Check if a list of numbers is in a certain range?

Question

I try to discretize some numbers, by looking if they are in a given range, and then assign a number based on the range, however the result which I get is not exactly correct.

mapp is the a dictionary of which defines ranges, and the values which correspond to the given range.

lst is the list of numbers that I want to match against those ranges, and assign identifiers to them

mapp = {(0,100): 1, (100,400): 2, (400,800): 3}


lst = [3.5, 5.4, 300.12, 500.78, 600.45, 900.546]


def discretize(mapping_dict, list_of_values):
    print "\n"
    location = []
    for x in sorted(list_of_values):
        for (lower_bound,upper_bound),value in mapping_dict.items():
            if round(x) in range(lower_bound,upper_bound):
                print round(x), "yes", value

                distance = mapping_dict[(lower_bound,upper_bound)]
                location.append((distance))


        else:
            print round(x), "no"

            distance = len(mapping_dict.items())+10
            location.append((distance))

    return location

The result which I expect is: [1, 1, 2, 3, 3, 13] , however that's not what I get.

This is the actual result which I get, which is incorrect:

4.0 yes 1
4.0 no         #wrong!
5.0 yes 1
5.0 no         #wrong!
300.0 yes 2
300.0 no         #wrong!
501.0 yes 3
501.0 no         #wrong!
600.0 yes 3
600.0 no         #wrong!
901.0 no         #CORRECT

[1, 13, 1, 13, 2, 13, 3, 13, 3, 13, 13]

I get no at 4.0 which is not correct, etc, etc.

Where is the problem?

Thanks

Answer 1

mapp = {(0,100): 1, (100,400): 2, (400,800): 3}
lst = [3.5, 5.4, 300.12, 500.78, 600.45, 900.546]
result = []
for l in lst:
    for m in mapp:
        if m[0] < l < m[1]:
            result.append(mapp[m])

print result

Output:

[1, 1, 2, 3, 3]

EDIT:

result = []
for l in lst:
    flag=True
    for m in mapp:
        if m[0] < l < m[1]:
            result.append(mapp[m])
            flag = False
            break
    if flag:
        result.append(-1)
print result

Output:

[1, 1, 2, 3, 3, -1]

Answer 2

I think I have faced a similar problem once, because I found a small RangeDict class:

class RangeDict (dict):
    def __init__ (self, *args):
        super ().__init__ ()

    def __setitem__ (self, k, v):
        if not isinstance (k, slice): raise ValueError ('Indices must be slices.')
        super ().__setitem__ ( (k.start, k.stop), v)

    def __getitem__ (self, k):
        for (start, stop), v in self.items ():
            if start <= k < stop: return v
        raise IndexError ('{} out of bounds.'.format (k) )

I hope this class wraps your desired funcionality. Obviously lookup is O(N) and not O(1).

Sample usage:

r = RangeDict ()
r [0:100] = 1
r [100:400] = 2
r [400:800] = 3

for x in [3.5, 5.4, 300.12, 500.78, 600.45, 900.546]:
    print (r [x] )
#Last value raises IndexError