> Im trying to iterate through values in a dictionary so i can find the
> closest value and then extract the key for that value....what ive done so far:
>
> def pcloop(dictionary, exvalue):
> z = dictionary.itervalues()
> y = z - exvalue
> v = (y*y)**1/2
> if v < 0.001:
> u = dictionary.get[z]
> return u
I think I understand what you're trying to do...given a target
value, find the key/value pair in your dictionary where your
value is closest to the target...where "closest" is defined by
absolute-value difference between the target and the value.
Below I've included two such functions that do about the same
thing (the difference being kind behavior in the first if the
dataset is an empty dictionary, compared to just blowing up as
the second one does). The first findClosest function is verbose,
but helps you understand what it's doing. The second is, um,
more succinct (read "deathly near opaque, and would probably get
you shot for using it in a production environment").
Both return a tuple containing the key into the dataset and its
associated value.
-tkc
def findClosest(dataset, target):
closest_value = None
closest_key = None
closest_distance = None
for k,v in dataset.items():
distance = (target - v) ** 2
if closest_value:
if distance < closest_distance:
closest_key = k
closest_value = v
closest_distance = distance
else:
closest_key = k
closest_value = v
closest_distance = distance
return closest_key, closest_value
def findClosest2(dataset, target):
return reduce(
lambda x,y:
((target - y[1]) ** 2 <
(target - x[1]) ** 2)
and y or x, dataset.items())
if __name__ == '__main__':
sample_data = {'a':1,
'b':3,
'c':6}
target = 4
print findClosest(sample_data, target)
print findClosest2(sample_data, target)
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