Python built-in Method - filter()

The filter() method is a built-in function in Python that creates an iterator from elements of an iterable for which a given function returns true. In other words, it filters out the elements from an iterable that don't meet a specified condition and returns the remaining elements.

Here is the syntax for filter() method:

filter(function, iterable)

where function is a function that takes one argument and returns a Boolean value indicating whether the argument should be included in the output, and iterable is an iterable object (such as a list or tuple) that contains the elements to be filtered.

Here's an example of how to use filter():

def is_even(num):
    return num % 2 == 0

numbers = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]

result = filter(is_even, numbers)
print(list(result))

In this example, we define a function is_even() that takes a number as input and returns True if the number is even and False otherwise. We then define a list numbers containing some integers, and call filter() with is_even and numbers. The resulting iterator is passed to the list() method, which creates a list from the iterator. The output of the code is [2, 4, 6, 8, 10], which contains only the even numbers from the numbers list.

Note that filter() returns an iterator, so if you want to get the filtered elements as a list, you need to pass the iterator to the list() method. Also, you can use a lambda function instead of defining a separate function as the first argument to filter(). For example, you can replace the is_even() function in the above code with a lambda function like this:

result = filter(lambda x: x % 2 == 0, numbers)