How to see if the list contains consecutive numbers

Question

I want to test if a list contains consecutive integers and no repetition of numbers. For example, if I have

l = [1, 3, 5, 2, 4, 6]

It should re

Answer 1

The first code removes duplicates but keeps order:

from itertools import groupby, count

l = [1,2,4,5,2,1,5,6,5,3,5,5]

def remove_duplicates(values):
    output = []
    seen = set()
    for value in values:
        if value not in seen:
            output.append(value)
            seen.add(value)
    return output

l = remove_duplicates(l) # output = [1, 2, 4, 5, 6, 3]

The next set is to identify which ones are in order, taken from here:

def as_range(iterable):
    l = list(iterable)
    if len(l) > 1:
        return '{0}-{1}'.format(l[0], l[-1])
    else:
        return '{0}'.format(l[0])

l = ','.join(as_range(g) for _, g in groupby(l, key=lambda n, c=count(): n-next(c)))

l outputs as: 1-2,4-6,3

You can customize the functions depending on your output.