.. getthecode:: lambda.py
    :language: python3
    :hidden:

====================
 Lambda Expressions
====================

This page contains a memo on lambda expressions.

A lambda expressions is an anonymous function:


.. code-block:: py3

    multiply_by_two = lambda x: x*2
    
    print(multiply_by_two(2))

.. code-block:: none

    4
    
which is equivalent to


.. code-block:: py3

    def multiply_by_two(x):
        return x*2
    
But permit shorter syntactic construction like


.. code-block:: py3

    unsorted = [(x, i) for i, x in enumerate((3, 5, 4, 1, 2))]
    print(unsorted)

.. code-block:: none

    [(3, 0), (5, 1), (4, 2), (1, 3), (2, 4)]
    

.. code-block:: py3

    sorted_list = sorted(unsorted, key=lambda x: x[0])
    print(sorted_list)

.. code-block:: none

    [(1, 3), (2, 4), (3, 0), (4, 2), (5, 1)]