The original code does not return the value in the if-clause and the return statement in the else-clause, which led to the function returning None at the end of the countdown (5, 4, 3, 2, 1, 0, None).
* Update 01_selection_sort.py
Updated last print statement for Python 3 print function.
* Update 01_countdown.py
Updated print statement to print function for Python 3.
* Update 05_quicksort.py
Updated print statement to print function for Python 3.
* Update 01_price_of_groceries.py
Condensed dictionary creation into one line, edited print statement to a print function for Python 3.
* Update 01_set_covering.py
Changed print statement to print function for Python 3.
* Update 01_binary_search.py
Changed print statements to print function for Python 3.