One of the best things about open source software is the ability to reuse other people's code. Repurposing code helps you save time, discover new functionality, and learn other programming styles. There are two main ways to reuse code:
- Copying and pasting a code snippet directly into your project. If you're new to coding, this is the quickest way to start reusing code.
- Importing a library into your project. While this approach takes some time to learn, it's ultimately easier and more efficient. It's also a foundational skill for software development.
Using other people's code snippets in your project
As you are learning to code, you might copy and paste other people's code snippets into your project. While using code snippets is a great way to learn to code and save time, there are a few key steps you should always take before copying another developer's code.
1. Finding and understanding a code snippet
Your first step is to choose a code snippet you want to reuse. To find eligible code, try searching GitHub. You can narrow your search with search qualifiers like language:YOUR-SEARCH-LANGUAGE.
For example, let's say you want to reuse Python code that calculates the factorial of a number. By searching GitHub for factorial language:python is:repository, we find the new2code/python-factorial repository, which implements the calculator in factorial_finder.py using a loop:
# Initialize the factorial result to 1
factorial = 1
# Initialize the input number to 6
number = 6
# Loop from 1 to number (inclusive) and multiply factorial by each number
for i in range(1, number + 1):
factorial *= i
print(f"The factorial of {number} is {factorial}")
If you don't immediately understand a code snippet, you can ask Copilot to explain it. In the menu bar at the top of the factorial_finder.py file, click to start a conversation about the file, then ask Copilot to Explain this program.
2. Understanding project licensing
Before you can reuse the code you've found, you need to understand its licensing. Licenses determine how you can use the code in a project, including your ability to copy, modify, and distribute that code.
You can find the license for a project in the "About" section of the main page of the repository. For example, we can see that the new2code/python-factorial repository is licensed under the MIT license. To read the license, click MIT license.
Note
If the code you want to use is under a different license, use the license summaries in Licenses to understand it.
We want to copy the entire factorial_finder.py file, so the MIT license indicates that we should include a copy of the license in our own project. At the top of your Python file, paste the license as a comment.
3. Using and modifying code snippets
Now that you understand the code and its licensing, you can paste the code snippet into your project. While you may be able to use the code as is, you'll often need to modify it for your specific use case.
For our factorial example, let's say we want to quickly calculate the factorials of 5, 7, 9, and 10. Instead of copying and pasting the entire program for each number, we can move our calculator into a function that takes a number as an argument.
To help us make these changes, let's ask Copilot to suggest and explain an implementation. We can paste our current code into the chat window, then prompt Copilot to Wrap the Python code above in a function. Copilot will generate code that looks something like this:
def calculate_factorial(number):
# Initialize the factorial result to 1
factorial = 1
# Loop from 1 to number (inclusive) and multiply factorial by each number
for i in range(1, number + 1):
factorial *= i
return factorial
def calculate_factorial(number):
# Initialize the factorial result to 1
factorial = 1
# Loop from 1 to number (inclusive) and multiply factorial by each number
for i in range(1, number + 1):
factorial *= i
return factorial
With our new function, we can easily find the factorials of our numbers by adding the following code to our project, then running the Python program:
print(calculate_factorial(5)) print(calculate_factorial(7)) print(calculate_factorial(9)) print(calculate_factorial(10))
print(calculate_factorial(5))
print(calculate_factorial(7))
print(calculate_factorial(9))
print(calculate_factorial(10))
Congratulations! You've successfully found, understood, and modified an example code snippet.
Using code from libraries in your project
Using libraries is standard practice for developers. Libraries are essentially collections of code written by other developers to perform specific tasks. You can import libraries into your project to use the pre-written code, saving you time and effort.
In this section, we'll continue working with the Python factorial calculator example from the previous section. For reference, here's our current code:
def calculate_factorial(number):
# Initialize the factorial result to 1
factorial = 1
# Loop from 1 to number (inclusive) and multiply factorial by each number
for i in range(1, number + 1):
factorial *= i
return factorial
print(calculate_factorial(5))
print(calculate_factorial(7))
print(calculate_factorial(9))
print(calculate_factorial(10))
def calculate_factorial(number):
# Initialize the factorial result to 1
factorial = 1
# Loop from 1 to number (inclusive) and multiply factorial by each number
for i in range(1, number + 1):
factorial *= i
return factorial
print(calculate_factorial(5))
print(calculate_factorial(7))
print(calculate_factorial(9))
print(calculate_factorial(10))
1. Finding a library
Once you know what functionality you want to add to your project, you can search for a library with relevant code. Copilot Chat is an easy way to search for libraries, since you can use natural language to describe exactly what you're looking for.
Returning to our factorial calculator, finding a factorial is a pretty common function, and there's a good chance someone included that function in an existing library. If we ask Copilot Is there a Python library with a function for calculating a factorial?, Copilot will tell us a factorial function is included in the math module from the standard Python library.
2. Prioritizing security in your project
When you add a library or module to your project, you create what's called a dependency. Dependencies are pre-written code bundles that your project relies on to function correctly, and if they aren't carefully written or maintained, they can introduce security vulnerabilities to your work. Thankfully, there are some steps you can take to best protect your project.
Using popular libraries
Popular libraries are more likely to be secure because they are actively maintained and used by many developers. One good marker of popularity is the number of stars a repository has. If you can't find the GitHub repository for a dependency, try asking Copilot for help.
For example, for the math module, we can prompt Copilot to Find the GitHub repository containing the code for the math module in Python. Copilot will tell us that the math module is defined in python/cpython, which has over 64,000 stars.
Enabling Dependabot alerts for your project
If enabled, Dependabot alerts are automatically generated when Dependabot detects a security issue in your dependencies, helping you quickly fix vulnerabilities. Dependabot is available for free on all open source GitHub repositories.
To turn Dependabot alerts on, click the Security tab for your project's GitHub repository. Next to Dependabot alerts, click Enable Dependabot alerts. You can access Dependabot alerts from the Dependabot tab of the sidebar.
3. Implementing code from a library
Now that you have taken steps to secure your work, you need to import the library into your project, then use its contents in your code. You can read the documentation for the library to learn how to do it yourself, or you can ask Copilot to suggest and explain an implementation for you.
For our factorial program, we can ask Copilot something like How do I use the factorial function of the math module in my Python project? Copilot will then suggest a version of the following code:
import math
# Calculate the factorial of a number
number = 5
result = math.factorial(number)
print(f"The factorial of {number} is {result}")
import math
# Calculate the factorial of a number
number = 5
result = math.factorial(number)
print(f"The factorial of {number} is {result}")
After you replace the existing code in your project with the above implementation, you've successfully reused code from a library in your example project!