[Python-Dev] if-syntax for regular for-loops

Andreas Nilsson adde at trialcode.com
Fri Oct 3 12:10:59 CEST 2008

First post so here it goes.
My name is Adde, and I'm a Swedish software developer. I've been  
programming for about 23 years now since starting with Basic on the  
C64. I've been through most well known and a couple of lesser known  
languages in search of the perfect one. At the moment I'm writing a  
custom ctypes interface to the Firebird database (need access to  
advanced features, portability to Windows and I definitely don't enjoy  
setting up GCC on Windows).
I've programmed a lot of C/C++ in my days so I thought I'd at least  
join the list and see if anything piques my interest enough to dive in.

With that out of the way, on to todays subject:
I use list comprehensions and generator expressions a lot and lately  
I've found myself writing a lot of code like this:

for i in items if i.some_field == some_value: i.do_something()

Naturally it won't work but it seems like a pretty straight-forward  
extension to allow compressing simple loops to fit on one line. The  
alternative, in my eyes, suggests there's something more happening  
than a simple include-test which makes it harder to comprehend.

for i in items:
	if i.some_field == some_value: i.do_something()

One possibility of course is to use a generator-expression but that  
makes it look like there are two for loops and it feels like a waste  
setting up a generator just for filtering.

for i in (i for i in items if some_field == some_value):

Stupid idea? Am I missing some obviously better way of achieving the  
same result?


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