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...iterator types support a __copy__ method (if and only if it can be implemented with small costs in memory and runtime, and produce an independently-iterable copy of an iterator object), this PEP's implementation will specifically include the addition of copyability to the iterators over sequences that built-in iter returns, and also to the iterators over a dictionary returned by the methods __iter__, iterkeys, itervalues, and iteritems of built-in type dict. Iterators produced by generator funct...
...iter or tp_iternext slots. The macro PyIter_Check() tests whether an object has the appropriate flag set and has a non-NULL tp_iternext slot. There is no such macro for the tp_iter slot (since the only place where this slot is referenced should be PyObject_GetIter(), and this can check for the Py_TPFLAGS_HAVE_ITER flag directly). (Note: the tp_iter slot can be present on any object; the tp_iternext slot should only be present on objects that act as iterators.) For backwards compatibility, the P...
...iteration operation depends on two helper functions for efficient iteration over mapping values and mapping item tuples: d.keys() -> list(d) d.values() -> list(itervalues(d)) d.items() -> list(iteritems(d)) d.iterkeys() -> iter(d) d.itervalues() -> itervalues(d) d.iteritems() -> iteritems(d) Both six and future.utils provide appropriate definitions of itervalues() and iteritems() (along with essentially redundant definitions of iterkeys()). Creating your own definitions of th...
...iters]) def __iterclose__(self): map_chaining_exceptions(operator.iterclose, self._iters) def chain(*iterables): try: while iterables: for element in iterables.pop(0): yield element except BaseException as e: def iterclose_iterable(iterable): operations.iterclose(iter(iterable)) map_chaining_exceptions(iterclose_iterable, iterables, last_exc=e) In some cases this requires some subtlety; for example, itertools....
...iteration arises because the tail of the underlying list is altered during iteration. Rejected Alternatives Several variants were submitted that attempted to apply reversed() to all iterables by running the iterable to completion, saving the results, and then returning a reverse iterator over the results. While satisfying some notions of full generality, running the input to the end is contrary to the purpose of using iterators in the first place. Also, a small disaster ensues if the underl...
...iterator behavior has to be a bit more subtle to handle the case of either the right or left iterator raising SuspendIteration. It seems to be a matter of decomposing the generator to recognize intermediate states where a SuspendIterator exception from the producing context could happen. class pair: def __init__(self, iterLeft, iterRight): self.iterLeft = iterLeft self.iterRight = iterRight def __iter__(self): self.rhs = iter(iterRight) self.lhs = iter...
...iter" when called with an instance of types.intType as the argument. The returned iterator has the following behavior: Assume that object i is an instance of types.intType (the builtin type int) and that i > 0 iter(i) returns an iterator object said iterator object iterates through the sequence of ints 0,1,2,...,i-1 Example: iter(5) returns an iterator object that iterates through the sequence of ints 0,1,2,3,4 if i <= 0, iter(i) returns an "empty" iterator, i.e., one that throws Sto...
...iterable collections with the same advantage that iteritems() affords to dictionaries -- a compact, readable, reliable index notation. Rationale Python 2.2 introduced the concept of an iterable interface as proposed in PEP 234. The iter() factory function was provided as common calling convention and deep changes were made to use iterators as a unifying theme throughout Python. The unification came in the form of establishing a common iterable interface for mappings, sequences, and file obje...
...iterator created by the first @ could easily be taught how to combine itself with ordinary iterators. There would have to be some way to distinguish restartable iterators from ones that couldn't be restarted. For example, if S is an input stream (e.g. a file), and L is a list, then S @ L is straightforward, but L @ S is not, since iteration through the stream cannot be repeated. This could be treated as an error, or by having the outer iterator detect non-restartable inner iterators and cache...
From 22 Oct. through 30 Oct., 2022
Location: Online, New Zealand
Smart Iterator Challenge-week 3, New Zealand Python User Group - Auckland
From 08 Oct. through 16 Oct., 2022
Smart Iterator Challenge-week 2, New Zealand Python User Group - Auckland
...iterator, which it will in Python 3.0)." Rationale One of the most common uses of for-loops in Python is to iterate over an interval of integers. Python provides functions range() and xrange() to generate lists and iterators for such intervals, which work best for the most frequent case: half-open intervals increasing from zero. However, the range() syntax is more awkward for open or closed intervals, and lacks symmetry when reversing the order of iteration. In addition, the call to an unfa...
...iteration protocol defined in PEP 492. It is a SyntaxError to have a non-empty return statement in an asynchronous generator. Support for Asynchronous Iteration Protocol The protocol requires two special methods to be implemented: An __aiter__ method returning an asynchronous iterator. An __anext__ method returning an awaitable object, which uses StopIteration exception to "yield" values, and StopAsyncIteration exception to signal the end of the iteration. Asynchronous generators define both...
...iteration of finishable iterators Partial iteration of a finishable iterator is possible, although it requires some care to ensure the iterator is still finalised promptly (it was made finishable for a reason!). First, we need a class to enable partial iteration of a finishable iterator by hiding the iterator's __finish__() method from the for loop: class partial_iter(object): def __init__(self, iterable): self.iter = iter(iterable) def __iter__(self): return self ...
...iters) 0.000001 seconds threaded (1 threads) 0.000796 seconds processes (1 procs) 0.000714 seconds non_threaded (2 iters) 0.000002 seconds threaded (2 threads) 0.001963 seconds processes (2 procs) 0.001466 seconds non_threaded (4 iters) 0.000002 seconds threaded (4 threads) 0.003986 seconds processes (4 procs) 0.002701 seconds non_threaded (8 iters) 0.000003 seconds threaded (8 threads) 0.007990 seconds processes (8 procs) 0.005512 seconds As you can see, proc...
...Iterable Unpacking PEP:3132 Title:Extended Iterable Unpacking Author:Georg Brandl <georg at python.org> Status:Final Type:Standards Track Created:30-Apr-2007 Python-Version:3.0 Post-History: Contents Abstract Rationale Specification Implementation Grammar change Changes to the Compiler Changes to the Bytecode Interpreter Acceptance References Copyright Abstract This PEP proposes a change to iterable unpacking syntax, allowing to specify a "catch-all" name which will...
...iterator to decide whether a block-statement represents a loop with multiple iterations; in the most common use case BLOCK1 is executed exactly once. To the parser, however, it is always a loop; break and continue return transfer to the block's iterator (see below for details). The translation is subtly different from a for-loop: iter() is not called, so EXPR1 should already be an iterator (not just an iterable); and the iterator is guaranteed to be notified when the block-statement is left, re...
...iterables, strict=False): if not iterables: return iterators = tuple(iter(iterable) for iterable in iterables) try: while True: items = [] for iterator in iterators: items.append(next(iterator)) yield tuple(items) except StopIteration: if not strict: return if items: i = len(items) plural = " " if i == 1 else "s 1-" msg = f"zip() argument {i+1} is shorter than argum...
...iterators and iterator methods This is a variant of Proposal D. Iterators would need be created explicitly if anything other that the most basic use of break and continue was required. Instead of modifying the syntax of break and continue, .break() and .continue() methods could be added to the Iterator type. a_iter = iter(a_list) for a in a_iter: ... b_iter = iter(b_list) for b in b_iter: ... if condition_one(a,b): b_iter.break() # same as plain old br...
...iterator protocol in Python 2.x consists of two methods: __iter__() called on an iterable object to yield an iterator, and next() called on an iterator object to yield the next item in the sequence. Using a for loop to iterate over an iterable object implicitly calls both of these methods. This PEP proposes that the next method be renamed to __next__, consistent with all the other protocols in Python in which a method is implicitly called as part of a language-level protocol, and that a built-...