if I'm wrong, but I think the following is equivalent, and
>>>  >  looks better. Although this won't fix all ugly cases in that
>>> problem..
>>>  >
>>>  >  if (width, height, color, emphasis) == (0, 0, 'red', 'strong') or
>>>  >  highlight>  100:
>>>  >raise ValueError("sorry, you lose")
>>>  >
>>>  >  Cheers,
>>>  >  Xav
>>>
>>> but nobody commented.
>>>
>>> Colin W.
>>>
>>
>> Colin:
>> Sure, you can do it that way.  IMO, though, the OP was  wrong, and so
>> is the PEP.  Source code is meant to communicate.  So it must transmit
>> the correct information to the computer; it also must inform your
>> coworkers.  That means that you have a responsibility to care what
>> they think, though you privately have your opinions.  Another reason
>> the PEP is faulty in this circumstance is that a misplaced backslash,
>> or a missing one, is easily found and fixed.  A misplaced parentheses,
>> or just one of a pair, will transform your source code into something
>> which may compile and then give faulty results:  a disaster.
>> So keep it simple, and make it legible.
>> Yours,
>> John
>>
>
> IMHO complete garbage, if your editor doesn't show misplaced or missing
> parenthesis by highlighting you're using the wrong editor :)
>
> Regards.
>
> Mark Lawrence.
>
>
>
> --
> http://mail.python.org/mailman/listinfo/python-list
>
-- 
http://mail.python.org/mailman/listinfo/python-list

Re: if, continuation and indentation

[Mark Lawrence]

On 30/05/2010 01:23, john wrote:

On May 28, 10:37 am, "Colin J. Williams"
wrote:

On 28-May-10 05:54 AM, Jonathan Hartley wrote:


On May 27, 1:57 pm, Jean-Michel Pichavant
wrote:

HH wrote:

I have a question about best practices when it comes to line wrapping/
continuation and indentation, specifically in the case of an if
statement.



When I write an if statement with many conditions, I prefer to use a
parenthesis around the whole block and get the implicit continuation,
rather than ending each line with an escape character.  Thus, using
the example from the style guide (http://www.python.org/dev/peps/
pep-0008/) I would write:



  if (width == 0 and
  height == 0 and
  color == 'red' and
  emphasis == 'strong' or
  highlight>100):
  raise ValueError("sorry, you lose")



The problem should be obvious -- it's not easy to see where the
conditional ends and the statement begins since they have the same
indentation.  Part of the problem, I suppose, is that Emacs indents
'height' and the other lines in the conditional to 4 spaces (because
of the parenthesis).  How do people deal with this situation?



Thanks,
Henrik



One possible solution



  if (
  width == 0 and
  height == 0 and
  color == 'red' and
  emphasis == 'strong' or
  highlight>100
 ):
  raise ValueError("sorry, you lose")



JM



I've always liked this, or even:



if (
width == 0 and
height == 0 and
color == 'red' and
emphasis == 'strong' or
highlight>100
):
raise ValueError("sorry, you lose")



but my co-workers have uniformly gone bananas whenever I try it.


I liked:

On 27-May-10 08:48 AM, Xavier Ho wrote:
  >  On 27 May 2010 22:22, HH  > 
 wrote:

  >
  >   if (width == 0 and
  >   height == 0 and
  >   color == 'red' and
  >   emphasis == 'strong' or
  >   highlight>  100):
  >   raise ValueError("sorry, you lose")
  >
  >
  >  I've gotta say - I've bumped into this problem before, and I'm sure many
  >  other have - this is a valid question. It just hasn't bothered me enough
  >  to ask...
  >
  >  Correct me if I'm wrong, but I think the following is equivalent, and
  >  looks better. Although this won't fix all ugly cases in that problem..
  >
  >  if (width, height, color, emphasis) == (0, 0, 'red', 'strong') or
  >  highlight>  100:
  >raise ValueError("sorry, you lose")
  >
  >  Cheers,
  >  Xav

but nobody commented.

Colin W.


Colin:
Sure, you can do it that way.  IMO, though, the OP was  wrong, and so
is the PEP.  Source code is meant to communicate.  So it must transmit
the correct information to the computer; it also must inform your
coworkers.  That means that you have a responsibility to care what
they think, though you privately have your opinions.  Another reason
the PEP is faulty in this circumstance is that a misplaced backslash,
or a missing one, is easily found and fixed.  A misplaced parentheses,
or just one of a pair, will transform your source code into something
which may compile and then give faulty results:  a disaster.
So keep it simple, and make it legible.
Yours,
John


IMHO complete garbage, if your editor doesn't show misplaced or missing 
parenthesis by highlighting you're using the wrong editor :)


Regards.

Mark Lawrence.


--
http://mail.python.org/mailman/listinfo/python-list

Re: if, continuation and indentation

[john]

On May 28, 10:37 am, "Colin J. Williams" 
wrote:
> On 28-May-10 05:54 AM, Jonathan Hartley wrote:
>
> > On May 27, 1:57 pm, Jean-Michel Pichavant
> > wrote:
> >> HH wrote:
> >>> I have a question about best practices when it comes to line wrapping/
> >>> continuation and indentation, specifically in the case of an if
> >>> statement.
>
> >>> When I write an if statement with many conditions, I prefer to use a
> >>> parenthesis around the whole block and get the implicit continuation,
> >>> rather than ending each line with an escape character.  Thus, using
> >>> the example from the style guide (http://www.python.org/dev/peps/
> >>> pep-0008/) I would write:
>
> >>>      if (width == 0 and
> >>>          height == 0 and
> >>>          color == 'red' and
> >>>          emphasis == 'strong' or
> >>>          highlight>  100):
> >>>          raise ValueError("sorry, you lose")
>
> >>> The problem should be obvious -- it's not easy to see where the
> >>> conditional ends and the statement begins since they have the same
> >>> indentation.  Part of the problem, I suppose, is that Emacs indents
> >>> 'height' and the other lines in the conditional to 4 spaces (because
> >>> of the parenthesis).  How do people deal with this situation?
>
> >>> Thanks,
> >>> Henrik
>
> >> One possible solution
>
> >>      if (
> >>              width == 0 and
> >>              height == 0 and
> >>              color == 'red' and
> >>              emphasis == 'strong' or
> >>              highlight>  100
> >>         ):
> >>          raise ValueError("sorry, you lose")
>
> >> JM
>
> > I've always liked this, or even:
>
> >    if (
> >        width == 0 and
> >        height == 0 and
> >        color == 'red' and
> >        emphasis == 'strong' or
> >        highlight>  100
> >    ):
> >        raise ValueError("sorry, you lose")
>
> > but my co-workers have uniformly gone bananas whenever I try it.
>
> I liked:
>
> On 27-May-10 08:48 AM, Xavier Ho wrote:
>  > On 27 May 2010 22:22, HH  
> > wrote:
>
>  >
>  >         if (width == 0 and
>  >             height == 0 and
>  >             color == 'red' and
>  >             emphasis == 'strong' or
>  >             highlight > 100):
>  >             raise ValueError("sorry, you lose")
>  >
>  >
>  > I've gotta say - I've bumped into this problem before, and I'm sure many
>  > other have - this is a valid question. It just hasn't bothered me enough
>  > to ask...
>  >
>  > Correct me if I'm wrong, but I think the following is equivalent, and
>  > looks better. Although this won't fix all ugly cases in that problem..
>  >
>  > if (width, height, color, emphasis) == (0, 0, 'red', 'strong') or
>  > highlight > 100:
>  >      raise ValueError("sorry, you lose")
>  >
>  > Cheers,
>  > Xav
>
> but nobody commented.
>
> Colin W.

Colin:
Sure, you can do it that way.  IMO, though, the OP was  wrong, and so
is the PEP.  Source code is meant to communicate.  So it must transmit
the correct information to the computer; it also must inform your
coworkers.  That means that you have a responsibility to care what
they think, though you privately have your opinions.  Another reason
the PEP is faulty in this circumstance is that a misplaced backslash,
or a missing one, is easily found and fixed.  A misplaced parentheses,
or just one of a pair, will transform your source code into something
which may compile and then give faulty results:  a disaster.
So keep it simple, and make it legible.
Yours,
John
-- 
http://mail.python.org/mailman/listinfo/python-list

Re: if, continuation and indentation

[Colin J. Williams]

On 28-May-10 05:54 AM, Jonathan Hartley wrote:

On May 27, 1:57 pm, Jean-Michel Pichavant
wrote:

HH wrote:

I have a question about best practices when it comes to line wrapping/
continuation and indentation, specifically in the case of an if
statement.



When I write an if statement with many conditions, I prefer to use a
parenthesis around the whole block and get the implicit continuation,
rather than ending each line with an escape character.  Thus, using
the example from the style guide (http://www.python.org/dev/peps/
pep-0008/) I would write:



 if (width == 0 and
 height == 0 and
 color == 'red' and
 emphasis == 'strong' or
 highlight>  100):
 raise ValueError("sorry, you lose")



The problem should be obvious -- it's not easy to see where the
conditional ends and the statement begins since they have the same
indentation.  Part of the problem, I suppose, is that Emacs indents
'height' and the other lines in the conditional to 4 spaces (because
of the parenthesis).  How do people deal with this situation?



Thanks,
Henrik


One possible solution

 if (
 width == 0 and
 height == 0 and
 color == 'red' and
 emphasis == 'strong' or
 highlight>  100
):
 raise ValueError("sorry, you lose")

JM


I've always liked this, or even:

   if (
   width == 0 and
   height == 0 and
   color == 'red' and
   emphasis == 'strong' or
   highlight>  100
   ):
   raise ValueError("sorry, you lose")


but my co-workers have uniformly gone bananas whenever I try it.

I liked:

On 27-May-10 08:48 AM, Xavier Ho wrote:
> On 27 May 2010 22:22, HH  > wrote:
>
> if (width == 0 and
> height == 0 and
> color == 'red' and
> emphasis == 'strong' or
> highlight > 100):
> raise ValueError("sorry, you lose")
>
>
> I've gotta say - I've bumped into this problem before, and I'm sure many
> other have - this is a valid question. It just hasn't bothered me enough
> to ask...
>
> Correct me if I'm wrong, but I think the following is equivalent, and
> looks better. Although this won't fix all ugly cases in that problem..
>
> if (width, height, color, emphasis) == (0, 0, 'red', 'strong') or
> highlight > 100:
>  raise ValueError("sorry, you lose")
>
> Cheers,
> Xav

but nobody commented.

Colin W.

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Re: if, continuation and indentation

[Jonathan Hartley]

On 28/05/2010 11:34, Jean-Michel Pichavant wrote:

Jonathan Hartley wrote:

On May 27, 1:57 pm, Jean-Michel Pichavant 
wrote:

HH wrote:

I have a question about best practices when it comes to line wrapping/
continuation and indentation, specifically in the case of an if
statement.
  When I write an if statement with many conditions, I prefer 
to use a

parenthesis around the whole block and get the implicit continuation,
rather than ending each line with an escape character.  Thus, using
the example from the style guide (http://www.python.org/dev/peps/
pep-0008/) I would write:
  if (width == 0 and
height == 0 and
color == 'red' and
emphasis == 'strong' or
highlight > 100):
raise ValueError("sorry, you lose")
  The problem should be obvious -- it's not easy to see where the
conditional ends and the statement begins since they have the same
indentation.  Part of the problem, I suppose, is that Emacs indents
'height' and the other lines in the conditional to 4 spaces (because
of the parenthesis).  How do people deal with this situation?
  Thanks,
Henrik

One possible solution

if (
width == 0 and
height == 0 and
color == 'red' and
emphasis == 'strong' or
highlight > 100
   ):
raise ValueError("sorry, you lose")

JM 


I've always liked this, or even:

  if (
  width == 0 and
  height == 0 and
  color == 'red' and
  emphasis == 'strong' or
  highlight > 100
  ):
  raise ValueError("sorry, you lose")


but my co-workers have uniformly gone bananas whenever I try it.
I tried to give a layout that fits the OP way of doing, but I would 
not use what I described above, so I can understand why your co 
workers go bananas :)


when it comes to extended conditions in if statement I prefer to write 
something like


if self.haveLost():
   raise ValueError("sorry, you lose")

It drastically improves the reading


Good point.

+1 for naming the condition, hooray for self-documenting code.

Sometime last year at my workplace, we started referring to comments as 
'lies', we now always try to use techniques like this instead of comments.


--
Jonathan Hartley  Made of meat.  http://tartley.com
tart...@tartley.com   +44 7737 062 225   twitter/skype: tartley

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Re: if, continuation and indentation

[Jean-Michel Pichavant]

Jonathan Hartley wrote:

On May 27, 1:57 pm, Jean-Michel Pichavant 
wrote:
  

HH wrote:


I have a question about best practices when it comes to line wrapping/
continuation and indentation, specifically in the case of an if
statement.
  
When I write an if statement with many conditions, I prefer to use a

parenthesis around the whole block and get the implicit continuation,
rather than ending each line with an escape character.  Thus, using
the example from the style guide (http://www.python.org/dev/peps/
pep-0008/) I would write:
  
if (width == 0 and

height == 0 and
color == 'red' and
emphasis == 'strong' or
highlight > 100):
raise ValueError("sorry, you lose")
  
The problem should be obvious -- it's not easy to see where the

conditional ends and the statement begins since they have the same
indentation.  Part of the problem, I suppose, is that Emacs indents
'height' and the other lines in the conditional to 4 spaces (because
of the parenthesis).  How do people deal with this situation?
  
Thanks,

Henrik
  

One possible solution

if (
width == 0 and
height == 0 and
color == 'red' and
emphasis == 'strong' or
highlight > 100
   ):
raise ValueError("sorry, you lose")

JM  



I've always liked this, or even:

  if (
  width == 0 and
  height == 0 and
  color == 'red' and
  emphasis == 'strong' or
  highlight > 100
  ):
  raise ValueError("sorry, you lose")


but my co-workers have uniformly gone bananas whenever I try it.
  
I tried to give a layout that fits the OP way of doing, but I would not 
use what I described above, so I can understand why your co workers go 
bananas :)


when it comes to extended conditions in if statement I prefer to write 
something like


if self.haveLost():
   raise ValueError("sorry, you lose")

It drastically improves the reading because it splits the notion of what 
to do in which case, and how do you identify the cases (i.e. what should 
I do when I've lost, and how do I know that I've lost). If you don't 
want to pollute your upper namespace you can embed the function that way:


def foo():
   width = 0
   height = 0
   color = 'red'
   emphasis = 'strong'

   def haveLost():
   return not width and not height and color == 'red' and emphasis 
=='strong'


   if haveLost():
   raise ValueError("sorry you lose")

It has the cool side effect to name your condition as well, that helps 
debugging the condition *a lot*.


JM
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Re: if, continuation and indentation

[Jonathan Hartley]

On May 27, 1:57 pm, Jean-Michel Pichavant 
wrote:
> HH wrote:
> > I have a question about best practices when it comes to line wrapping/
> > continuation and indentation, specifically in the case of an if
> > statement.
>
> > When I write an if statement with many conditions, I prefer to use a
> > parenthesis around the whole block and get the implicit continuation,
> > rather than ending each line with an escape character.  Thus, using
> > the example from the style guide (http://www.python.org/dev/peps/
> > pep-0008/) I would write:
>
> >     if (width == 0 and
> >         height == 0 and
> >         color == 'red' and
> >         emphasis == 'strong' or
> >         highlight > 100):
> >         raise ValueError("sorry, you lose")
>
> > The problem should be obvious -- it's not easy to see where the
> > conditional ends and the statement begins since they have the same
> > indentation.  Part of the problem, I suppose, is that Emacs indents
> > 'height' and the other lines in the conditional to 4 spaces (because
> > of the parenthesis).  How do people deal with this situation?
>
> > Thanks,
> > Henrik
>
> One possible solution
>
>     if (
>             width == 0 and
>             height == 0 and
>             color == 'red' and
>             emphasis == 'strong' or
>             highlight > 100
>        ):
>         raise ValueError("sorry, you lose")
>
> JM  

I've always liked this, or even:

  if (
  width == 0 and
  height == 0 and
  color == 'red' and
  emphasis == 'strong' or
  highlight > 100
  ):
  raise ValueError("sorry, you lose")


but my co-workers have uniformly gone bananas whenever I try it.
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Re: if, continuation and indentation

[HH]

On May 27, 11:37 am, Alain Ketterlin 
wrote:
> HH  writes:
> >     if (width == 0 and
> >         height == 0 and
> >         color == 'red' and
> >         emphasis == 'strong' or
> >         highlight > 100):
> >         raise ValueError("sorry, you lose")
>
> I prefer to see the "and" at the beginning of continuation lines, and
> usually group related items. I never mix operators without putting
> explicit parentheses. Something like:
>
>      if  (  width == 0 and height == 0
>             and color == 'red'
>             and ( emphasis == 'strong' or highlight > 100 ) ):
>          raise ValueError("sorry, you lose")

Thanks for all suggestions!  I like this solution a lot.

I agree with your statement about mixed operators and explicit
parentheses -- expecially since the eye/brain parser often does it
wrong, and I believe you demonstrated that above...

In [29]: print(False and (False or True))
False
In [30]: print(False and False or True)
True

> If you use a backslashes at the end of line, emacs will double-indent
> the following lines, but I think you said you prefer paretheses...

Yes, I much prefer the parentheses -- partly because PEP-8 suggests it
but mostly because the escapes get lost too easily.


HH
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Re: if, continuation and indentation

[Jean-Michel Pichavant]

MRAB wrote:

HH wrote:

I have a question about best practices when it comes to line wrapping/
continuation and indentation, specifically in the case of an if
statement.

When I write an if statement with many conditions, I prefer to use a
parenthesis around the whole block and get the implicit continuation,
rather than ending each line with an escape character.  Thus, using
the example from the style guide (http://www.python.org/dev/peps/
pep-0008/) I would write:

if (width == 0 and
height == 0 and
color == 'red' and
emphasis == 'strong' or
highlight > 100):
raise ValueError("sorry, you lose")

The problem should be obvious -- it's not easy to see where the
conditional ends and the statement begins since they have the same
indentation.  Part of the problem, I suppose, is that Emacs indents
'height' and the other lines in the conditional to 4 spaces (because
of the parenthesis).  How do people deal with this situation?


I would probably use half-indentation:

if (width == 0 and
  height == 0 and
  color == 'red' and
  emphasis == 'strong' or
  highlight > 100):
raise ValueError("sorry, you lose")

Try doing that with tabs! :-)


   if (width ==0 and
' \\  // ' and height == 0 and
'  \\//  ' and color == 'red' and
'   /OO\ ' and emphasis == 'strong' and
'   \> 100):
   raise ValueError("sorry, you lose")

Try doing this with spaces !! :p

JM
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Re: if, continuation and indentation

[Alain Ketterlin]

HH  writes:

> if (width == 0 and
> height == 0 and
> color == 'red' and
> emphasis == 'strong' or
> highlight > 100):
> raise ValueError("sorry, you lose")

I prefer to see the "and" at the beginning of continuation lines, and
usually group related items. I never mix operators without putting
explicit parentheses. Something like:

 if  (  width == 0 and height == 0
and color == 'red'
and ( emphasis == 'strong' or highlight > 100 ) ):
 raise ValueError("sorry, you lose")

Anyway, choose your style and stick to it.

> The problem should be obvious -- it's not easy to see where the
> conditional ends and the statement begins since they have the same
> indentation.  Part of the problem, I suppose, is that Emacs indents
> 'height' and the other lines in the conditional to 4 spaces (because
> of the parenthesis).

Emacs aligns "height" with "width", not with the parenthesis. You can
put as many spaces as you want before "(" or between "(" and "width",
and the following lines will follow. At least that's what happens with
my stock emacs-snapshot on ubuntu, with python.el.

If you use a backslashes at the end of line, emacs will double-indent
the following lines, but I think you said you prefer paretheses...

-- Alain.
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Re: if, continuation and indentation

[Harald Luessen]

On Thu, 27 May 2010 HH wrote:

>I have a question about best practices when it comes to line wrapping/
>continuation and indentation, specifically in the case of an if
>statement.
>
>if (width == 0 and
>height == 0 and
>color == 'red' and
>emphasis == 'strong' or
>highlight > 100):
>raise ValueError("sorry, you lose")

My solution would probably look like this:

if (   width == 0
   and height == 0
   and color == 'red'
   and emphasis == 'strong'
or highlight > 100
   ):
raise ValueError("sorry, you lose")

Harald

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Re: if, continuation and indentation

[MRAB]

HH wrote:

I have a question about best practices when it comes to line wrapping/
continuation and indentation, specifically in the case of an if
statement.

When I write an if statement with many conditions, I prefer to use a
parenthesis around the whole block and get the implicit continuation,
rather than ending each line with an escape character.  Thus, using
the example from the style guide (http://www.python.org/dev/peps/
pep-0008/) I would write:

if (width == 0 and
height == 0 and
color == 'red' and
emphasis == 'strong' or
highlight > 100):
raise ValueError("sorry, you lose")

The problem should be obvious -- it's not easy to see where the
conditional ends and the statement begins since they have the same
indentation.  Part of the problem, I suppose, is that Emacs indents
'height' and the other lines in the conditional to 4 spaces (because
of the parenthesis).  How do people deal with this situation?


I would probably use half-indentation:

if (width == 0 and
  height == 0 and
  color == 'red' and
  emphasis == 'strong' or
  highlight > 100):
raise ValueError("sorry, you lose")

Try doing that with tabs! :-)
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Re: if, continuation and indentation

[Tim Chase]

On 05/27/2010 07:22 AM, HH wrote:

When I write an if statement with many conditions, I prefer to use a
parenthesis around the whole block and get the implicit continuation,
rather than ending each line with an escape character.  Thus, using
the example from the style guide (http://www.python.org/dev/peps/
pep-0008/) I would write:

 if (width == 0 and
 height == 0 and
 color == 'red' and
 emphasis == 'strong' or
 highlight>  100):
 raise ValueError("sorry, you lose")


While it's not PEP material, I tend to use the coding standards I 
learned working for Computer Sciences Corporation (10 yrs ago, so 
things may have changed) that mandated 2 levels of indentation 
for continued lines, turning the above into


  if (width == 0 and
  height == 0 and
  color == 'red' and
  emphasis == 'strong' or
  highlight>  100):
  # or the closing "):" on this line,
  # aligned with the previous line
  raise ValueError("sorry, you lose")

which is fairly close to Jean-Michel's proposal.

-tkc



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Re: if, continuation and indentation

[Xavier Ho]

On 27 May 2010 23:26, Xavier Ho  wrote:

> Oh, one minor optimisation. You can put the last condition first
>

I take that back. You really can't, without using more parans or ifs.
Apologies.

-Xav
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Re: if, continuation and indentation

[Xavier Ho]

On 27 May 2010 22:57, Jean-Michel Pichavant  wrote:

>  One possible solution
>>
>>   if (
>>   width == 0 and
>>   height == 0 and
>>   color == 'red' and
>>   emphasis == 'strong' or
>>   highlight > 100
>>  ):
>>   raise ValueError("sorry, you lose")
>>
>
Oh, one minor optimisation. You can put the last condition first:

  if (
  highlight > 100 or
  width == 0 and
  height == 0 and
  color == 'red' and
  emphasis == 'strong'
 ):
  raise ValueError("sorry, you lose")
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Re: if, continuation and indentation

[Xavier Ho]

On 27 May 2010 22:57, Jean-Michel Pichavant  wrote:

> One possible solution
>
>   if (
>   width == 0 and
>   height == 0 and
>   color == 'red' and
>   emphasis == 'strong' or
>   highlight > 100
>  ):
>   raise ValueError("sorry, you lose")
>
> But... but you have a sad face in one line! :(

Good trick.

-Xav
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Re: if, continuation and indentation

[Jean-Michel Pichavant]

HH wrote:

I have a question about best practices when it comes to line wrapping/
continuation and indentation, specifically in the case of an if
statement.

When I write an if statement with many conditions, I prefer to use a
parenthesis around the whole block and get the implicit continuation,
rather than ending each line with an escape character.  Thus, using
the example from the style guide (http://www.python.org/dev/peps/
pep-0008/) I would write:

if (width == 0 and
height == 0 and
color == 'red' and
emphasis == 'strong' or
highlight > 100):
raise ValueError("sorry, you lose")

The problem should be obvious -- it's not easy to see where the
conditional ends and the statement begins since they have the same
indentation.  Part of the problem, I suppose, is that Emacs indents
'height' and the other lines in the conditional to 4 spaces (because
of the parenthesis).  How do people deal with this situation?

Thanks,
Henrik
  

One possible solution

   if (
   width == 0 and
   height == 0 and
   color == 'red' and
   emphasis == 'strong' or
   highlight > 100
  ):
   raise ValueError("sorry, you lose")


JM  
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Re: if, continuation and indentation

[Martin P. Hellwig]

On 05/27/10 13:22, HH wrote:

I have a question about best practices when it comes to line wrapping/
continuation and indentation, specifically in the case of an if
statement.

When I write an if statement with many conditions, I prefer to use a
parenthesis around the whole block and get the implicit continuation,
rather than ending each line with an escape character.  Thus, using
the example from the style guide (http://www.python.org/dev/peps/
pep-0008/) I would write:

 if (width == 0 and
 height == 0 and
 color == 'red' and
 emphasis == 'strong' or
 highlight>  100):
 raise ValueError("sorry, you lose")

The problem should be obvious -- it's not easy to see where the
conditional ends and the statement begins since they have the same
indentation.  Part of the problem, I suppose, is that Emacs indents
'height' and the other lines in the conditional to 4 spaces (because
of the parenthesis).  How do people deal with this situation?

Thanks,
Henrik


Well style guide aside (if pylint is happy with it, so am I) it depends 
on what I want to emphasize.


For example if it is really one long line with every item in it being 
equally important I do this:
if width == 0 and height == 0 and color == 'red' and emphasis == 
'strong' \
 or 
highlight > 100:

raise ValueError("sorry, you lose")

In case it doesn't display correctly, I break up the line to nearest 
80th character and align the remaining part on the next line to the 
right to the 80th character.


If I want to emphasize visually a certain part I would do something like 
this:


if width == 0 and height == 0 and color == 'red' \
   and emphasis == 'strong' or highlight > 100:
raise ValueError("sorry, you lose")

But these are my preference, and since it is most likely that I have to
read again what I have written I write it in a way that it is most 
readable to me within the constraints of pylint.


--
mph

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Re: if, continuation and indentation

[Xavier Ho]

On 27 May 2010 22:22, HH  wrote:

>if (width == 0 and
>height == 0 and
>color == 'red' and
>emphasis == 'strong' or
>highlight > 100):
>raise ValueError("sorry, you lose")
>

I've gotta say - I've bumped into this problem before, and I'm sure many
other have - this is a valid question. It just hasn't bothered me enough to
ask...

Correct me if I'm wrong, but I think the following is equivalent, and looks
better. Although this won't fix all ugly cases in that problem.

if (width, height, color, emphasis) == (0, 0, 'red', 'strong') or highlight
> 100:
raise ValueError("sorry, you lose")

Cheers,
Xav
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if, continuation and indentation

[HH]

I have a question about best practices when it comes to line wrapping/
continuation and indentation, specifically in the case of an if
statement.

When I write an if statement with many conditions, I prefer to use a
parenthesis around the whole block and get the implicit continuation,
rather than ending each line with an escape character.  Thus, using
the example from the style guide (http://www.python.org/dev/peps/
pep-0008/) I would write:

if (width == 0 and
height == 0 and
color == 'red' and
emphasis == 'strong' or
highlight > 100):
raise ValueError("sorry, you lose")

The problem should be obvious -- it's not easy to see where the
conditional ends and the statement begins since they have the same
indentation.  Part of the problem, I suppose, is that Emacs indents
'height' and the other lines in the conditional to 4 spaces (because
of the parenthesis).  How do people deal with this situation?

Thanks,
Henrik
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