Most Pythonic Way to Split an Array by Repeating Elements

Question

I have a list of items that I want to split based on a delimiter. I want all delimiters to be removed and the list to be split when a delimiter occurs twice. F

Answer 1

Here's a clean nice solution using zip and generators

#1 define traditional sequence split function 
#if you only want it for lists, you can use indexing to make it shorter
def split(it, x):
    to_yield = []
    for y in it:
        if x == y:
            yield to_yield
            to_yield = []
        else:
            to_yield.append(y)
    if to_yield:
        yield to_yield

#2 zip the sequence with its tail 
#you could use itertools.chain to avoid creating unnecessary lists
zipped = zip(l, l[1:] + [''])

#3. remove ('X',not 'X')'s from the resulting sequence, and leave only the first position of each
# you can use list comprehension instead of generator expression
filtered = (x for x,y in zipped if not (x == 'X' and y != 'X'))

#4. split the result using traditional split
result = [x for x in split(filtered, 'X')]

This way split() is more reusable.

It's surprising python doesn't have one built in.

edit:

You can easily adjust it for longer split sequences, repeating steps 2-3 and zipping filtered with l[i:] for 0< i <= n.