![]() ![]() It is used to iterate over any sequences such as list, tuple, string, etc. In Python, the for loop is used to run a block of code for a certain number of times. It's just a simple example you can achieve much more with loops. You saw earlier that an iterator can be obtained from a dictionary with iter(), so you know dictionaries must be iterable.In computer programming, loops are used to repeat a block of code.įor example, if we want to show a message 100 times, then we can use a loop. It’s elegant in its simplicity and eminently versatile. They can all be the target of a for loop, and the syntax is the same across the board. You will discover more about all the above throughout this series. Python features a construct called a generator that allows you to create your own iterator in a simple, straightforward way. User-defined objects created with Python’s object-oriented capability can be made to be iterable. There is a Standard Library module called itertools containing many functions that return iterables. Many built-in and library objects are iterable. Python treats looping over all iterables in exactly this way, and in Python, iterables and iterators abound: Perhaps this seems like a lot of unnecessary monkey business, but the benefit is substantial. This sequence of events is summarized in the following diagram: Schematic Diagram of a Python for Loop The loop body is executed once for each item next() returns, with loop variable i set to the given item for each iteration. Terminates the loop when next() raises the StopIteration exception.Calls next() repeatedly to obtain each item from the iterator in turn.Calls iter() to obtain an iterator for a.To carry out the iteration this for loop describes, Python does the following: This loop can be described entirely in terms of the concepts you have just learned about. Here is an example using the same list as above: The built-in function next() is used to obtain the next value from in iterator. Once you’ve got an iterator, what can you do with it?Īn iterator is essentially a value producer that yields successive values from its associated iterable object. Okay, now you know what it means for an object to be iterable, and you know how to use iter() to obtain an iterator from it. (You will find out how that is done in the upcoming article on object-oriented programming.) Iterators Even user-defined objects can be designed in such a way that they can be iterated over. In fact, almost any object in Python can be made iterable. As you will see soon in the tutorial on file I/O, iterating over an open file object reads data from the file. ![]() For example, open files in Python are iterable. Many objects that are built into Python or defined in modules are designed to be iterable. These include the string, list, tuple, dict, set, and frozenset types.īut these are by no means the only types that you can iterate over. > iter ( 42 ) # Integer Traceback (most recent call last):įile "", line 1, in iter ( 42 ) TypeError: 'int' object is not iterable > iter ( 3.1 ) # Float Traceback (most recent call last):įile "", line 1, in iter ( 3.1 ) TypeError: 'float' object is not iterable > iter ( len ) # Built-in function Traceback (most recent call last):įile "", line 1, in iter ( len ) TypeError: 'builtin_function_or_method' object is not iterableĪll the data types you have encountered so far that are collection or container types are iterable. Then you will learn about iterables and iterators, two concepts that form the basis of definite iteration in Python.įinally, you’ll tie it all together and learn about Python’s for loops. You’ll start with a comparison of some different paradigms used by programming languages to implement definite iteration. Here’s what you’ll cover in this tutorial: In Python, indefinite iteration is performed with a while loop.Indefinite iteration, in which the code block executes until some condition is met.Definite iteration, in which the number of repetitions is specified explicitly in advance.Repetitive execution of the same block of code over and over is referred to as iteration. ![]() In the previous tutorial in this introductory series, you learned the following: This tutorial will show you how to perform definite iteration with a Python for loop. Watch it together with the written tutorial to deepen your understanding: For Loops in Python (Definite Iteration) ![]() Watch Now This tutorial has a related video course created by the Real Python team. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |