Lazy sorter - an iterator that yields items in sorted order, lazily

lazyquicksort.py

from itertools import tee

def lazy_sort(v, key=lambda x: x):
    v = iter(v)
    try:
        pivot = next(v)
    except StopIteration:
        return
    v_pre, v_pos = tee(v)
    yield from lazy_sort((item for item in v_pre if key(item) < key(pivot)), key)
    yield pivot
    yield from lazy_sort((item for item in v_pos if key(item) >= key(pivot)), key)
    

lazyquicksort_extradict.py

"""
This is exactly the same as above - but using the fresh "extradict.Grouper" class,
published with extradict 0.5.0;
(Actually, when writting the snippet above I missed this "tee like" functionality,
and wrote the new class in the package)
"""

from itertools import tee
from extradict import Grouper

def lazy_sort(v, key=lambda x: x):
    v = iter(v)
    try:
        pivot = next(v)
    except StopIteration:
        return
    kpivot = key(pivot)
    groups = Grouper(v, key= lambda item: key(item) < kpivot)
    yield from lazy_sort(groups.get(True, ()), key=key)
    yield pivot
    yield from lazy_sort(groups.get(False, ()), key=key)