Styling multi-line conditions in 'if' statements?


Question

Sometimes I break long conditions in ifs 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?

1
596
5/30/2017 5:35:39 PM

Accepted Answer

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.

654
5/27/2016 1:32:28 PM

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.


Licensed under: CC-BY-SA with attribution
Not affiliated with: Stack Overflow
Icon