add DRY example

README.md

@@ -750,7 +750,143 @@ print(person.name_as_first_and_last)  # => ["Ryan", "McDermott"]
 
 ## **Don't repeat yourself (DRY)**
 
-*Coming soon*
+Try to observe the [DRY](https://en.wikipedia.org/wiki/Don%27t_repeat_yourself) principle.
+
+Do your absolute best to avoid duplicate code. Duplicate code is bad because
+it means that there's more than one place to alter something if you need to
+change some logic.
+
+Imagine if you run a restaurant and you keep track of your inventory: all your
+tomatoes, onions, garlic, spices, etc. If you have multiple lists that
+you keep this on, then all have to be updated when you serve a dish with
+tomatoes in them. If you only have one list, there's only one place to update!
+
+Often you have duplicate code because you have two or more slightly
+different things, that share a lot in common, but their differences force you
+to have two or more separate functions that do much of the same things. Removing
+duplicate code means creating an abstraction that can handle this set of different
+things with just one function/module/class.
+
+Getting the abstraction right is critical. Bad abstractions can be
+worse than duplicate code, so be careful! Having said this, if you can make
+a good abstraction, do it! Don't repeat yourself, otherwise you'll find yourself
+updating multiple places any time you want to change one thing.
+
+**Bad:**
+
+```python
+from typing import List, Text, Dict
+from dataclasses import dataclass
+
+@dataclass
+class Developer:
+    def __init__(self, experience: float, github_link: Text) -> None:
+        self._experience = experience
+        self._github_link = github_link
+
+    @property
+    def experience(self) -> float:
+        return self._experience
+
+    @property
+    def github_link(self) -> Text:
+        return self._github_link
+
+@dataclass
+class Manager:
+    def __init__(self, experience: float, github_link: Text) -> None:
+        self._experience = experience
+        self._github_link = github_link
+
+    @property
+    def experience(self) -> float:
+        return self._experience
+
+    @property
+    def github_link(self) -> Text:
+        return self._github_link
+
+
+def get_developer_list(developers: List[Developer]) -> List[Dict]:
+    developers_list = []
+    for developer in developers:
+        developers_list.append({
+        'experience' : developer.experience,
+        'github_link' : developer.github_link
+            })
+    return developers_list
+
+def get_manager_list(managers: List[Manager]) -> List[Dict]:
+    managers_list = []
+    for manager in managers:
+        managers_list.append({
+        'experience' : manager.experience,
+        'github_link' : manager.github_link
+            })
+    return managers_list
+
+## create list objects of developers
+company_developers = [
+    Developer(experience=2.5, github_link='https://github.com/1'),
+    Developer(experience=1.5, github_link='https://github.com/2')
+]
+company_developers_list = get_developer_list(developers=company_developers)
+
+## create list objects of managers
+company_managers = [
+    Manager(experience=4.5, github_link='https://github.com/3'),
+    Manager(experience=5.7, github_link='https://github.com/4')
+]
+company_managers_list = get_manager_list(managers=company_managers)
+```
+
+**Good:**
+
+```python
+from typing import List, Text, Dict
+from dataclasses import dataclass
+
+@dataclass
+class Employee:
+    def __init__(self, experience: float, github_link: Text) -> None:
+        self._experience = experience
+        self._github_link = github_link
+
+    @property
+    def experience(self) -> float:
+        return self._experience
+
+    @property
+    def github_link(self) -> Text:
+        return self._github_link
+
+
+
+def get_employee_list(employees: List[Employee]) -> List[Dict]:
+    employees_list = []
+    for employee in employees:
+        employees_list.append({
+        'experience' : employee.experience,
+        'github_link' : employee.github_link
+            })
+    return employees_list
+
+## create list objects of developers
+company_developers = [
+    Employee(experience=2.5, github_link='https://github.com/1'),
+    Employee(experience=1.5, github_link='https://github.com/2')
+]
+company_developers_list = get_employee_list(employees=company_developers)
+
+## create list objects of managers
+company_managers = [
+    Employee(experience=4.5, github_link='https://github.com/3'),
+    Employee(experience=5.7, github_link='https://github.com/4')
+]
+company_managers_list = get_employee_list(employees=company_managers)
+```
+
+
 
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