📘Cisco DevNet Associate (200-901 DEVASC)

In real IT environments, especially in network automation and API integration, code can quickly become large and complex. If code is not properly organized, it becomes difficult to read, test, fix, and reuse.

To solve this problem, developers organize code into:

Methods / Functions
Classes
Modules

Let us understand each one clearly and in simple language.

1️⃣ Methods / Functions

What Is a Function?

A function (also called a method in some contexts) is a block of reusable code that performs a specific task.

Instead of writing the same code again and again, you write it once inside a function and call it whenever needed.

Simple Structure (Python example)

def get_device_status():
    print("Checking device status...")

You can then call it like this:

get_device_status()

Benefits of Using Functions

1. Code Reusability

In IT environments, you often repeat tasks such as:

Sending API requests
Authenticating to a controller
Parsing JSON responses
Logging output

Instead of rewriting the same code multiple times, you create a function.

Example:

A function that sends an HTTP GET request to a network controller.
You reuse it whenever you need data from different endpoints.

This reduces duplication and saves time.

2. Better Readability

Large scripts become hard to understand if everything is written in one block.

Compare this:

❌ Bad practice:

# 300 lines of continuous code

✅ Good practice:

authenticate()
get_devices()
check_status()
generate_report()

Now the code reads like a sequence of steps. Even non-developers can understand what the program is doing.

3. Easier Testing

In DevNet, automation scripts must be tested.

If functionality is inside functions:

You can test each function independently.
You can isolate bugs quickly.

Example:
If API authentication fails, you only check the authenticate() function.

4. Easier Debugging

When something fails:

You know which function caused the issue.
You don’t have to search through the entire script.

5. Better Maintenance

If the API endpoint changes:

You modify only the function.
All calls to that function automatically use the updated logic.

2️⃣ Classes

What Is a Class?

A class is a blueprint used to create objects. It groups:

Data (variables)
Behavior (functions/methods)

Together in one structure.

Classes are used in Object-Oriented Programming (OOP).

Why Classes Are Important in DevNet

In real IT environments, we often represent:

Network devices
Users
API clients
Configurations
Sessions

Each of these has:

Properties (IP address, hostname, token)
Actions (connect, disconnect, configure)

A class helps organize these together.

Example (Network Device Class)

class NetworkDevice:
    def __init__(self, ip, username, password):
        self.ip = ip
        self.username = username
        self.password = password

    def connect(self):
        print("Connecting to device...")

    def get_config(self):
        print("Getting configuration...")

Now we can create multiple devices:

device1 = NetworkDevice("10.1.1.1", "admin", "pass")
device2 = NetworkDevice("10.1.1.2", "admin", "pass")

Benefits of Using Classes

1. Logical Organization

Classes group related data and functions together.

Instead of:

Separate variables for IP, username, password
Separate functions that use them

Everything is organized inside one structure.

2. Scalability

In automation projects:

You may manage 500+ devices.
You may interact with multiple APIs.

Classes make it easier to scale your solution without rewriting code.

3. Reusability

You can reuse the class in multiple scripts or projects.

Example:

A class that handles REST API authentication can be reused in:
- Device inventory scripts
- Monitoring tools
- Configuration automation scripts

4. Security Improvement

Sensitive data (like tokens) can be stored inside objects rather than global variables.

This reduces accidental exposure.

5. Better Abstraction

Users of the class do not need to understand internal implementation.

Example:

device.connect()

The user doesn’t need to know:

Whether it uses SSH
Whether it uses REST API
How authentication works internally

This simplifies usage.

3️⃣ Modules

What Is a Module?

A module is a file that contains:

Functions
Classes
Variables

Modules allow you to split a large program into multiple files.

Example:

main.py
network.py
authentication.py
utils.py

Each file is a module.

Why Modules Are Critical in DevNet

Automation scripts grow very quickly.

Example project:

API handling
Logging
Error handling
Configuration management
Reporting

If everything is in one file:

It becomes unmanageable.

Modules solve this problem.

Benefits of Using Modules

1. Better Code Organization

You can separate code by responsibility:

api_client.py → handles REST calls
device.py → contains device class
config.py → configuration settings
utils.py → helper functions

This follows the separation of concerns principle.

2. Reusability Across Projects

You can import modules into other scripts:

from api_client import authenticate

Now multiple automation projects can reuse the same module.

3. Easier Team Collaboration

In enterprise IT environments:

One developer works on API integration.
Another works on logging.
Another handles reporting.

Modules allow teams to work independently without conflicts.

4. Easier Testing

You can test each module separately.

This is important in DevOps and CI/CD pipelines.

5. Cleaner Main Program

Instead of 1000 lines in one file:

import api
import device
import report

api.authenticate()
device.get_status()
report.generate()

This is clean and professional.

Comparison: Functions vs Classes vs Modules

Feature	Functions	Classes	Modules
Purpose	Perform a task	Represent an object	Organize code into files
Reusability	Yes	Yes	Yes
Encapsulation	Limited	Strong	Medium
Best for	Small reusable logic	Complex structured systems	Large projects

How This Applies to DevNet Exam Topics

For 200-901 DEVASC, this topic connects to:

Python programming fundamentals
Writing automation scripts
API integrations
REST API handling
Network automation tools
Software development best practices

You may see exam questions like:

Why use functions instead of repeating code?
What is the benefit of object-oriented programming?
Why divide code into modules?
What makes code maintainable and scalable?

You must understand:

Modularity
Reusability
Maintainability
Scalability
Readability
Testability

Real IT Example (Network Automation Context)

Imagine an automation system that:

Authenticates to Cisco DNA Center
Retrieves device inventory
Checks device health
Pushes configurations
Generates a report

Without structure:

One long file
Repeated code
Hard to debug

With proper organization:

Functions:

authenticate()
get_inventory()
push_config()

Class:

DNACenterAPI

Modules:

api.py
devices.py
reporting.py
main.py

This is how professional automation projects are built.

Key Exam Points to Remember

✅ Functions:

Improve readability
Reduce duplication
Make debugging easier
Improve maintainability

✅ Classes:

Support object-oriented programming
Group data and behavior
Improve scalability
Enable abstraction and encapsulation

✅ Modules:

Split large programs into files
Improve organization
Support teamwork
Promote code reuse

Final Summary (Very Important for Exam)

Organizing code into functions, classes, and modules:

Makes code easier to read
Makes code easier to test
Makes code easier to debug
Improves scalability
Reduces duplication
Supports team development
Follows professional software development practices

For the Cisco DevNet Associate (200-901 DEVASC) exam, always remember:

Well-organized code is maintainable, reusable, scalable, and easier to automate in real IT environments.