Reverse Left |2|
~~~~~~~~~~~~~~~~

You are given a list of integers and a single integer from that list.
The first occurrence of that integer divides our list to 2 sub-lists,
left sub-list and right sub-list.

Write a function called *reverse_left* that takes a list of integers and
an integer in that list, and reverses the left sub-list of a given list.
The function should return a new list.

Note that the same integer can occur any number of times in the right
sub-list.

*Hint:* There are list methods for finding the first occurrence of an
element and reversing a list.

.. container:: sampleio

   Sample I/O:

.. |2| image:: ../../figures/difficulty_three.png
   :class: difficulty

.. code:: default

   >>> reverse_left([8,1,4,5,6,6,3,2], 6)
   [5,4,1,8,6,6,3,2]

   >>> reverse_left([64, 51, 77, 34, 77, 39, 57, 67, 58, 63, 51], 39)
   [77, 34, 77, 51, 64, 39, 57, 67, 58, 63, 51]

.. raw:: html

   <button type="button" class="collapsible" onclick="toggle()">

Show the Answer

.. raw:: html

   </button>

.. raw:: html

   <div class="hiddenanswer">

.. code:: python

   def reverse_left(i_list, occurrence):
       occurrence_index = i_list.index(occurrence)           #finding the index of the first occurrence

       left_sub_list = i_list[:occurrence_index]             #constructing the left sub-list
       left_sub_list.reverse()                               #reversing the left sub-list
       right_sub_list = i_list[occurrence_index:]            #constructing the right sub-list

       return left_sub_list + right_sub_list

.. raw:: html

   </div>