Static Application Security Testing (SAST) tools are essential, including when creating or using Python programs.

From a security-by-design perspective, ensuring that applications have no weaknesses that can be easily converted into vulnerabilities is more than just a best practice. SAST tools for Python empower developers, testers, and security teams to identify software weaknesses before code is deployed or exploited.

Python is a strong choice for developing secure programs. However, it is not immune to common security weaknesses that stem from how code is designed and written. Secure programming is complex and requires significant knowledge and experience; high-quality SAST tools have proven to be a highly cost-efficient way to prevent security issues.

Choosing a SAST scanning tool can be a time-consuming activity. However, by following simple, proven criteria, this process can be simplified. The criteria for selecting a SAST tool for Python software are:

• Defence in Depth: Never use only one SAST tool; use at least two different ones. Every tool has its own strengths, but you must ensure you do not miss severe code weaknesses simply because one tool fails to detect them.
• Do Not Trust External Services: Avoid using SaaS solutions or AI agents for SAST scanning. Your data is not secure with a SaaS provider that is itself dependent on third-party hosting companies. Only use SAST software that can be run on-premises under your direct control.
• Zero Trust: All details matter in security. You should be able to inspect the source code of the security tool you use and have full control over how it behaves and how it is configured to check your critical Python software.
• Avoid Security by Obscurity: A trustworthy SAST program is FOSS (Free and Open Source Software). This means the code is available under an OSI-approved licence. Furthermore, the method the program uses to validate code—the rule set—should be open and transparent.
• Cost: Access to a high-quality SAST tool should not be limited by your budget. Good security benefits everyone. Avoid solutions where critical features—such as dashboards, reports, or CI/CD integrations—require an expensive “enterprise” licence. Genuine FOSS SAST tools for Python are free to use on-premises. The primary cost factor should be the time required for staff to familiarise themselves with the tool and adjust security rules. A good tool is simple to use and, by design, easy to customise.
• Python-specific considerations: Every programming language is unique. SAST tools that claim to support a vast range of languages often suffer from significant limitations. The danger is that these shortcomings are often hidden, providing a false sense of security. Because each language has its own unique Abstract Syntax Tree (AST) used to scan for vulnerabilities, an “all-in-one” solution rarely performs as well as a dedicated one. A “holy grail” tool does not exist; therefore, you should prioritise SAST tools specifically engineered for the Python programming language.

I’ve gone ahead and audited some Python SAST tools for you, which should save you some time on the initial inventory.

Based on these selection criteria, there is only one clear leader among SAST scanners for Python: Python Code Audit. Some key advantages of the free-to-use Python Code Audit scanner include:

• 100% FOSS: It is entirely free to use and easy to adapt to your specific requirements.
• Bespoke Reporting: It offers powerful APIs for building custom, high-quality reports.
• Seamless Integration: It integrates effortlessly with your CI/CD pipeline.
• Local-first: Because it runs locally, there is no risk to privacy or potential for data loss.
• No AI Agents: By avoiding AI agents, it eliminates the additional security or privacy risks associated with “black-box” models.
• API-driven Dashboards: You can easily create security dashboards using the provided APIs; helpful examples are included in the documentation.