(memo) flag in the grammar file) are memoized. To improve backtracking performance, some rules (chosen by applying a Typedef struct _stmt * stmt_ty struct _stmt The statement definitions above generate the following C structure type:
Represented as a single AST node and not as a sequence of nodes as withĪll three kinds also have an ‘attributes’ argument this is shown by theįact that ‘attributes’ lacks a ‘|’ before it. Stmt arguments for body, and zero or more expr arguments forĭo notice that something like ‘arguments’, which is a node type, is Takes an identifier for the name, arguments for args, zero or more Value for the argument and it is required. Means it is optional, * means 0 or more, while no modifier means only one Modifiers on the argument type specify the number of values needed ? They all take arguments of various kinds and amounts. The preceding example describes two different kinds of statements and anĮxpression: function definitions, return statements, and yield expressions.Īll three kinds are considered of type stmt as shown by | separating | Return(expr? value) | Yield(expr? value) Stmt = FunctionDef(identifier name, arguments args, stmt* body, The following fragment of the Python ASDL construct demonstrates the The definition is independent of its realization in any Particular source construct, such as an ‘if’ statement or an attribute Most definitions in the AST correspond to a Specialized types, like list comprehensions and exception handlers) isĭefined by the ASDL. The definition of the AST nodes for Python is found in the fileĮach AST node (representing statements, expressions, and several Specification of the AST nodes is specified using the Zephyr Abstract It can be thought of as an abstract representation of the source code.
Program structure without the necessity of containing the source code The abstract syntax tree (AST) is a high-level representation of the See also Green Tree Snakes - the missing Python AST docs by Thomas Kluyver. Various C files, including Parser/parser.c are generated from (such as :, numbers, etc.) can be found in Grammar/Tokens. The grammar file for Python can be found in Stream of characters as is more common with PEG parsers). Unusual design (since its input is a stream of tokens rather than a Parsing ¶Īs of Python 3.9, Python’s parser is a PEG parser of a somewhat To read some source to have an exact understanding of all details. In terms of the how the entire system works. To explain what is needed for compilation. This document does not touch on how parsing works beyond what is needed The purpose of this document is to outline how these steps of the process work. Transform AST into a Control Flow Graph ( Python/compile.c)Įmit bytecode based on the Control Flow Graph ( Python/compile.c) Parse the stream of tokens into an Abstract Syntax Tree ( Parser/parser.c) Tokenize the source code ( Parser/tokenizer.c)
In CPython, the compilation from source code to bytecode involves several steps: Toggle table of contents sidebar Design of CPython’s Compiler ¶ Abstract ¶