pylint - Check python code for errors - Stack Overflow
How to check python code's syntax error before running it - Stack Overflow
compilation - How to check syntax of Python file/script without executing it? - Stack Overflow
Are there any good syntax or style checkers recommended?
What is a syntax error in Python?
A Python syntax error is an issue that occurs when Python code is interpreted during execution. Syntax errors are one of three basic types of error, and are almost always fatal because the Python interpreter cannot understand a line of code. Logic errors occur when the code is valid, but the application doesn’t do what the developer intended. Exceptions occur when the Python parser understands a line of code, but the interpreter is unable to execute it during runtime.
Why use Snyk's Python Code Checker?
What does it do? Snyk’s Python Code Checker (Snyk Code) is an AI-powered SAST tool that analyzes Python code for security issues and bugs, delivering real-time feedback within your IDE.
What types of issues are detected? It finds a broad spectrum of bugs (e.g., file I/O corruption, API misuse, null dereference, threading deadlocks, regex DoS, resource leaks) and vulnerabilities (e.g., code injection, SQL injection, weak cryptography, information disclosure).
How is AI implemented? The tool leverages a human-in-the-loop AI model—combining expert-curated rules with advanced ML for semantic, data-flow, and structural code analysis.
Integration capabilities? It integrates seamlessly with your workflow—providing real-time scanning in IDEs and CI/CD, plus PR scanning to enforce security before code merges.
What analysis methods are applied? It applies configuration, semantic, data-flow, and structural analyses to deeply understand code behavior and context.
Why use an AI-powered checker like this? AI enables earlier detection of sophisticated bugs and vulnerabilities that ordinary linters miss—reducing false positives and improving developer efficiency.
Does it support Python dependency scanning? Yes—while Snyk Code focuses on code logic, Snyk Open Source handles dependency scanning, offering comprehensive Python security.
How actionable is the feedback? Snyk delivers developer-friendly, inline remediation guidance, making it easy to fix issues efficiently.
What are common Python syntax and logical errors?
There are a variety of syntax and logical errors, so it’s important to know how to remediate the most common issues that a debugger or code checker may flag. While logical errors aren’t recognized by the Python interpreter, they still prevent the application from performing as the developer originally intended. Here are some tips to avoid some common logical flaws when writing Python code:
Remember to invoke a function to start the execution of the program.
Check for infinite loops where the program gets stuck in a recurring code block.
Use print statements to understand the flow of execution and ensure it’s correct.
Avoid complex expressions that make code harder to read and debug.
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It's not a syntax error. b=c is perfectly valid syntax, whether or not c exists. In fact, some other module could have done
import __builtin__
__builtin__.c = 3
in which case there would be a built-in c variable with value 3 available to all modules, and your code would run fine.
For a somewhat less pathological example, if the file contains a * import such as
from numpy import *
the import will dump a whole bunch of names into the module's global namespace, and there's no way to tell what those names are. Even without import *, though, Python can't be sure that a reference to an unknown name is an error at compile time.
If you want to detect semantic errors such as this, you'll need a more complex analysis of the program. Integrating with an existing linter like pylint, as suggested by NPE, is likely to be more productive than writing your own tool. If you really want to do it yourself, you can parse the code with ast.parse and examine the AST, going statement by statement to see what variables exist at what points. You'll still never catch all bugs, but you'll find quite a few.
It's a tricky one, for many reasons.
It might not be a bad idea to try and integrate with pylint instead of trying to come up with your own.