Barry Drake wrote:
> On 30/03/12 16:19, Evert Rol wrote:
>> Not sure. In the sense that you can "optimise" (refactor) it in the same
>> way you could do with C. Eg: results = [0, 0, 0]
>> flags = [0, 1, 2, 3]
>> for flag in flags:
>> results = getflag(flag, results)
>>
>
> That's exactly what I hoped for. I hadn't realised I can initialise a
> list in one go - it seems that lists work a lot like the arrays I was
> used to in c. Thanks to the others who took the time to answer. Just
> now, Asokan's solution is a bit obscure to me - I'll work on that one,
> but the above is lovely and elegant; and easy to understand. Someone
> asked about the getflag function - it is:
>
> def getflag(thisflag, results):
> if (thisflag == 2):
> results[0] += 1
> elif (thisflag == 1):
> results[1] += 1
> elif (thisflag == 0):
> results[2] += 1
> return(results)
>
> In c, I would have used switch and case, but I gather there is no direct
> equivalent in Python ... But it works as is.
Here is an alternative to if...elif..., a table (python list) that
translates from the flag to an index into the results table.
flag_to_result = [2, 1, 0]
def update_results(flag, results):
try:
results[flag_to_result[flag]] += 1
except IndexError:
pass # ignore flags other than 0, 1, 2
results = [0, 0, 0]
flags = [0, 1, 2, 3, 4, 3, 2, 1]
for flag in flags:
update_results(flag, results)
print results
The following operates on an even higher level:
from collections import Counter
flags = [0, 1, 2, 3, 4, 3, 2, 1]
counter = Counter(flags)
results = [counter[2], counter[1], counter[0]]
print results
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