coding style - Line continuation for list comprehensions or generator expressions in python

Question

How are you supposed to break up a very long list comprehension?

[something_that_is_pretty_long for something_that_is_pretty_long in somethings_that_are_pretty_long]

I have also seen somewhere that people that dislike using '' to break up lines, but never understood why. What is the reason behind this?

Answer 1

[x
 for
 x
 in
 (1,2,3)
]

works fine, so you can pretty much do as you please. I'd personally prefer

 [something_that_is_pretty_long
  for something_that_is_pretty_long
  in somethings_that_are_pretty_long]

The reason why isn't appreciated very much is that it appears at the end of a line, where it either doesn't stand out or needs extra padding, which has to be fixed when line lengths change:

x = very_long_term                     
  + even_longer_term_than_the_previous 
  + a_third_term

In such cases, use parens:

x = (very_long_term
     + even_longer_term_than_the_previous
     + a_third_term)