Extracting parameter name. type. and default value from Oracle PL/SQL Function with ANTLR4 in Python

Learn how to correctly extract parameter names, types, and default values from Oracle PL/SQL functions using ANTLR4 and Python, avoiding common pitfalls with parse tree contexts. --- This video is based on the question https://stackoverflow.com/q/79245922/ asked by the user 'Pro West' ( https://stackoverflow.com/u/21935028/ ) and on the answer https://stackoverflow.com/a/79246545/ provided by the user 'György Gulyás' ( https://stackoverflow.com/u/7536864/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions. Visit these links for original content and any more details, such as alternate solutions, latest updates/developments on topic, comments, revision history etc. For example, the original title of the Question was: How to get parameter name, type and default value of Oracle PLSQL function body? Also, Content (except music) licensed under CC BY-SA https://meta.stackexchange.com/help/licensing The original Question post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/by-sa/4.0/ ) license, and the original Answer post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/by-sa/4.0/ ) license. If anything seems off to you, please feel free to drop me a comment under this video. --- Introduction When parsing Oracle PL/SQL functions using ANTLR4 in Python, extracting detailed parameter information such as the name, type, and default value can be tricky. A common challenge involves navigating the parse tree context objects correctly without causing attribute errors. The Problem Given a PL/SQL function like: [[See Video to Reveal this Text or Code Snippet]] We want to extract: Parameter names (p_prod_id, p_date) Their data types (VARCHAR2, DATE) Default values (if any) However, accessing context attributes improperly in ANTLR4's Python runtime causes errors such as: [[See Video to Reveal this Text or Code Snippet]] This typically happens when the parse rule returns a list or function accessor rather than a direct child node. Understanding the Issue In ANTLR4 generated Python parsers: Context properties corresponding to parser rules are methods, not attributes. When a rule can match multiple elements (like parameters), these methods accept an optional index to access a specific element. For example, ctx.parameter_name is a method, so ctx.parameter_name.identifier() is incorrect—parameter_name() must be called to get the child node, then invoke other child methods on it. Correct Approach Modify the code to call methods correctly: [[See Video to Reveal this Text or Code Snippet]] Key points: Always call context methods: ctx.parameter_name() instead of ctx.parameter_name. Use optional index arguments to access multiple parameters, e.g., ctx.parameter_name(0), ctx.parameter_name(1). Navigate down child contexts step-by-step. Extracting Default Values Default values might be present in the parameter syntax as := default_value. To extract them: Check if the parameter context includes a default_value rule or token. Add logic to capture and parse this node similarly to how you extract name and type. Summary When parsing PL/SQL function parameters using ANTLR4 and Python: Always call context methods, don't access as attributes. Use indices to navigate multiple parameters. Step through the parse tree carefully to extract names, types, and defaults. This approach avoids common AttributeErrors and makes your parser robust and maintainable.