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

 

[Martin P. Hellwig]

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.

 

[Jean-Michel Pichavant]

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

 

[Tim Chase]

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

 

[MRAB]

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!

 

[Harald Luessen]

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

 

[Alain Ketterlin]

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.

 

[Jean-Michel Pichavant]

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
' \></ ' or highlight > 100):
raise ValueError("sorry, you lose")

Try doing this with spaces !!

JM

 

[HH]

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

 

[Jonathan Hartley]

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.

 

[Jean-Michel Pichavant]

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

 

[Jonathan Hartley]

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.

 

[Colin J. Williams]

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 2010 22:22, HH <[email protected]
>
> 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.

 

[john]

I liked:

On 27-May-10 08:48 AM, Xavier Ho 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

 

[Mark Lawrence]

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.

 

[Colin J. Williams]

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 <[email protected]

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

On May 28, 10:37 am, "Colin J. Williams"<[email protected]
<mailto:[email protected]>>
wrote:

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

On May 27, 1:57 pm, Jean-Michel
Pichavant<[email protected]
<mailto:[email protected]>>
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:

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.

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")

Colin W.

 

[Colin J. Williams]

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 <[email protected]

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

On May 28, 10:37 am, "Colin J. Williams"<[email protected]
<mailto:[email protected]>>
wrote:

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

On May 27, 1:57 pm, Jean-Michel
Pichavant<[email protected]
<mailto:[email protected]>>
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:

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.

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")

Colin W.

 

[Lie Ryan]

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'))))

 

[Colin J. Williams]

How about:

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

You need to add "or highlight > 100"

 

[Giacomo Boffi]

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")