On 2011-11-25 13:40, lina wrote:
On Fri, Nov 25, 2011 at 7:19 PM, Steven D'Aprano<st...@pearwood.info> wrote:
f = open("some file")
dehydrons = {}
occurrence = {}
pairs = {}
for line in f.readlines():
parts = line.split()
# convert to ints
parts = [int(s) for s in parts]
pair = frozenset(parts[:2]) # order doesn't matter
if pair in dehydrons:
occurrence[pair] += 1
else:
dehydrons[pair] = parts[2]
occurrence[pair] = 1
pairs[pair] = pairs.get(pair, 0) + parts[2]
f.close()
for line in f.readlines():
parts = line.split()
#pair=set((parts[0],parts[1]))
#convert to ints
parts = [int(s) for s in parts]
pair = frozenset(parts[:2])
print(pair)
if pair in dehydrons:
occurence[pair] += 1
else:
dehydrons[pair] = parts[2]
pairs[pair] = pairs.get(pair,0) + parts[2]
print(pairs)
$ python3 dehydron_data_frozenset_version.py
frozenset({2, 15})
frozenset({2, 15})
Traceback (most recent call last):
File "dehydron_data_frozenset_version.py", line 35, in<module>
occurence[pair] += 1
KeyError: frozenset({2, 15})
You want to add one to "occurence[frozenset({2, 15})]" but there is no
such key in "occurence" yet.
If you carefully re-read Steven's code snippet you will see that you
missed the line
occurence[pair] = 1
in the else-branch.
Therefore "occurence[frozenset({2, 15})]" wasn't set in the first
iteration and you get the error in the second. You can see that you are
already in the second iteration by looking at the output of your program
before the error message.
Bye, Andreas
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