Question

I want to remove all elements from a list I want to iterate over a list, skipping elements that match some test, and a certain number of elements after that match. eg.

# skip 'foo' and 2 subsequent values

values = [1, 2, 3, 'foo', 'a', 'b', 6, 7, 'foo', 'x', 'y']

result = [1, 2, 3, 6, 7]

Is there a more elegant method to achieve this than iterating using a counter building a new list and skipping forwards n iteratations when the match is found? ie.

values = [1, 2, 3, 'foo', 'a', 'b', 6, 7, 'foo', 'x', 'y']

result = []

i = 0
while i < len(values):
    if values[i] == 'foo':
        i += 3
    else:
        result.append(values[i])
        i += 1

print result

[1, 2, 3, 6, 7]

Answer 1

Hmm, how about a generator?

def iterskip(iterator, test, n):
    """Iterate skipping values matching test, and n following values"""
    iterator = iter(iterator)
    while 1:
        value = next(iterator)
        if test(value):
            for dummy in range(n):
                next(iterator)
        else:
            yield value

def is_foo(value):
    return value == 'foo'

print list(iterskip(values, is_foo, 2))