Discussion on: 3 Common Mistakes that Python Newbies Make

[Vlastimil Pospichal]

This is a bit faster, because the first condition is met most often:

if year % 4 != 0:
    return False
if year % 100 != 0:
    return True
if year % 400 != 0:
    return False
return True

Shorter version:

if year % 4 != 0:
    return False
if year % 100 != 0:
    return True
return year % 400 == 0

Shortest version:

return year % 4 == 0 and (year % 100 != 0 or year % 400 == 0)

[Ryan Palo]

That’s a good point! I feel like that order would be more intuitive for students as well! It does have the slight downside of using “negative comparisons” but I think the ease of understanding definitely outweighs that. 😁

[Vlastimil Pospichal]

Negative comparisons are needed to eliminate else from source codes.

[Ryan Palo]

I’m not 100% sure that else is a bad thing. But I agree that using negative comparisons isn’t a terrible thing. Maybe more of a “all things being equal, try to use positive rather than negative if possible” kind of thing.

[Vlastimil Pospichal]

Eliminating else made my source code cleaner and faster. I use else in ternary operator only. I transformed structure if-else into ternary expression in many times.

Some languages (XSLT for example) are without "else". This inspired me.