Welcome! Today, we are going to explore an engaging task that involves managing employee records within a company. Specifically, we will work with nested dictionaries and lists to add projects and tasks for employees and retrieve those tasks as needed. This exercise will help you understand how to manipulate nested data structures efficiently.

Let's start by discussing the methods we will implement in our EmployeeRecords class.

• add_project(self, employee_id: str, project_name: str) -> bool - this method adds a new project to an employee's list of projects. If the project already exists for that employee, the method returns False. Otherwise, it adds the project and returns True.
• add_task(self, employee_id: str, project_name: str, task: str) -> bool - this method adds a new task to a specified project for an employee. If the project does not exist for that employee, the method returns False. If the task is added successfully, it returns True.
• get_tasks(self, employee_id: str, project_name: str) -> list | None - this method retrieves all tasks for a specified project of an employee. If the project does not exist for that employee, the method returns None. Otherwise, it returns the list of tasks.

Now, let's build our EmployeeRecords class step by step, ensuring we understand each component clearly.

We'll start with the basic structure of the class and initialize our data storage.

Python
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1class EmployeeRecords:
2    def __init__(self):
3        self.records = {}
4
5# Instantiate the class to ensure it works.
6records = EmployeeRecords()

In this initial setup, we define the EmployeeRecords class and create an instance variable records that is an empty dictionary. This dictionary will be used to store employee records, where each key is an employee ID and each value is another dictionary holding projects.

Next, we'll implement the add_project method to add projects to an employee's record.

Python
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1class EmployeeRecords:
2    def __init__(self):
3        self.records = {}
4
5    def add_project(self, employee_id: str, project_name: str) -> bool:
6        if employee_id not in self.records:
7            self.records[employee_id] = {}
8        if project_name in self.records[employee_id]:
9            return False
10        else:
11            self.records[employee_id][project_name] = []
12            return True
13
14# Example usage and testing
15records = EmployeeRecords()
16print(records.add_project("E123", "ProjectA"))  # Returns True
17print(records.add_project("E123", "ProjectA"))  # Returns False

Here, the add_project method checks if the given employee_id exists in the records dictionary. If not, it initializes an empty dictionary for that employee. Then, it checks if the project_name already exists for that employee. If it does, the method returns False. Otherwise, it initializes an empty list for the project (to hold tasks) and returns True.

Now, we will implement the add_task method. This method relies on the availability of the existing project.

Python
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1class EmployeeRecords:
2    def __init__(self):
3        self.records = {}
4
5    def add_project(self, employee_id: str, project_name: str) -> bool:
6        if employee_id not in self.records:
7            self.records[employee_id] = {}
8        if project_name in self.records[employee_id]:
9            return False
10        else:
11            self.records[employee_id][project_name] = []
12            return True
13
14    def add_task(self, employee_id: str, project_name: str, task: str) -> bool:
15        if employee_id not in self.records or project_name not in self.records[employee_id]:
16            return False
17        self.records[employee_id][project_name].append(task)
18        return True
19
20# Example usage and testing
21records = EmployeeRecords()
22records.add_project("E123", "ProjectA")
23print(records.add_task("E123", "ProjectA", "Task1"))  # Returns True
24print(records.add_task("E123", "NonExistentProject", "Task3"))  # Returns False

The add_task method first checks if the employee_id exists in the records dictionary and if the specified project_name exists for that employee. If either check fails, the method returns False. Otherwise, it appends the task to the list of tasks for the specified project and returns True.

Lastly, let's implement the get_tasks method to retrieve tasks from a specified employee's project.

Python
Copy to clipboard
1class EmployeeRecords:
2    def __init__(self):
3        self.records = {}
4
5    def add_project(self, employee_id: str, project_name: str) -> bool:
6        if employee_id not in self.records:
7            self.records[employee_id] = {}
8        if project_name in self.records[employee_id]:
9            return False
10        else:
11            self.records[employee_id][project_name] = []
12            return True
13
14    def add_task(self, employee_id: str, project_name: str, task: str) -> bool:
15        if employee_id not in self.records or project_name not in self.records[employee_id]:
16            return False
17        self.records[employee_id][project_name].append(task)
18        return True
19
20    def get_tasks(self, employee_id: str, project_name: str) -> list | None:
21        if employee_id not in self.records or project_name not in self.records[employee_id]:
22            return None
23        return self.records[employee_id][project_name]
24
25# Example usage and testing
26records = EmployeeRecords()
27records.add_project("E123", "ProjectA")
28records.add_task("E123", "ProjectA", "Task1")
29print(records.get_tasks("E123", "ProjectA"))  # Returns ["Task1"]
30print(records.get_tasks("E123", "NonExistentProject"))  # Returns None

The get_tasks method checks if the employee_id exists in the records dictionary and if the specified project_name exists for that employee. If either check fails, the method returns None. Otherwise, it returns the list of tasks for the specified project.

In this lesson, we successfully implemented the EmployeeRecords class for managing projects and tasks for employees using nested dictionaries and lists. We covered methods for adding projects, adding tasks to those projects, and retrieving tasks from those projects.

Understanding how to work with nested data structures allows you to efficiently manage complex data hierarchies, which improves your programming skills and problem-solving abilities. I encourage you to practice similar challenges to reinforce what you learned today.

Keep coding and exploring new challenges!