Python find numbers not in set

Question

I have a range of numbers such as 1-100. And I have a set that holds all, or a random subset of numbers in that range such as:

s = set([1,2,3,35,67,87,95])

What is a good way to get all of the numbers in the range 1-100 that are not in that set?

Solution 1

Use set difference operation

set(range(1, 101)) - s

Solution 2

Set difference

set(range(1, 101)) - s

Solution 3

I would add all the items not in the set into a list.

s = set([1,2,3,35,67,87,95])

x = []
for item in range(1, 101):
    if item not in s:
        x.append(item)

print x

Solution 4

Although ugly it is more efficient than set difference:

def not_in_set (s, min = 0):
    '''Returns all elements starting from min not in s.
    '''
    n = len(s)
    if n > 0:
        l = sorted(s)
        for x in range(min, l[0]):
            yield x
        for i in range(0, n - 1):
            for x in range(l[i] + 1, l[i + 1]):
                yield x
        r = l.pop() + 1
    else:
        r = min
    while True:
        yield r
        r += 1

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Comments

[matth]

Perhaps you mean range(1,101)?

[ssoler]

Readability counts. (The Zen of Python)