How do I break an if test condition onto multiple lines?

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Let's say I have a really long condition in python like

Python

if (ch >= 32 and ch <=64) or (ch >= 75 and ch <= 100) or ch = 106:
    ...

Let's say I wanted to break that condition onto multiple lines along the outer ors. How would I go about that? What is the proper indent level, or is it even possible?

I ask because I can't necessarily restructure this code. It's generated using a tool and that tool necessarily spits out really long test conditions sometimes. It's necessary. So I either have to do this using really long lines, or I need a way to break it up.

What I have tried:

I haven't tried anything yet, as I haven't installed Python yet. It's just a basic question about whitespace.

Posted 4-Nov-21 14:14pm

honey the codewitch

Updated 4-Nov-21 22:36pm

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Dave Kreskowiak · Accepted Answer · 2021-11-04T17:16:00

Solution 1

I'm no Python expert, but I think this could work:

Python

if (ch >= 32 and ch <=64) or \
   (ch >= 75 and ch <= 100) or \
   ch = 106:
    do_something()

There's also this Python Style Guide[^] to consult.

Posted 4-Nov-21 17:16pm

Dave Kreskowiak

Comments

honey the codewitch 5-Nov-21 1:29am

Are you sure it's not indented at the next level? My google fu isn't helpful right now, and I don't want to stop what I'm doing to start an install of that mess. Oh well. I'll figure it out one way or another. Thanks.

phil.o 5-Nov-21 2:57am

Apparently, whenever you write if (, this opens a virtual space where indentation is relaxed. The link provided by Dave shows several options you have to get a proper syntax, no scrolling required, just a link right to a code block with examples.
You do not have to use backslashes for multiline conditions, as we would do with C preprocessor directives, for example.

honey the codewitch 5-Nov-21 3:08am

Thanks, I totally blew by the link in the reply. It's the hour that it is. I'm not altogether with it right now. =)

phil.o 5-Nov-21 4:51am

Who would be? :p

phil.o 5-Nov-21 3:04am

Apparently, backslashes are not needed :)

honey the codewitch 5-Nov-21 4:34am

Not in that case, but there are other cases where it's needed. It makes code generation a bear. Fortunately in my current case the blast radius of this problem is limited to if () statements.

Richard MacCutchan · Accepted Answer · 2021-11-04T22:36:00

Solution 2

I use a double indent so they are seen as still part of the if statement. Also put the expressions in parentheses:

Python

if (squares[row][0] != 0
        and squares[row][1] == squares[row][0]
        and squares[row][2] == squares[row][0]):
    draw_line(row, 0, row, 2, colour)
    return

Posted 4-Nov-21 22:36pm

Richard MacCutchan

Comments

honey the codewitch 5-Nov-21 5:02am

That was my original plan for Python. I just wasn't sure if it was valid. Actually right now I think my multiline conditionals are indented once rather than twice but it's an easy fix in my generation template. the big issue is knowing what's valid, and secondarily what's pretty. I'm on the fence about double indenting multiline conditionals hanging off of ifs. It's prettier to corner case it, but I don't like it because it's not consistent with the general rule of indenting I follow through the rest of my code. It just rubs me wrong.