Python AST Viewer

The Python AST Viewer parses your code into its Abstract Syntax Tree and displays the node hierarchy the interpreter actually works with. It's built for developers learning compiler and language internals, and for anyone building Python tooling — linters, formatters, code-mods, static analyzers, or obfuscators — where reading and transforming the AST is the core technique.

When Python runs your code, it first tokenizes the source, then parses those tokens into an AST: a tree in which every construct — a module, function definition, loop, if-statement, function call, or literal — becomes a typed node with named fields and child nodes. This tree is the structured, unambiguous form of your program, which is why real tooling operates on it instead of manipulating raw text with regular expressions.

Seeing the tree makes abstract behavior concrete. You can watch how operator precedence nests a BinOp, how a list comprehension expands into its component nodes, how default arguments and decorators attach to a FunctionDef, or how an assignment splits into targets and a value. It's one of the fastest ways to build an accurate mental model of Python's grammar.

The same structure is available in Python itself through the built-in ast module: ast.parse(source) returns the tree, ast.dump() prints it, ast.walk() and ast.NodeVisitor let you traverse it, and ast.NodeTransformer lets you rewrite it. This viewer is essentially an interactive, no-setup front end to ast.parse — handy for prototyping a visitor or confirming what a snippet compiles to before you write the traversal code.

Everything runs client-side, so your code is parsed in your browser and never uploaded. Paste a snippet, expand the nodes, and explore exactly how Python sees your program.