If predicate is None, return the itemsĭef imap ( function, * iterables ): # imap(pow, (2,3,10), (5,2,3)) -> 32 9 1000 iterables = map ( iter, iterables ) while True : args = if function is None : yield tuple ( args ) else : yield function ( * args ) itertools. Make an iterator that filters elements from iterable returning only those for tgtkey )) def _grouper ( self, tgtkey ): while self. currvalue = object () def _iter_ ( self ): return self def next ( self ): while self. Is needed later, it should be stored as a list:Ĭlass groupby ( object ): # -> A B C D A B # -> AAAA BBB CC D def _init_ ( self, iterable, key = None ): if key is None : key = lambda x : x self. Object is advanced, the previous group is no longer visible. Because the source is shared, when the groupby() The returned group is itself an iterator that shares the underlying iterable That behavior differs from SQL’s GROUP BY which aggregates commonĮlements regardless of their input order. (which is why it is usually necessary to have sorted the data using the same keyįunction). Generates a break or new group every time the value of the key function changes The operation of groupby() is similar to the uniq filter in Unix. Generally, the iterable needs to already be sorted on Specified or is None, key defaults to an identity function and returns The key is a function computing a key value for each element. Make an iterator that returns consecutive keys and groups from the iterable. R-length tuples, in sorted order, no repeated elementsĭef dropwhile ( predicate, iterable ): # dropwhile(lambda x: x 6 4 1 iterable = iter ( iterable ) for x in iterable : if not predicate ( x ): yield x break for x in iterable : yield x itertools. R-length tuples, all possible orderings, no repeated elements Izip_longest('ABCD', 'xy', fillvalue='-') -> Ax By C- D-Ĭartesian product, equivalent to a nested for-loop Ifilter(lambda x: x%2, range(10)) -> 1 3 5 7 9Įlements of seq where pred(elem) is False Sub-iterators grouped by value of keyfunc(v) Iterators terminating on the shortest input sequence: Iterator Sum(imap(operator.mul, vector1, vector2)).Įlem, elem, elem. Operator can be mapped across two vectors to form an efficient dot-product: These tools and their built-in counterparts also work well with the high-speedįunctions in the operator module. The same effect can be achieved in Pythonīy combining imap() and count() to form imap(f, count()). Together, they form an “iteratorĪlgebra” making it possible to construct specialized tools succinctly andįor instance, SML provides a tabulation tool: tabulate(f) which produces a The module standardizes a core set of fast, memory efficient tools that are This module implements a number of iterator building blocks inspiredīy constructs from APL, Haskell, and SML. itertools - Functions creating iterators for efficient looping ¶
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