其中哪一个更像python？

Question

I'm doing some exploring of various languages I hadn't used before, using a simple Perl script as a basis for what I want to accomplish. I have a couple of versions of something, and I'm curious which is the preferred method when using Python -- or if neither is, what is?

Version 1:

workflowname = []
paramname = []
value = []
for line in lines:
        wfn, pn, v = line.split(",")
        workflowname.append(wfn)
        paramname.append(pn)
        value.append(v)

Version 2:

workflowname = []
paramname = []
value = []
i = 0;
for line in lines:
        workflowname.append("")
        paramname.append("")
        value.append("")
        workflowname[i], paramname[i], value[i] = line.split(",")
        i = i + 1

Personally, I prefer the second, but, as I said, I'm curious what someone who really knows Python would prefer.

Answer 1

A Pythonic solution might a bit like @Bogdan's, but using zip and argument unpacking

workflowname, paramname, value = zip(*[line.split(',') for line in lines])

If you're determined to use a for construct, though, the 1st is better.

Answer 2

Of your two attepts the 2nd one doesn't make any sense to me. Maybe in other languages it would. So from your two proposed approaces the 1st one is better.

Still I think the pythonic way would be something like Matt Luongo suggested.

Answer 3

Bogdan's answer is best. In general, if you need a loop counter (which you don't in this case), you should use enumerate instead of incrementing a counter:

for index, value in enumerate(lines):
    # do something with the value and the index

Answer 4

Version 1 is definitely better than version 2 (why put something in a list if you're just going to replace it?) but depending on what you're planning to do later, neither one may be a good idea. Parallel lists are almost never more convenient than lists of objects or tuples, so I'd consider:

# list of (workflow,paramname,value) tuples
items = []
for line in lines:
    items.append( line.split(",") ) 

Or:

class WorkflowItem(object):
    def __init__(self,workflow,paramname,value):
        self.workflow = workflow
        self.paramname = paramname
        self.value = value

# list of objects
items = []
for line in lines:
    items.append( WorkflowItem(*line.split(",")) ) 

(Also, nitpick: 4-space tabs are preferable to 8-space.)