adds currency converter

learning_python3.md

@@ -440,6 +440,38 @@ else:
 
 </details>
 
+# Coding challenge - Currency converter
+
+I would like you to write a program that converts EUR to DOLLAR.
+You should do this in a **new** python file.
+I suggest you call it `euro_to_dollar.py` or something that makes sense to you.
+The result of this program *could* be as follows.
+
+```bash
+➜  python_course_doc git:(master) ✗ python3 test.py                  
+How much EUR would you like to convert into DOLLAR? 140
+140 EUR is 159.6 DOLLAR
+➜  python_course_doc git:(master) ✗ python3 test.py
+How much EUR would you like to convert into DOLLAR? blablabla
+That's not a number I understand...
+➜  python_course_doc git:(master) ✗ 
+```
+<details>
+  <summary>Spoiler warning</summary>
+result = input("How much EUR would you like to convert into DOLLAR? ")
+
+rate = 1.14
+
+if result.isdigit():
+    eur = int(result)
+    dollar = eur * rate
+    print("{} EUR is {} DOLLAR".format(eur, dollar))
+else:
+    print("That's not a number I understand...")
+
+</details>
+
+
 # A text based adventure game
 
 We can use conditional logic to create quite elaborate decision processes.
@@ -1712,6 +1744,12 @@ for login in my_login_list:
         print("\t{}: {}".format(key, login[key]))
 ```
 
+🏃 Try it
+---
+
+Go back to you *currency converter* program and add a `dict` with multiple currencies so you can enter one amount to convert and your program gives you how much that is in each currency of the `dict`.
+
+
 # Coding challenge - Task manager
 
 Can you create me a *task manager* please?