Iterator
An iterator is an object or abstraction that provides successive values from a sequence or data source through a traversal protocol.
Learn Rust in a Month of Lunches
An iterator is a Rust value implementing the Iterator trait that produces a sequence of items, typically through repeated calls to next.
- How it is used
- Uses iterators to process collections one item at a time and compose transformations through method chains.
- How deep it goes
- Explains next(), collection iteration choices, lazy consumption, and a custom Iterator implementation; defers broader method coverage.
- Examples
- Demonstrates repeated next() calls on characters, mapped vectors, a compiler warning for unused map(), and a custom source of ones.
- What you can do after
- Build it from scratch by implementing Item and next(), or apply iterator methods to transform and collect items.
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Python How-To
An iterator is an object that produces successive items through Python's iteration protocol.
- How it is used
- Powers item-by-item for-loop processing and CSV row reading without requiring explicit iterator construction.
- How deep it goes
- Walks through iter, next, exhaustion, and StopIteration, then demonstrates automatic for-loop handling; stops short of implementing a custom iterator.
- Examples
- Traces a three-item list iterator and consumes a CSV header before processing the remaining rows.
- What you can do after
- Apply it via Python's iter, next, and csv.reader to consume elements or rows one at a time.
Python Workout: 50 ten-minute exercises
An iterator is an object that provides successive elements of an iterable, typically one element at a time.
- How it is used
- Uses iterators to make objects work naturally with for loops and to process collections or computed sequences incrementally.
- How deep it goes
- Explains protocol methods, stored iteration state, exhaustion, reusable helper iterators, and generator alternatives.
- Examples
- Demonstrates custom classes, repeated iteration, circular data, enumerate, generator expressions, and lazy file transformation.
- What you can do after
- Builds custom iterables, writes generators, chooses reusable iterator designs, and processes data with less memory.
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100 Java Mistakes and How to Avoid Them
An iterator is an object that traverses the elements of a collection and can optionally remove elements through its iteration protocol.
- How it is used
- Guides safe traversal and removal in mutable Java collections and custom Iterable implementations.
- How deep it goes
- Explains iterator call contracts, fail-fast modification checks, and corrected range and reader implementations without detailing collection internals beyond modCount.
- Examples
- Uses a numeric range, buffered reader, conditional list filtering, and list mutation during enhanced for traversal.
- What you can do after
- Diagnose/debug with it by avoiding skipped elements, concurrent modifications, and custom iterators that fail outside enhanced for loops.
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Go by Example
An iterator is an abstraction that lets a consumer retrieve values from a sequence one at a time through a standardized interface.
- How it is used
- Standardizes incremental consumption of multiple request results while hiding sequential or concurrent production.
- How deep it goes
- Explains custom push iterators through `iter.Seq`, yield control, production, consumption, and tests; defers deeper iterator history externally.
- Examples
- Builds `Results`, `SendN`, and `Summarize`, then tests fastest-result calculation and nil-iterator handling with `slices.Values`.
- What you can do after
- Apply it via Go `iter.Seq` to produce and consume request results incrementally with early stopping.
Idiomatic Rust
An iterator is an abstraction that produces a sequence of values one element at a time according to a traversal protocol.
- How it is used
- Uses iterators to traverse data structures and express operations through a fluent interface.
- How deep it goes
- Works from the Iterator trait’s required Item and next() to a linked-list implementation and append example.
- Examples
- Demonstrates a linked-list iterator whose last() method locates the node used for append().
- What you can do after
- Build it from scratch by implementing Iterator for a linked list and using its provided methods.
Python Workout, Second Edition
The iterator protocol is the Python protocol through which an object supplies successive values for iteration.
- How it is used
- Supports for loops, comprehensions, and functions that consume successive values from iterable objects.
- How deep it goes
- Defines __iter__, __next__, and StopIteration, then works through iterator state, helper classes, generators, and exhaustion behavior.
- Examples
- Uses strings, lists, dictionaries, files, a repeating Circle iterator, and a multi-file line generator as concrete cases.
- What you can do after
- Build iterable classes, helper iterators, generator functions, and generator expressions, then diagnose exhausted or non-iterable loop targets.
The Joy of JavaScript
An iterator object is an object that implements the iterator protocol by providing a next method that produces iteration results.
- How it is used
- Enables objects and generated sequences to control how values are delivered to JavaScript consumers.
- How deep it goes
- Defines the `next()` result contract, explains malformed results, and demonstrates custom implementations.
- Examples
- Uses random-number sequences, blockchain blocks and transactions, and strings as iteration examples.
- What you can do after
- Build it from scratch by implementing `next()` results, then enable `for...of` with `Symbol.iterator`.
Secrets of the JavaScript Ninja, Second Edition
An object that produces a sequence of values one at a time through an iteration protocol, typically using a next method.
- How it is used
- Uses iterators to request values from generators and to consume generated sequences with for...of.
- How deep it goes
- Traces next() through yield, suspension, and value/done results, without generalizing beyond generator-created iterators.
- Examples
- Demonstrates weapon sequences, generated IDs, and generator-based traversal of a DOM tree.
- What you can do after
- Apply generator iterators with next() or for-of to request sequence values and traverse DOM nodes.
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Software Design for Python Programmers
An iterator is an object or interface that provides sequential access to elements of a collection without exposing the collection's implementation.
- How it is used
- Separates one algorithm from multiple sequential collection representations through delegated traversal.
- How deep it goes
- Defines iterator responsibilities, concrete implementations, client delegation, and extensibility, while stopping short of broader iterator internals.
- Examples
- Uses baseball-team player reports backed by a list, generator, and dictionary, with ListIterator, GeneratorIterator, and DictionaryIterator.
- What you can do after
- Build it from scratch by defining an iterator interface, pairing implementations with collections, and delegating traversal to the client.
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Object-Oriented Software Design in C++
An iterator is an abstraction that provides sequential access to elements of a data structure without exposing its representation.
- How it is used
- Separates one processing algorithm from multiple sequential collection representations.
- How deep it goes
- Explains interfaces, cursors, delegation, and traversal code, while stopping short of a broader implementation treatment.
- Examples
- Uses baseball team reports over array-, vector-, and map-based Player collections.
- What you can do after
- Build it from scratch by defining iterator operations, storing traversal state, and delegating collection-specific iteration.
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The Quick Python Book, Fourth Edition
An iterator is an object that provides successive values through the iteration protocol until its values are exhausted.
- How it is used
- Supplies values to loops and consumers such as CSV writers, including file lines and paired data.
- How deep it goes
- Defines successive values until exhaustion and demonstrates file and zip() iteration without detailing protocol mechanics.
- Examples
- Demonstrates counting file lines and writing paired weather dates and temperatures to CSV.
- What you can do after
- Apply it via for loops and csv.writerows() to process file lines or paired lists.
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100 C++ Mistakes and How to Avoid Them
An iterator is a C++ library object that provides a uniform means of traversing and accessing elements in a range or container.
- How it is used
- Uses iterators to search containers and traverse elements without imposing an index-based interface.
- How deep it goes
- Explains declaration, increment, dereference, end comparison, and container variation, but does not develop iterator internals.
- Examples
- Demonstrates key lookup with std::find and summation through vector and set iterators.
- What you can do after
- Apply it via STL algorithms and container loops to search or process elements while avoiding array-size bookkeeping.
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The Well-Grounded Rubyist, Fourth Edition
An iterator is a method or construct that automatically traverses the elements of a collection.
- How it is used
- Uses methods that yield to supplied blocks to repeat work or process collection values.
- How deep it goes
- Explains block-and-yield mechanics and contrasts iterators with stateful enumerators, without detailing every iterator's implementation.
- Examples
- Uses loop with puts and String#each_byte to demonstrate block-based iteration and blockless calls.
- What you can do after
- Apply iterators by supplying a block, or call many built-in iterators without one to obtain an enumerator.
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Functional Programming in JavaScript
- How it is used
- Supports lazy traversal when callers need values incrementally or may stop before exhausting a data source.
- How deep it goes
- Explains internal iterator state, protocol methods, generator suspension, and for...of consumption.
- Examples
- Uses infinite ranges, bounded ranges, square generation, string iteration, and recursive tree traversal.
- What you can do after
- Build it from scratch with Symbol.iterator and next, or consume generators through for...of.
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Related concepts
- loopused by · A loop is a programming control-flow construct that repeatedly executes a block of instructions according to an iteration rule or continuation condition.
- data transformationproduced by · A data transformation is an operation or function that maps input data or its representation to modified data or a different representation.
- file objectincludes · A file object is a program-accessible representation of an open file or stream, including its access state and input/output operations.
- __iter__produced by · __iter__ is a Python special method that returns an iterator for an object.
- generatorincludes · A generator is a language construct or computation that produces values incrementally on demand, typically suspending and resuming while preserving its state.
- __next__has part · __next__ is a Python special method that returns an iterator’s next item or raises StopIteration when no items remain.
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