Module: itertools

반복자에 관한 함수들이 들어있는 모듈: itertools 

Source: https://docs.python.org/3.7/library/itertools.html#itertools.groupby

무한 반복자:

반복자	인수	결과	예
count()	start, [step]	start, start+step, start+2*step, …	count(10) --> 10 11 12 1314 ...
cycle()	p	p0, p1, … plast, p0, p1, …	cycle('ABCD') --> A B C DA B C D ...
repeat()	elem [,n]	elem, elem, elem, … endlessly or up to n times	repeat(10, 3) --> 10 10 10

Iterators terminating on the shortest input sequence:

반복자	인수	결과	예
accumulate()	p [,func]	p0, p0+p1, p0+p1+p2, …	accumulate([1,2,3,4,5]) -->1 3 6 10 15
chain()	p, q, …	p0, p1, … plast, q0, q1, …	chain('ABC', 'DEF') --> A BC D E F
chain.from_iterable()	iterable	p0, p1, … plast, q0, q1, …	chain.from_iterable(['ABC','DEF']) --> A B C D E F
compress()	data, selectors	(d[0] if s[0]), (d[1] if s[1]), …	compress('ABCDEF',[1,0,1,0,1,1]) --> A C E F
dropwhile()	pred, seq	seq[n], seq[n+1], starting when pred fails	dropwhile(lambda x: x<5,[1,4,6,4,1]) --> 6 4 1
filterfalse()	pred, seq	elements of seq where pred(elem) is false	filterfalse(lambda x: x%2,range(10)) --> 0 2 4 6 8
groupby()	iterable[, key]	sub-iterators grouped by value of key(v)
islice()	seq, [start,] stop [, step]	elements from seq[start:stop:step]	islice('ABCDEFG', 2, None)--> C D E F G
starmap()	func, seq	func(*seq[0]), func(*seq[1]), …	starmap(pow, [(2,5), (3,2),(10,3)]) --> 32 9 1000
takewhile()	pred, seq	seq[0], seq[1], until pred fails	takewhile(lambda x: x<5,[1,4,6,4,1]) --> 1 4
tee()	it, n	it1, it2, … itn splits one iterator into n
zip_longest()	p, q, …	(p[0], q[0]), (p[1], q[1]), …	zip_longest('ABCD', 'xy',fillvalue='-') --> Ax By C-D-

조합 반복자:

Iterator	Arguments	Results
product()	p, q, … [repeat=1]	cartesian product, equivalent to a nested for-loop
permutations()	p[, r]	r-length tuples, all possible orderings, no repeated elements
combinations()	p, r	r-length tuples, in sorted order, no repeated elements
combinations_with_replacement()	p, r	r-length tuples, in sorted order, with repeated elements
product('ABCD', repeat=2)		AA AB AC AD BA BB BC BD CA CB CCCD DA DB DC DD
permutations('ABCD', 2)		AB AC AD BA BC BD CA CB CD DA DBDC
combinations('ABCD', 2)		AB AC AD BC BD CD
combinations_with_replacement('ABCD',2)		AA AB AC AD BB BC BD CC CD DD