line conditions in 'if' statements?
Sometimes I break long conditions in if
s onto several lines. The most obvious way to do this is:
if (cond1 == 'val1' and cond2 == 'val2' and
cond3 == 'val3' and cond4 == 'val4'):
do_something
Isn't very very appealing visually, because the action blends with the conditions. However, it is the natural way using correct Python indentation of 4 spaces.
For the moment I'm using:
if ( cond1 == 'val1' and cond2 == 'val2' and
cond3 == 'val3' and cond4 == 'val4'):
do_something
But this isn't very pretty. :-)
Can you recommend an alternative way?
You don't need to use 4 spaces on your second conditional line. Maybe use:
if (cond1 == 'val1' and cond2 == 'val2' and
cond3 == 'val3' and cond4 == 'val4'):
do_something
Also, don't forget the whitespace is more flexible than you might think:
if (
cond1 == 'val1' and cond2 == 'val2' and
cond3 == 'val3' and cond4 == 'val4'
):
do_something
if (cond1 == 'val1' and cond2 == 'val2' and
cond3 == 'val3' and cond4 == 'val4'):
do_something
Both of those are fairly ugly though.
Maybe lose the brackets (the Style Guide discourages this though)?
if cond1 == 'val1' and cond2 == 'val2' and
cond3 == 'val3' and cond4 == 'val4':
do_something
This at least gives you some differentiation.
Or even:
if cond1 == 'val1' and cond2 == 'val2' and
cond3 == 'val3' and
cond4 == 'val4':
do_something
I think I prefer:
if cond1 == 'val1' and
cond2 == 'val2' and
cond3 == 'val3' and
cond4 == 'val4':
do_something
Here's the Style Guide, which (since 2010) recommends using brackets.
I've resorted to the following in the degenerate case where it's simply AND's or OR's.
if all( [cond1 == 'val1', cond2 == 'val2', cond3 == 'val3', cond4 == 'val4'] ):
if any( [cond1 == 'val1', cond2 == 'val2', cond3 == 'val3', cond4 == 'val4'] ):
It shaves a few characters and makes it clear that there's no subtlety to the condition.
Someone has to champion use of vertical whitespace here! :)
if ( cond1 == val1
and cond2 == val2
and cond3 == val3
):
do_stuff()
This makes each condition clearly visible. It also allows cleaner expression of more complex conditions:
if ( cond1 == val1
or
( cond2_1 == val2_1
and cond2_2 >= val2_2
and cond2_3 != bad2_3
)
):
do_more_stuff()
Yes, we're trading off a bit of vertical real estate for clarity. Well worth it IMO.
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