Add a couple of exercises

Also TOC for easier navigation.

README.md

@@ -2,19 +2,48 @@
 
 :information_source:  This repo contains questions and exercises to learn and practice Python
 
-:bar_chart:  There are currently **80** exercises and questions
-
-# Python Exercises
-
+:bar_chart:  There are currently **77** exercises and questions
+
+* Exercises
+    * [Hello World](#exercises-hello-world)
+    * [Objects & Data Types](#exercises-objects)
+    * [Variables](#exercises-variables)
+    * [Booleans](#exercisese-booleans)
+    * [Strings](#exercisese-strings)
+    * [Numbers](#exercisese-numbers)
+    * [Lists and Tuples](#exercisese-lists)
+    * [Dictionaries](#exercises-dictionaries)
+    * [Loops](#exercises-loops)
+    * [Functions](#exercises-loops)
+    * [Classes](#exercises-classes)
+    * [OOP](#exercises-oop)
+* Questions
+    * [Hello World](#questions-hello-world)
+    * [Objects & Data Types](#questions-objects)
+    * [Variables](#questions-variables)
+    * [Booleans](#questions-booleans)
+    * [Strings](#questions-strings)
+    * [Numbers](#questions-numbers)
+    * [Lists and Tuples](#questions-lists)
+    * [Dictionaries](#questions-dictionaries)
+    * [Loops](#questions-loops)
+    * [Functions](#questions-loops)
+    * [Classes](#questions-classes)
+    * [OOP](#questions-oop)
+
+# Exercises
+
+<a name="exercises-hello-world"></a>
 ## Hello World
 
 |Name|Objective & Instructions|Solution|Comments|
 |--------|--------|------|----|
-| Hello World! | [Exercise](exercises/hello_world/hello_world.md) | | |
+| Hello World! | [Exercise](exercises/hello_world/hello_world.md) | Solution](solutions/hello_world/hello_world.md | |
 | Python Characteristics | [Exercise](exercises/hello_world/python_characteristics.md) | [Solution](solutions/hello_world/python_characteristics.md) | |
 | What is the result? - Level 1 | [Exercise](exercises/hello_world/what_is_the_result_lvl_1.md) | [Solution](solutions/hello_world/what_is_the_result_lvl_1.md) | |
 | What is the result? - Level 2 | [Exercise](exercises/hello_world/what_is_the_result_lvl_2.md) | | |
 
+<a name="exercises-objects"></a>
 ## Objects & Data Types
 
 |Name|Objective & Instructions|Solution|Comments|
@@ -27,6 +56,7 @@
 | Strongly Typed | [Exercise](exercises/data_types/strongly_typed.md) | [Solution](solutions/data_types/strongly_typed.md) | |
 | Object Creation | [Exercise](exercises/data_types/object_creation.md) | [Solution](solutions/data_types/object_creation.md) | |
 
+<a name="exercises-variables"></a>
 ## Variables
 
 |Name|Objective & Instructions|Solution|Comments|
@@ -38,13 +68,15 @@
 | Copying Variables | [Exercise](exercises/variables/copying_variables.md) | [Solution](solutions/variables/copying_variables.md) | |
 | Mutable Objects | [Exercise](exercises/variables/mutable_objects.md) | [Solution](solutions/variables/mutable_objects.md) | |
 
+<a name="exercises-booleans"></a>
 ## Booleans
 
 |Name|Objective & Instructions|Solution|Comments|
 |--------|--------|------|----|
 | True or False? | [Exercise](exercises/booleans/true_or_false.md) | [Solution](solutions/booleans/true_or_false.md) | |
 | Conversion | [Exercise](exercises/booleans/conversion.md) | [Solution](solutions/booleans/conversion.md) | |
 
+<a name="exercises-strings"></a>
 ## Strings
 
 |Name|Objective & Instructions|Solution|Comments|
@@ -62,6 +94,7 @@
 | Slicing - Level 1 | [Exercise](exercises/strings/slicing_lvl_1.md) | [Solution](solutions/strings/slicing_lvl_1.md) | |
 | Slicing - Level 2 | [Exercise](exercises/strings/slicing_lvl_2.md) | [Solution](solutions/strings/slicing_lvl_2.md) | |
 
+<a name="exercises-numbers"></a>
 ## Numbers
 
 |Name|Objective & Instructions|Solution|Comments|
@@ -72,6 +105,7 @@
 | Bases | [Exercise](exercises/numbers/bases.md) | [Solution](solutions/numbers/bases.md) | |
 | Palindrome | [Exercise](exercises/numbers/palindrome.md) | [Solution](solutions/numbers/palindrome.md) | |
 
+<a name="exercises-lists"></a>
 ## Lists & Tuples
 
 |Name|Objective & Instructions|Solution|Comments|
@@ -85,12 +119,14 @@
 | What is the result? - Level 1 | [Exercise](exercises/lists/what_is_the_result_lvl_1.md) | [Solution](solutions/lists/what_is_the_result_lvl_1.md) | |
 | What is the result? - Level 2 | [Exercise](exercises/lists/what_is_the_result_lvl_2.md) | [Solution](solutions/lists/what_is_the_result_lvl_2.md) | |
 
+<a name="exercises-dictionaries"></a>
 ## Dictionaries
 
 |Name|Objective & Instructions|Solution|Comments|
 |--------|--------|------|----|
 | Facts Only | [Exercise](exercises/dicts/facts_only.md) | [Solution](solutions/dict/facts_only.md) | |
 
+<a name="exercises-loops"></a>
 ## Loops
 
 |Name|Objective & Instructions|Solution|Comments|
@@ -101,6 +137,7 @@
 | Stream of Numbers | [Exercise](exercises/loops/numbers_stream.md) | [Solution](solutions/loops/numbers_stream.md) | |
 | Refactor-1 | [Exercise](exercises/loops/refactor_1.md) | [Solution](solutions/loops/refactor_1.py) | |
 
+<a name="exercises-functions"></a>
 ## Functions
 
 |Name|Objective & Instructions|Solution|Comments|
@@ -109,17 +146,20 @@
 | Calculator | [Exercise](exercises/functions/calculator.md) | [Solution](solutions/functions/calculator.md) | |
 | First Class Objects | [Exercise](exercises/functions/first_class_objects.md) | [Solution](solutions/functions/first_class_objects.md) | |
 
-## OOP
+<a name="exercises-classes"></a>
+## Classes
 
 |Name|Objective & Instructions|Solution|Comments|
 |--------|--------|------|----|
-| Inheritance | [Exercise](exercises/oop/inheritance.md) | [Solution](solutions/oop/inheritance.md) | |
+| Classes 101 | [Exercise](exercises/classes/101.md) | [Solution](solutions/classes/101.md) | |
+| Attributes  | [Exercise](exercises/classes/attributes.md) | [Solution](solutions/classes/attributes.md) | |
 
-## Classes
+<a name="exercises-oop"></a>
+## OOP
 
 |Name|Objective & Instructions|Solution|Comments|
 |--------|--------|------|----|
-| Attributes | [Exercise](exercises/classes/attributes.md) | [Solution](solutions/classes/attributes.md) | |
+| Inheritance | [Exercise](exercises/oop/inheritance.md) | [Solution](solutions/oop/inheritance.md) | |
 
 ## Magic Methods
 
@@ -186,3 +226,38 @@
 |--------|--------|------|----|
 | Random Number | [Exercise](exercises/misc/random_number.md) | | |
 | Random Item | [Exercise](exercises/misc/random_item.md) | | |
+
+# Questions
+
+<a name="questions-hello-world"></a>
+## Hello World
+
+<details>
+<summary>How to print "Hello World"?</summary><br><b>
+
+`print("Hello World")`
+</b></details>
+
+<a name="questions-classes"></a>
+## Classes
+
+<details>
+<summary>Define a class that does nothing</summary><br><b>
+
+```python
+class SomeClass:
+    pass
+```
+</b></details>
+
+<details>
+<summary>True or False? If <code>c</code> is an instance of a class, then in <code>c.x = 1</code>, <code>x</code> is a variable of the value 1</summary><br><b>
+
+False. `x` is an attribute in the case `c.x = 1`
+</b></details>
+
+<details>
+<summary>True or False? Every object in Python has attributes</summary><br><b>
+
+True. You can think on attributes as private dictionaries but instead of accessing them with `[]` or `.get`, they are accessed by using a dot.
+</b></details>

exercises/classes/101.md

@@ -0,0 +1,10 @@
+# Classes 101 - Solution
+
+## Objectives
+
+1. Define a class that does nothing and name it `SomeClass`
+2. Create an instance of the class you defined and assign it to the variable `c`
+3. True or False? In case of `c.x = 1`, `x` is a variable of value 1
+4. How to retrieve the value of `x` attribute from the previous question?
+
+Click [here to view the solution](../../solutions/classes/101.md)

exercises/classes/attributes.md

@@ -1,3 +1,7 @@
-## Attributes
+# Attributes
 
-Explain class attributes vs. instance attributes
+## Objectives
+
+1. Explain class attributes vs. instance attributes
+2. True or False? not every object in Python has attributes
+3. True or False? An attribute doesn't exist on the variable, but rather on the object that the variable refers to

exercises/hello_world/hello_world.md

@@ -2,4 +2,12 @@
 
 ## Objectives
 
-Write one line of code that will print "Hello World!"
+1. Write one line of code that will print "Hello World!"
+2. Now modify the code so the output looks like this:
+
+```
+Hello
+  World
+```
+
+Click [here to view the solution](../../solutions/hello_world.md)

exercises/hello_world/python_characteristics.md

@@ -1,5 +1,8 @@
-## Python Characteristics
+## Python Characteristics - Solution
+
+## Objectives
 
 1. What are some characteristics of the Python programming language?
+2. What type of applications use Python?
 
-Click here for the [solution](solutions/hello_world/python_characteristics.md)
+Click [here to view the solution](../../solutions/hello_world/python_characteristics.md)

exercises/variables/locations_or_names.md

@@ -2,4 +2,4 @@
 
 What do you think about the following statement:
 
-In Python, variables are locations, not just names. Each
+In Python, variables are locations, not just names. So `x = 1` is really the value of 1 in the memory location called x.

solutions/classes/101.md

@@ -0,0 +1,26 @@
+# Classes 101 - Solution
+
+## Objectives
+
+1. Define a class that does nothing and name it `SomeClass`
+2. Create an instance of the class you defined and assign it to the variable `c`
+3. True or False? In case of `c.x = 1`, `x` is a variable of value 1
+4. How to retrieve the value of `x` attribute from the previous question?
+
+## Solution
+
+1.
+
+```python
+class SomeClass:
+    pass
+```
+
+2. 
+
+```python
+c = SomeClass()
+```
+
+3. False. in `c.x`, `x` is an attribute of the instance `c` and not a variable
+4. `c.x`

solutions/classes/attributes.md

@@ -1,10 +1,14 @@
-## Attributes - Solution
+# Attributes
 
-Explain class attributes vs. instance attributes
+## Objectives
 
-### Solution
+1. Explain class attributes vs. instance attributes
+2. True or False? not every object in Python has attributes
+3. True or False? An attribute doesn't exist on the variable, but rather on the object that the variable refers to
 
-In the following block of code `x` is a class attribute while `self.y` is a instance attribute
+## Solution
+
+1. In the following block of code `x` is a class attribute while `self.y` is a instance attribute
 
 ```
 class MyClass(object):
@@ -13,3 +17,6 @@ class MyClass(object):
     def __init__(self, y):
         self.y = y
 ```
+
+2. False. Every object in Python has attributes
+3. True

solutions/hello_world/hello_world.md

@@ -0,0 +1,16 @@
+# Hello World
+
+## Objectives
+
+1. Write one line of code that will print "Hello World!"
+2. Now modify the code so the output looks like this:
+
+```
+Hello
+  World
+```
+
+## Solution
+
+1. print("Hello World!")
+2. print("Hello\n  World!")

solutions/hello_world/python_characteristics.md

@@ -1,6 +1,11 @@
-## Python Characteristics
+## Python Characteristics - Solution
+
+## Objectives
 
 1. What are some characteristics of the Python programming language?
+2. What type of applications use Python?
+
+## Solution
 
 1. 
 
@@ -11,3 +16,5 @@
 * The python package manager is called PIP "pip installs packages", having more than 200.000 available packages.
 * Python comes with pip installed and a big standard library that offers the programmer many precooked solutions.
 * In python **Everything** is an object.
+
+2. Web, Gaming, Machine Learning, Web Scrapers, Data (visualization, analytics) and more

solutions/loops/refactor_1.py

@@ -3,6 +3,7 @@
 from collections import namedtuple
 import timeit
 
+
 def before_refactor():
 
     Mushroom = namedtuple('Mushroom', ['name', 'poisonous'])
@@ -14,7 +15,8 @@ def before_refactor():
     for mushroom in mushrooms:
         i += 1
         name = mushroom.name
-        print('%d:"%s"'%(i, name))
+        print('%d:"%s"' % (i, name))
+
 
 def after_refactor():  # <- Solution is here! :)
 
@@ -26,7 +28,12 @@ def after_refactor():  # <- Solution is here! :)
     for i, mushroom in enumerate(mushrooms):
         i += 1
         name = mushroom.name
-        print('%d:"%s"'%(i, name))
+        print('%d:"%s"' % (i, name))
+
 
-print(timeit.timeit("before_refactor()", setup="from __main__ import before_refactor", number=100))
-print(timeit.timeit("after_refactor()", setup="from __main__ import after_refactor", number=100))
+print(timeit.timeit(
+    "before_refactor()",
+    setup="from __main__ import before_refactor", number=100))
+print(timeit.timeit(
+    "after_refactor()",
+    setup="from __main__ import after_refactor", number=100))

solutions/variables/locations_or_names.md

@@ -4,9 +4,11 @@
 
 What do you think about the following statement:
 
-In Python, variables are locations, not just names. Each
+In Python, variables are locations, not just names. So `x = 1` is really the value of 1 in the memory location called x.
 
 ### Solution
 
 The statement above is wrong. In Python a variable is merely a name, a reference to the object, not the actual object.
 So when for example you perform an assignment, you don't copy the value into the variable, but you assign the object with a name.
+
+So in case of `x = 1` what it means, is x refers to the integer 1.