Python Lessons – 6.3 Map and Filter

Python lessons - 6.3 Map and Filter

Map

In Python, there is a built-in function, called map(), which can be very useful for high-order functions that operate on lists. In fact, this function takes a function and an iterable object (such as a list) as arguments, and returns a new iterable object (such as a new list) with the function applied for each argument.

In the case of lists you must always use the list() function that creates a new list

if you run it, you get

The same operation could have been codified more simply using the lambda syntax, since the function is simple (it can be expressed in a single line) and it is therefore not necessary to define it, but to use it only at the moment.

Filter

Another very useful function that works on iterables is the filter () function. This function filters an iterable object by selecting only the elements that respond to a given predicate. (The predicate is a function that returns a Boolean).

if you run it, you get

⇐ Go to Python Lesson 6.2 – Lambda Functions

Go to Python Lesson 6.4 – Generators ⇒

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