Changed to the f' format (#377) (#396)

* Changed to the f' format (#377)

* Corrected f' statement

docs/course_materials/exercises/03_Variables_and_datatypes/class_exercise_2.md

@@ -3,5 +3,5 @@
 - Create a new file *my_full_name.py* using vim editor
 - Get the user's first name and save it in a new variable **first_name**
 - Get the user's last name and save it in a new variable **last_name**
-- Print **first_name** and **last_name** using %s formatting
+- Print **first_name** and **last_name** using `f'.{}.'` formatting
 - Save the file and run it on the terminal

docs/course_materials/variables_data_types.html

@@ -389,9 +389,9 @@ <h3><b>Formatting</b></h3>
               <pre><code data-trim data-noescape class="hljs lang-python">
     >>> name = 'Tom'
     >>> family_name = 'Sawyer'
-    >>> print('Hello %s!' % name)
+    >>> print(f'Hello {name}!')
     >>> Hello Tom!
-    >>> print('Hello %s %s!' % (name, family_name))
+    >>> print(f'Hello {name} {family_name}!')
     >>> Hello Tom Sawyer!
                     </code></pre>
             </section>