create a dictionary with incrementing values

I have a list and I want to generate a dictionary d taking out duplicates and excluding a single item, such that the first key has value 0, the second has value 1, and so on.

I have written the following code:

d = {}
i = 0
for l in a_list:
    if (l not in d) and (l != '<'):
        d[l] = i
        i += 1

If a_list = ['a', 'b', '<', 'c', 'b', 'd'], after running the code d contains {'a': 0, 'b': 1, 'c': 2, 'd':3}. Order is not important. Is there a more elegant way to obtain the same result?