Python Security: Best Practices for Developers

September 21, 2023
5 mins
Learn best practices for secure Python development, explore how Safety ensures your Python code's dependencies are safe, and discover tips for integrating security into your development workflow.


In today's rapidly evolving technological landscape, the importance of security in Python applications cannot be overstated. As developers, it's essential to adhere to best practices to protect our applications from threats. This article will provide a concise overview of Python security best practices, with a focus on practical steps and powerful tools to enhance your coding skills and application security.

Input Validation

User input can be a breeding ground for security vulnerabilities. Ensure that you validate and sanitize all input to prevent malicious data from wreaking havoc in your code. Use Python's built-in functions like str.isalnum() and libraries such as validators for this purpose.

Input sanitization involves validating, encoding, and filtering data to prevent malicious inputs from causing harm to your application. In Python, some techniques include using string methods to escape characters, restricting input length, and employing regular expressions for input validation.

Tips and Techniques

  • Always validate user input against a whitelist of acceptable values to prevent injection attacks.
  • Implement input length limits to prevent buffer overflows and excessive resource usage.
  • Employ regular expressions for strict input validation.
  • Encode data when passing it between components to prevent cross-site scripting (XSS) attacks.

Static Code Analysis

Regularly scanning your code for vulnerabilities is an effective way to secure your Python projects.

Code Scanning Tools

Several popular tools facilitate code scanning and linting, such as Bandit, PyLint, and Flake8. These tools not only detect security vulnerabilities but also ensure code quality by identifying potential issues during development.

How to Scan Code Effectively

  • Integrate security scanning into your CI/CD pipeline to ensure automated regular checks.
  • Review security scan results, prioritize discovered vulnerabilities, and apply patches as needed.
  • Update linting rules and configurations regularly to cover emerging threats.

Dependency Security

Managing the dependencies within your Python applications is crucial to maintain security as software-supply-chain attacks continue to grow into one of the main vectors of attack.

Checking for Dependency Vulnerabilities and Malicious Packages

  • Many free tools like GitHub and GitLab include basic security scanning for Python projects based on open-source vulnerability data.
  • For startups, commercial teams and enterprises who need commercial-level security, Safety CLI can be used on developer machines to scan individual requirements files or perform system-wide scans on developer machines, CI/CD pipelines, and production systems to detect vulnerable and malicious dependencies.
  • Developers and DevSecOps are alerted to the presence of vulnerabilities in Safety Platform and in Safety CLI, complete with fix recommendations to minimize the effort required to remove vulnerabilities from your software supply chain.
  • Safety CLI utilizes up-to-date vulnerability data from the industry’s most comprehensive database of vulnerabilities and malicious packages, alerting teams to new risks and attack vectors as they emerge.

Downloading and Installing Packages Safely

  • Only download packages from trusted sources like Safety Gateway and the Python Package Index (PyPI). Verify package authenticity and avoid typosquatting attacks by double-checking spelling in your installation commands.
  • Use virtual environments to isolate dependencies and prevent conflicts.

Reviewing Dependency Licenses

  • Understand and comply with the licenses of all dependencies used in your project. Safety CLI has the ability to detect dependencies system-wide and report on license status
  • Be aware of compatibility between different licenses, especially when using multiple third-party libraries.

Common Python Security Vulnerabilities

Knowing the common security vulnerabilities in Python applications is essential to protect against them. Some of these vulnerabilities include:

  • Injection attacks (e.g., SQL, command, or code injection)
  • Cross-site scripting (XSS) attacks
  • Insecure deserialization
  • Remote code execution

Case Studies

  • Analyzing real-world security incidents and understanding how vulnerabilities were exploited can help developers avoid similar pitfalls in their projects.

Python Security Frameworks and Libraries

Several popular Python security frameworks and libraries can assist developers in implementing secure code. Examples include Cryptography, and Authlib.

Use Cases and Implementation

  • Select the most suitable security library or framework based on your project's requirements.
  • Follow best practices and guidelines provided by the chosen library or framework to ensure secure and efficient implementation.

Secure Coding Practices

Writing secure Python code requires following best practices and establishing good habits.


  • Limit the use of eval(), exec(), and os.system() to minimize security risks.
  • Secure Secrets: Avoid using hardcoded secrets and store them securely instead (e.g., environment variables, secret managers).
  • Secure Password Storage: Never store passwords in plain text. Use hashing algorithms like bcrypt or Argon2, available through the bcrypt and argon2-cffi libraries, to securely store your user's passwords.
  • Least Privilege Principle: When assigning permissions, stick to the principle of least privilege. Limit access to the absolute minimum required for a user or process to perform its intended function. This way, if there's a breach, the damage is contained.
  • Error Handling: Handle exceptions carefully, as they can reveal sensitive information to attackers. Avoid displaying raw error messages to users, and instead, log the errors for internal review and return a generic error message to the user.

Test-driven Development

Adopting test-driven development (TDD) assists in catching potential security issues during the development process itself. By writing tests before implementing code, developers can minimize security vulnerabilities and improve code quality.


Security is paramount when building software to protect you, your company, and your customers from financial, reputational, and regulatory harm. With attack vectors becoming increasingly sophisticated, it is essential to get the basics outlined in this article right. 

Safety is a lightweight, developer-first suite of products intended to make applying these best practices easy. By reducing vulnerability noise by 90% and performing scans using the industry’s most comprehensive vulnerability data, Safety helps data-sensitive organizations, AI/ML teams, data scientists, and developers across the world focus on building great software and less time worrying about security. 

To learn more on these topics, check out these resources:

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