magic methods demo

learning_python3.md

@@ -2462,6 +2462,7 @@ for dog in all_my_dogs:
 Think of some other world objects you can create a class for and do so.
 The first one that comes to mind is vehicles but you can do anything that makes sense to you.
 
+<!---
 # Coding challenge - Bus line
 
 There is a bus line with with 20 stops on it.
@@ -2502,6 +2503,68 @@ Throughout the day 4 buses will pass by and each bus has 30 seats on it.
 **TODO**
 
 </details>
+--->
+
+## Magic methods
+
+```python
+import random
+
+
+SEXES = ["male", "female"]
+
+
+class Dog(object):
+    SOUND = "woof"
+
+    def __init__(self, name, age, sex):
+        self.name = name
+        self.age = age
+        self.sex = sex
+
+    def __str__(self):
+        if self.age > 3:
+            bark = self.__class__.SOUND.upper()
+        else:
+            bark = self.__class__.SOUND.lower()
+        return "{} barks {}".format(self.name, bark)
+
+    def __add__(self, other):
+        if self.sex == other.sex:
+            return None
+        name_part_1 = self.name[0:int(len(self.name) / 2)]
+        name_part_2 = other.name[0:int(len(self.name) / 2)]
+        name = name_part_1 + name_part_2
+        child = Dog(name, 0, random.choice(SEXES))
+        return child
+
+
+if __name__ == "__main__":
+    dog_1 = Dog("bobby", 4, SEXES[0])
+    dog_2 = Dog("molly", 4, SEXES[1])
+    dog_3= Dog("rex", 4, SEXES[0])
+    puppy = dog_1 + dog_2 + dog_3
+    print(puppy)
+    
+```
+
+```python
+class DataBase(object):
+    def __init__(self, data):
+        self.data = data 
+
+    def __iter__(self):
+        for element in self.data:
+            yield element
+
+
+if __name__ == "__main__":
+    db = DataBase(['hello', "world", "test", "one", "two"])
+    for item in db:
+        print(item)
+```
+
+* [more information](https://rszalski.github.io/magicmethods/)
 
 ## Class inheritance