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Built-in Functions | Function as an Argument
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Intermediate Python: Arguments, Scopes and Decorators

Built-in FunctionsBuilt-in Functions

Here are two more examples demonstrating the use of lambda functions with the filter() and sorted() functions in Python.

Alternatively, you can pass a more complex custom function instead of a lambda to these high-order functions.

filter()

The filter() function is used to create an iterator from elements of an iterable for which a function returns true. Here's an example using filter() with a lambda function to filter out odd numbers from a list:

In this example, the lambda function lambda x: x % 2 == 0 checks if a number is even. The filter() function applies this lambda to each element in the list of numbers and returns an iterator of even numbers.

sorted()

The sorted() function returns a new sorted list from the elements of any iterable.

  • iterable is the sequence to sort (list, dict, tuple, etc);
  • key is a function to execute to decide the order;
  • reverse is a boolean. False is an ascending order, and True is descending. The default is False.

Here's an example using sorted() with a lambda function to sort a list of tuples based on the second element in each tuple:

In this example, the lambda function lambda x: x[1] returns the second element of each tuple. The sorted() function then sorts the list tuples based on these second elements, resulting in a list sorted alphabetically by the fruit names.

Task

Let's consider a list of dictionaries representing books, and you want to filter out books that have a certain number of pages.

  1. Define the list of books. books is a list of dictionaries. Each dictionary represents a book with two keys: "title" and "pages".
  2. Creating the custom function has_many_pages that accepts book and min_pages arguments.
  3. Use filter() with the custom function.
  4. Converte the filter object to a list, store it to the filtered_books_list variable, and print it.

Everything was clear?

Section 3. Chapter 3
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course content

Course Content

Intermediate Python: Arguments, Scopes and Decorators

Built-in FunctionsBuilt-in Functions

Here are two more examples demonstrating the use of lambda functions with the filter() and sorted() functions in Python.

Alternatively, you can pass a more complex custom function instead of a lambda to these high-order functions.

filter()

The filter() function is used to create an iterator from elements of an iterable for which a function returns true. Here's an example using filter() with a lambda function to filter out odd numbers from a list:

In this example, the lambda function lambda x: x % 2 == 0 checks if a number is even. The filter() function applies this lambda to each element in the list of numbers and returns an iterator of even numbers.

sorted()

The sorted() function returns a new sorted list from the elements of any iterable.

  • iterable is the sequence to sort (list, dict, tuple, etc);
  • key is a function to execute to decide the order;
  • reverse is a boolean. False is an ascending order, and True is descending. The default is False.

Here's an example using sorted() with a lambda function to sort a list of tuples based on the second element in each tuple:

In this example, the lambda function lambda x: x[1] returns the second element of each tuple. The sorted() function then sorts the list tuples based on these second elements, resulting in a list sorted alphabetically by the fruit names.

Task

Let's consider a list of dictionaries representing books, and you want to filter out books that have a certain number of pages.

  1. Define the list of books. books is a list of dictionaries. Each dictionary represents a book with two keys: "title" and "pages".
  2. Creating the custom function has_many_pages that accepts book and min_pages arguments.
  3. Use filter() with the custom function.
  4. Converte the filter object to a list, store it to the filtered_books_list variable, and print it.

Everything was clear?

Section 3. Chapter 3
toggle bottom row
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