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diff --git a/Doc/library/_ast.rst b/Doc/library/_ast.rst deleted file mode 100644 index cb7e44e..0000000 --- a/Doc/library/_ast.rst +++ /dev/null @@ -1,83 +0,0 @@ -.. _ast: - -Abstract Syntax Trees -===================== - -.. module:: _ast - :synopsis: Abstract Syntax Tree classes. - -.. sectionauthor:: Martin v. Löwis <martin@v.loewis.de> - - -The ``_ast`` module helps Python applications to process trees of the Python -abstract syntax grammar. The abstract syntax itself might change with each -Python release; this module helps to find out programmatically what the current -grammar looks like. - -An abstract syntax tree can be generated by passing :data:`_ast.PyCF_ONLY_AST` -as a flag to the :func:`compile` builtin function. The result will be a tree of -objects whose classes all inherit from :class:`_ast.AST`. - -A modified abstract syntax tree can be compiled into a Python code object using -the built-in :func:`compile` function. - -The actual classes are derived from the ``Parser/Python.asdl`` file, which is -reproduced below. There is one class defined for each left-hand side symbol in -the abstract grammar (for example, ``_ast.stmt`` or ``_ast.expr``). In addition, -there is one class defined for each constructor on the right-hand side; these -classes inherit from the classes for the left-hand side trees. For example, -``_ast.BinOp`` inherits from ``_ast.expr``. For production rules with -alternatives (aka "sums"), the left-hand side class is abstract: only instances -of specific constructor nodes are ever created. - -Each concrete class has an attribute ``_fields`` which gives the names of all -child nodes. - -Each instance of a concrete class has one attribute for each child node, of the -type as defined in the grammar. For example, ``_ast.BinOp`` instances have an -attribute ``left`` of type ``_ast.expr``. Instances of ``_ast.expr`` and -``_ast.stmt`` subclasses also have lineno and col_offset attributes. The lineno -is the line number of source text (1 indexed so the first line is line 1) and -the col_offset is the utf8 byte offset of the first token that generated the -node. The utf8 offset is recorded because the parser uses utf8 internally. - -If these attributes are marked as optional in the grammar (using a question -mark), the value might be ``None``. If the attributes can have zero-or-more -values (marked with an asterisk), the values are represented as Python lists. -All possible attributes must be present and have valid values when compiling an -AST with :func:`compile`. - -The constructor of a class ``_ast.T`` parses their arguments as follows: - -* If there are positional arguments, there must be as many as there are items in - ``T._fields``; they will be assigned as attributes of these names. -* If there are keyword arguments, they will set the attributes of the same names - to the given values. - -For example, to create and populate a ``UnaryOp`` node, you could use :: - - node = _ast.UnaryOp() - node.op = _ast.USub() - node.operand = _ast.Num() - node.operand.n = 5 - node.operand.lineno = 0 - node.operand.col_offset = 0 - node.lineno = 0 - node.col_offset = 0 - -or the more compact :: - - node = _ast.UnaryOp(_ast.USub(), _ast.Num(5, lineno=0, col_offset=0), - lineno=0, col_offset=0) - - - -Abstract Grammar ----------------- - -The module defines a string constant ``__version__`` which is the decimal -subversion revision number of the file shown below. - -The abstract grammar is currently defined as follows: - -.. literalinclude:: ../../Parser/Python.asdl |