TypeError NoneType when performing subtraction on dict values

I have a script that does the following

subtracts values in a dict's key
convertes array to a sorted list
subtracting the first value from the second
then the second from the third
and so on.

The problem is some of the values are null in the source data and this throws a TypeError. I tried to throw in a condition but it still attempts to subtract Nones.

Here is the code with some sample data:

eLinks = {'726122193.0': [1310, 1315, 1320, 1325, 1330, 1335, 1340, 1310, 1315, 1320, 1325, 1330, 1335, 1340, 1310, 1315, 1320, 1325, 1330, 1335, 1340, 1310, 1315, 1320, 1325, 1330, 1335, 1340, 1310, 1315, 1320, 1325, 1330, 1335, 1340, 1310, 1315, 1320, 1325, 1330, 1335, 1340, 1310, 1315, 1320, 1325, 1330, 1335, 1340, 1310, 1315, 1320, 1325, 1330, 1335, 1340, 1310, 1315, 1320, 1325, 1330, 1335, 1340, 1310, 1315, 1320, 1325, 1330, 1335, 1340, 1310, 1315, 1320, 1325, 1330, 1335, 1340, 1310, 1315, 1320, 1325, 1330, 1335, 1340, 1310, 1315, 1320, 1325, 1330, 1335, 1340], '23607015.0': [None, None, None, 90, 95, 130, 2070, None, None, None, 580, 585, 610, 615, 2355, 2360, 1945, 1950, 125, 130, None, None, None, None, None, None, 90, 95, 130, 2070, None, None, None, 580, 585, 610, 615, 2355, 2360, 1945, 1950, 125, 130, None, None, None, None, None, None, 90, 95, 130, 2070, None, None, None, 580, 585, 610, 615, 2355, 2360, 1945, 1950, 125, 130, None, None, None, None, None, None, 90, 95, 130, 2070, None, None, None, 580, 585, 610, 615, 2355, 2360, 1945, 1950, 125, 130, None, None, None, None, None, None, 90, 95, 130, 2070, None, None, None, 580, 585, 610, 615, 2355, 2360, 1945, 1950, 125, 130, None, None, None, None, None, None, 90, 95, 130, 2070, None, None, None, 580, 585, 610, 615, 2355, 2360, 1945, 1950, 125, 130, None, None, None, None, None, None, 90, 95, 130, 2070, None, None, None, 580, 585, 610, 615, 2355, 2360, 1945, 1950, 125, 130, None, None, None, None, None, None, 90, 95, 130, 2070, None, None, None, 580, 585, 610, 615, 2355, 2360, 1945, 1950, 125, 130, None, None, None, None, None, None, 90, 95, 130, 2070, None, None, None, 580, 585, 610, 615, 2355, 2360, 1945, 1950, 125, 130, None, None, None, None, None, None, 90, 95, 130, 2070, None, None, None, 580, 585, 610, 615, 2355, 2360, 1945, 1950, 125, 130, None, None, None, None, None, None, 90, 95, 130, 2070, None, None, None, 580, 585, 610, 615, 2355, 2360, 1945, 1950, 125, 130, None, None, None, None, None, None, 90, 95, 130, 2070, None, None, None, 580, 585, 610, 615, 2355, 2360, 1945, 1950, 125, 130, None, None, None, None, None, None, 90, 95, 130, 2070, None, None, None, 580, 585, 610, 615, 2355, 2360, 1945, 1950, 125, 130, None, None, None]}

eOut = {}
for key, lis in eLinks.iteritems():
    eCheck = []
    sLis = sorted(lis)
    for i, _ in enumerate(sLis[:-1]):
        if i is not None:
            dif = sLis[i+1] - sLis[i]
            if dif > 20:
                eCheck.append(dif)
            eOut[key] = eCheck

Solution

You could slice away the None values after you sort, and then not worry about identifying None in the inner loop:

eOut = {}
for key, lis in eLinks.iteritems():
    eCheck = []
    sLis = sorted(lis)
    sLis = sLis[sLis.count(None):]
    for i, _ in enumerate(sLis[:-1]):
        dif = sLis[i+1] - sLis[i]
        if dif > 20:
            eCheck.append(dif)
            eOut[key] = eCheck

With your sample data, eOut becomes:

{'23607015.0': [30, 450, 25, 1330, 120, 285]}