Comparison Style

[llanitedave]

Given that 

s = some static value
i = a value incremented during a loop

I'm used to comparing them as

if i == s:
    # some code

But for some unknown reason I did a switch

if s == i:
    # same code

It didn't seem to make any difference at first glance, so I just got to wondering --

Is there a standard for comparison order?  Is there any kind of performance difference?  Is there even a tradition for one or the other?  Are there any gotchas?

Do I need to get a hobby?