693 lines
30 KiB
ReStructuredText
693 lines
30 KiB
ReStructuredText
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:mod:`parser` --- Access Python parse trees
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===========================================
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.. module:: parser
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:synopsis: Access parse trees for Python source code.
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.. moduleauthor:: Fred L. Drake, Jr. <fdrake@acm.org>
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.. sectionauthor:: Fred L. Drake, Jr. <fdrake@acm.org>
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.. Copyright 1995 Virginia Polytechnic Institute and State University and Fred
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L. Drake, Jr. This copyright notice must be distributed on all copies, but
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this document otherwise may be distributed as part of the Python
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distribution. No fee may be charged for this document in any representation,
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either on paper or electronically. This restriction does not affect other
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elements in a distributed package in any way.
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.. index:: single: parsing; Python source code
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The :mod:`parser` module provides an interface to Python's internal parser and
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byte-code compiler. The primary purpose for this interface is to allow Python
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code to edit the parse tree of a Python expression and create executable code
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from this. This is better than trying to parse and modify an arbitrary Python
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code fragment as a string because parsing is performed in a manner identical to
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the code forming the application. It is also faster.
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.. note::
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From Python 2.5 onward, it's much more convenient to cut in at the Abstract
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Syntax Tree (AST) generation and compilation stage, using the :mod:`ast`
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module.
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The :mod:`parser` module exports the names documented here also with "st"
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replaced by "ast"; this is a legacy from the time when there was no other
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AST and has nothing to do with the AST found in Python 2.5. This is also the
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reason for the functions' keyword arguments being called *ast*, not *st*.
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The "ast" functions will be removed in Python 3.0.
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There are a few things to note about this module which are important to making
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use of the data structures created. This is not a tutorial on editing the parse
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trees for Python code, but some examples of using the :mod:`parser` module are
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presented.
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Most importantly, a good understanding of the Python grammar processed by the
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internal parser is required. For full information on the language syntax, refer
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to :ref:`reference-index`. The parser
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itself is created from a grammar specification defined in the file
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:file:`Grammar/Grammar` in the standard Python distribution. The parse trees
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stored in the ST objects created by this module are the actual output from the
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internal parser when created by the :func:`expr` or :func:`suite` functions,
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described below. The ST objects created by :func:`sequence2st` faithfully
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simulate those structures. Be aware that the values of the sequences which are
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considered "correct" will vary from one version of Python to another as the
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formal grammar for the language is revised. However, transporting code from one
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Python version to another as source text will always allow correct parse trees
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to be created in the target version, with the only restriction being that
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migrating to an older version of the interpreter will not support more recent
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language constructs. The parse trees are not typically compatible from one
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version to another, whereas source code has always been forward-compatible.
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Each element of the sequences returned by :func:`st2list` or :func:`st2tuple`
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has a simple form. Sequences representing non-terminal elements in the grammar
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always have a length greater than one. The first element is an integer which
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identifies a production in the grammar. These integers are given symbolic names
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in the C header file :file:`Include/graminit.h` and the Python module
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:mod:`symbol`. Each additional element of the sequence represents a component
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of the production as recognized in the input string: these are always sequences
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which have the same form as the parent. An important aspect of this structure
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which should be noted is that keywords used to identify the parent node type,
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such as the keyword :keyword:`if` in an :const:`if_stmt`, are included in the
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node tree without any special treatment. For example, the :keyword:`if` keyword
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is represented by the tuple ``(1, 'if')``, where ``1`` is the numeric value
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associated with all :const:`NAME` tokens, including variable and function names
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defined by the user. In an alternate form returned when line number information
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is requested, the same token might be represented as ``(1, 'if', 12)``, where
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the ``12`` represents the line number at which the terminal symbol was found.
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Terminal elements are represented in much the same way, but without any child
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elements and the addition of the source text which was identified. The example
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of the :keyword:`if` keyword above is representative. The various types of
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terminal symbols are defined in the C header file :file:`Include/token.h` and
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the Python module :mod:`token`.
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The ST objects are not required to support the functionality of this module,
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but are provided for three purposes: to allow an application to amortize the
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cost of processing complex parse trees, to provide a parse tree representation
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which conserves memory space when compared to the Python list or tuple
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representation, and to ease the creation of additional modules in C which
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manipulate parse trees. A simple "wrapper" class may be created in Python to
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hide the use of ST objects.
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The :mod:`parser` module defines functions for a few distinct purposes. The
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most important purposes are to create ST objects and to convert ST objects to
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other representations such as parse trees and compiled code objects, but there
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are also functions which serve to query the type of parse tree represented by an
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ST object.
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.. seealso::
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Module :mod:`symbol`
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Useful constants representing internal nodes of the parse tree.
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Module :mod:`token`
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Useful constants representing leaf nodes of the parse tree and functions for
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testing node values.
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.. _creating-sts:
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Creating ST Objects
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-------------------
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ST objects may be created from source code or from a parse tree. When creating
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an ST object from source, different functions are used to create the ``'eval'``
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and ``'exec'`` forms.
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.. function:: expr(source)
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The :func:`expr` function parses the parameter *source* as if it were an input
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to ``compile(source, 'file.py', 'eval')``. If the parse succeeds, an ST object
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is created to hold the internal parse tree representation, otherwise an
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appropriate exception is thrown.
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.. function:: suite(source)
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The :func:`suite` function parses the parameter *source* as if it were an input
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to ``compile(source, 'file.py', 'exec')``. If the parse succeeds, an ST object
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is created to hold the internal parse tree representation, otherwise an
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appropriate exception is thrown.
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.. function:: sequence2st(sequence)
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This function accepts a parse tree represented as a sequence and builds an
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internal representation if possible. If it can validate that the tree conforms
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to the Python grammar and all nodes are valid node types in the host version of
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Python, an ST object is created from the internal representation and returned
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to the called. If there is a problem creating the internal representation, or
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if the tree cannot be validated, a :exc:`ParserError` exception is thrown. An
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ST object created this way should not be assumed to compile correctly; normal
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exceptions thrown by compilation may still be initiated when the ST object is
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passed to :func:`compilest`. This may indicate problems not related to syntax
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(such as a :exc:`MemoryError` exception), but may also be due to constructs such
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as the result of parsing ``del f(0)``, which escapes the Python parser but is
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checked by the bytecode compiler.
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Sequences representing terminal tokens may be represented as either two-element
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lists of the form ``(1, 'name')`` or as three-element lists of the form ``(1,
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'name', 56)``. If the third element is present, it is assumed to be a valid
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line number. The line number may be specified for any subset of the terminal
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symbols in the input tree.
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.. function:: tuple2st(sequence)
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This is the same function as :func:`sequence2st`. This entry point is
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maintained for backward compatibility.
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.. _converting-sts:
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Converting ST Objects
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---------------------
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ST objects, regardless of the input used to create them, may be converted to
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parse trees represented as list- or tuple- trees, or may be compiled into
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executable code objects. Parse trees may be extracted with or without line
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numbering information.
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.. function:: st2list(ast[, line_info])
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This function accepts an ST object from the caller in *ast* and returns a
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Python list representing the equivalent parse tree. The resulting list
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representation can be used for inspection or the creation of a new parse tree in
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list form. This function does not fail so long as memory is available to build
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the list representation. If the parse tree will only be used for inspection,
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:func:`st2tuple` should be used instead to reduce memory consumption and
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fragmentation. When the list representation is required, this function is
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significantly faster than retrieving a tuple representation and converting that
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to nested lists.
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If *line_info* is true, line number information will be included for all
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terminal tokens as a third element of the list representing the token. Note
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that the line number provided specifies the line on which the token *ends*.
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This information is omitted if the flag is false or omitted.
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.. function:: st2tuple(ast[, line_info])
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This function accepts an ST object from the caller in *ast* and returns a
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Python tuple representing the equivalent parse tree. Other than returning a
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tuple instead of a list, this function is identical to :func:`st2list`.
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If *line_info* is true, line number information will be included for all
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terminal tokens as a third element of the list representing the token. This
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information is omitted if the flag is false or omitted.
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.. function:: compilest(ast[, filename='<syntax-tree>'])
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.. index:: builtin: eval
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The Python byte compiler can be invoked on an ST object to produce code objects
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which can be used as part of an :keyword:`exec` statement or a call to the
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built-in :func:`eval` function. This function provides the interface to the
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compiler, passing the internal parse tree from *ast* to the parser, using the
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source file name specified by the *filename* parameter. The default value
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supplied for *filename* indicates that the source was an ST object.
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Compiling an ST object may result in exceptions related to compilation; an
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example would be a :exc:`SyntaxError` caused by the parse tree for ``del f(0)``:
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this statement is considered legal within the formal grammar for Python but is
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not a legal language construct. The :exc:`SyntaxError` raised for this
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condition is actually generated by the Python byte-compiler normally, which is
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why it can be raised at this point by the :mod:`parser` module. Most causes of
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compilation failure can be diagnosed programmatically by inspection of the parse
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tree.
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.. _querying-sts:
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Queries on ST Objects
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---------------------
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Two functions are provided which allow an application to determine if an ST was
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created as an expression or a suite. Neither of these functions can be used to
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determine if an ST was created from source code via :func:`expr` or
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:func:`suite` or from a parse tree via :func:`sequence2st`.
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.. function:: isexpr(ast)
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.. index:: builtin: compile
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When *ast* represents an ``'eval'`` form, this function returns true, otherwise
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it returns false. This is useful, since code objects normally cannot be queried
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for this information using existing built-in functions. Note that the code
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objects created by :func:`compilest` cannot be queried like this either, and
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are identical to those created by the built-in :func:`compile` function.
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.. function:: issuite(ast)
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This function mirrors :func:`isexpr` in that it reports whether an ST object
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represents an ``'exec'`` form, commonly known as a "suite." It is not safe to
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assume that this function is equivalent to ``not isexpr(ast)``, as additional
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syntactic fragments may be supported in the future.
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.. _st-errors:
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Exceptions and Error Handling
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-----------------------------
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The parser module defines a single exception, but may also pass other built-in
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exceptions from other portions of the Python runtime environment. See each
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function for information about the exceptions it can raise.
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.. exception:: ParserError
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Exception raised when a failure occurs within the parser module. This is
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generally produced for validation failures rather than the built in
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:exc:`SyntaxError` thrown during normal parsing. The exception argument is
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either a string describing the reason of the failure or a tuple containing a
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sequence causing the failure from a parse tree passed to :func:`sequence2st`
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and an explanatory string. Calls to :func:`sequence2st` need to be able to
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handle either type of exception, while calls to other functions in the module
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will only need to be aware of the simple string values.
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Note that the functions :func:`compilest`, :func:`expr`, and :func:`suite` may
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throw exceptions which are normally thrown by the parsing and compilation
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process. These include the built in exceptions :exc:`MemoryError`,
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:exc:`OverflowError`, :exc:`SyntaxError`, and :exc:`SystemError`. In these
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cases, these exceptions carry all the meaning normally associated with them.
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Refer to the descriptions of each function for detailed information.
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.. _st-objects:
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ST Objects
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----------
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Ordered and equality comparisons are supported between ST objects. Pickling of
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ST objects (using the :mod:`pickle` module) is also supported.
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.. data:: STType
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The type of the objects returned by :func:`expr`, :func:`suite` and
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:func:`sequence2st`.
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ST objects have the following methods:
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.. method:: ST.compile([filename])
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Same as ``compilest(st, filename)``.
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.. method:: ST.isexpr()
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Same as ``isexpr(st)``.
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.. method:: ST.issuite()
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Same as ``issuite(st)``.
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.. method:: ST.tolist([line_info])
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Same as ``st2list(st, line_info)``.
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.. method:: ST.totuple([line_info])
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Same as ``st2tuple(st, line_info)``.
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.. _st-examples:
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Examples
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--------
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.. index:: builtin: compile
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The parser modules allows operations to be performed on the parse tree of Python
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source code before the :term:`bytecode` is generated, and provides for inspection of the
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parse tree for information gathering purposes. Two examples are presented. The
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simple example demonstrates emulation of the :func:`compile` built-in function
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and the complex example shows the use of a parse tree for information discovery.
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Emulation of :func:`compile`
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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While many useful operations may take place between parsing and bytecode
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generation, the simplest operation is to do nothing. For this purpose, using
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the :mod:`parser` module to produce an intermediate data structure is equivalent
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to the code ::
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>>> code = compile('a + 5', 'file.py', 'eval')
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>>> a = 5
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>>> eval(code)
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10
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The equivalent operation using the :mod:`parser` module is somewhat longer, and
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allows the intermediate internal parse tree to be retained as an ST object::
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>>> import parser
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>>> st = parser.expr('a + 5')
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>>> code = st.compile('file.py')
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>>> a = 5
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>>> eval(code)
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10
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An application which needs both ST and code objects can package this code into
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readily available functions::
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import parser
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def load_suite(source_string):
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st = parser.suite(source_string)
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return st, st.compile()
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def load_expression(source_string):
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st = parser.expr(source_string)
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return st, st.compile()
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Information Discovery
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^^^^^^^^^^^^^^^^^^^^^
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.. index::
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single: string; documentation
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single: docstrings
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Some applications benefit from direct access to the parse tree. The remainder
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of this section demonstrates how the parse tree provides access to module
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documentation defined in docstrings without requiring that the code being
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examined be loaded into a running interpreter via :keyword:`import`. This can
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be very useful for performing analyses of untrusted code.
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Generally, the example will demonstrate how the parse tree may be traversed to
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distill interesting information. Two functions and a set of classes are
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developed which provide programmatic access to high level function and class
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definitions provided by a module. The classes extract information from the
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parse tree and provide access to the information at a useful semantic level, one
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function provides a simple low-level pattern matching capability, and the other
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function defines a high-level interface to the classes by handling file
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operations on behalf of the caller. All source files mentioned here which are
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not part of the Python installation are located in the :file:`Demo/parser/`
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directory of the distribution.
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The dynamic nature of Python allows the programmer a great deal of flexibility,
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but most modules need only a limited measure of this when defining classes,
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functions, and methods. In this example, the only definitions that will be
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considered are those which are defined in the top level of their context, e.g.,
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a function defined by a :keyword:`def` statement at column zero of a module, but
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not a function defined within a branch of an :keyword:`if` ... :keyword:`else`
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construct, though there are some good reasons for doing so in some situations.
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Nesting of definitions will be handled by the code developed in the example.
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To construct the upper-level extraction methods, we need to know what the parse
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tree structure looks like and how much of it we actually need to be concerned
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about. Python uses a moderately deep parse tree so there are a large number of
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intermediate nodes. It is important to read and understand the formal grammar
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used by Python. This is specified in the file :file:`Grammar/Grammar` in the
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distribution. Consider the simplest case of interest when searching for
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docstrings: a module consisting of a docstring and nothing else. (See file
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:file:`docstring.py`.) ::
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"""Some documentation.
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"""
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Using the interpreter to take a look at the parse tree, we find a bewildering
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mass of numbers and parentheses, with the documentation buried deep in nested
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tuples. ::
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>>> import parser
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>>> import pprint
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>>> st = parser.suite(open('docstring.py').read())
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>>> tup = st.totuple()
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>>> pprint.pprint(tup)
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(257,
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(264,
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(265,
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(266,
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(267,
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(307,
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(287,
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(288,
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(289,
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(290,
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(292,
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(293,
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(294,
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(295,
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(296,
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(297,
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(298,
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(299,
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(300, (3, '"""Some documentation.\n"""'))))))))))))))))),
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(4, ''))),
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(4, ''),
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(0, ''))
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The numbers at the first element of each node in the tree are the node types;
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they map directly to terminal and non-terminal symbols in the grammar.
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Unfortunately, they are represented as integers in the internal representation,
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and the Python structures generated do not change that. However, the
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:mod:`symbol` and :mod:`token` modules provide symbolic names for the node types
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and dictionaries which map from the integers to the symbolic names for the node
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types.
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In the output presented above, the outermost tuple contains four elements: the
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integer ``257`` and three additional tuples. Node type ``257`` has the symbolic
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name :const:`file_input`. Each of these inner tuples contains an integer as the
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first element; these integers, ``264``, ``4``, and ``0``, represent the node
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types :const:`stmt`, :const:`NEWLINE`, and :const:`ENDMARKER`, respectively.
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Note that these values may change depending on the version of Python you are
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using; consult :file:`symbol.py` and :file:`token.py` for details of the
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mapping. It should be fairly clear that the outermost node is related primarily
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to the input source rather than the contents of the file, and may be disregarded
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for the moment. The :const:`stmt` node is much more interesting. In
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particular, all docstrings are found in subtrees which are formed exactly as
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this node is formed, with the only difference being the string itself. The
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association between the docstring in a similar tree and the defined entity
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(class, function, or module) which it describes is given by the position of the
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docstring subtree within the tree defining the described structure.
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By replacing the actual docstring with something to signify a variable component
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of the tree, we allow a simple pattern matching approach to check any given
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subtree for equivalence to the general pattern for docstrings. Since the
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example demonstrates information extraction, we can safely require that the tree
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be in tuple form rather than list form, allowing a simple variable
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representation to be ``['variable_name']``. A simple recursive function can
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implement the pattern matching, returning a Boolean and a dictionary of variable
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name to value mappings. (See file :file:`example.py`.) ::
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from types import ListType, TupleType
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def match(pattern, data, vars=None):
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if vars is None:
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vars = {}
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if type(pattern) is ListType:
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vars[pattern[0]] = data
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return 1, vars
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if type(pattern) is not TupleType:
|
|
return (pattern == data), vars
|
|
if len(data) != len(pattern):
|
|
return 0, vars
|
|
for pattern, data in map(None, pattern, data):
|
|
same, vars = match(pattern, data, vars)
|
|
if not same:
|
|
break
|
|
return same, vars
|
|
|
|
Using this simple representation for syntactic variables and the symbolic node
|
|
types, the pattern for the candidate docstring subtrees becomes fairly readable.
|
|
(See file :file:`example.py`.) ::
|
|
|
|
import symbol
|
|
import token
|
|
|
|
DOCSTRING_STMT_PATTERN = (
|
|
symbol.stmt,
|
|
(symbol.simple_stmt,
|
|
(symbol.small_stmt,
|
|
(symbol.expr_stmt,
|
|
(symbol.testlist,
|
|
(symbol.test,
|
|
(symbol.and_test,
|
|
(symbol.not_test,
|
|
(symbol.comparison,
|
|
(symbol.expr,
|
|
(symbol.xor_expr,
|
|
(symbol.and_expr,
|
|
(symbol.shift_expr,
|
|
(symbol.arith_expr,
|
|
(symbol.term,
|
|
(symbol.factor,
|
|
(symbol.power,
|
|
(symbol.atom,
|
|
(token.STRING, ['docstring'])
|
|
)))))))))))))))),
|
|
(token.NEWLINE, '')
|
|
))
|
|
|
|
Using the :func:`match` function with this pattern, extracting the module
|
|
docstring from the parse tree created previously is easy::
|
|
|
|
>>> found, vars = match(DOCSTRING_STMT_PATTERN, tup[1])
|
|
>>> found
|
|
1
|
|
>>> vars
|
|
{'docstring': '"""Some documentation.\n"""'}
|
|
|
|
Once specific data can be extracted from a location where it is expected, the
|
|
question of where information can be expected needs to be answered. When
|
|
dealing with docstrings, the answer is fairly simple: the docstring is the first
|
|
:const:`stmt` node in a code block (:const:`file_input` or :const:`suite` node
|
|
types). A module consists of a single :const:`file_input` node, and class and
|
|
function definitions each contain exactly one :const:`suite` node. Classes and
|
|
functions are readily identified as subtrees of code block nodes which start
|
|
with ``(stmt, (compound_stmt, (classdef, ...`` or ``(stmt, (compound_stmt,
|
|
(funcdef, ...``. Note that these subtrees cannot be matched by :func:`match`
|
|
since it does not support multiple sibling nodes to match without regard to
|
|
number. A more elaborate matching function could be used to overcome this
|
|
limitation, but this is sufficient for the example.
|
|
|
|
Given the ability to determine whether a statement might be a docstring and
|
|
extract the actual string from the statement, some work needs to be performed to
|
|
walk the parse tree for an entire module and extract information about the names
|
|
defined in each context of the module and associate any docstrings with the
|
|
names. The code to perform this work is not complicated, but bears some
|
|
explanation.
|
|
|
|
The public interface to the classes is straightforward and should probably be
|
|
somewhat more flexible. Each "major" block of the module is described by an
|
|
object providing several methods for inquiry and a constructor which accepts at
|
|
least the subtree of the complete parse tree which it represents. The
|
|
:class:`ModuleInfo` constructor accepts an optional *name* parameter since it
|
|
cannot otherwise determine the name of the module.
|
|
|
|
The public classes include :class:`ClassInfo`, :class:`FunctionInfo`, and
|
|
:class:`ModuleInfo`. All objects provide the methods :meth:`get_name`,
|
|
:meth:`get_docstring`, :meth:`get_class_names`, and :meth:`get_class_info`. The
|
|
:class:`ClassInfo` objects support :meth:`get_method_names` and
|
|
:meth:`get_method_info` while the other classes provide
|
|
:meth:`get_function_names` and :meth:`get_function_info`.
|
|
|
|
Within each of the forms of code block that the public classes represent, most
|
|
of the required information is in the same form and is accessed in the same way,
|
|
with classes having the distinction that functions defined at the top level are
|
|
referred to as "methods." Since the difference in nomenclature reflects a real
|
|
semantic distinction from functions defined outside of a class, the
|
|
implementation needs to maintain the distinction. Hence, most of the
|
|
functionality of the public classes can be implemented in a common base class,
|
|
:class:`SuiteInfoBase`, with the accessors for function and method information
|
|
provided elsewhere. Note that there is only one class which represents function
|
|
and method information; this parallels the use of the :keyword:`def` statement
|
|
to define both types of elements.
|
|
|
|
Most of the accessor functions are declared in :class:`SuiteInfoBase` and do not
|
|
need to be overridden by subclasses. More importantly, the extraction of most
|
|
information from a parse tree is handled through a method called by the
|
|
:class:`SuiteInfoBase` constructor. The example code for most of the classes is
|
|
clear when read alongside the formal grammar, but the method which recursively
|
|
creates new information objects requires further examination. Here is the
|
|
relevant part of the :class:`SuiteInfoBase` definition from :file:`example.py`::
|
|
|
|
class SuiteInfoBase:
|
|
_docstring = ''
|
|
_name = ''
|
|
|
|
def __init__(self, tree = None):
|
|
self._class_info = {}
|
|
self._function_info = {}
|
|
if tree:
|
|
self._extract_info(tree)
|
|
|
|
def _extract_info(self, tree):
|
|
# extract docstring
|
|
if len(tree) == 2:
|
|
found, vars = match(DOCSTRING_STMT_PATTERN[1], tree[1])
|
|
else:
|
|
found, vars = match(DOCSTRING_STMT_PATTERN, tree[3])
|
|
if found:
|
|
self._docstring = eval(vars['docstring'])
|
|
# discover inner definitions
|
|
for node in tree[1:]:
|
|
found, vars = match(COMPOUND_STMT_PATTERN, node)
|
|
if found:
|
|
cstmt = vars['compound']
|
|
if cstmt[0] == symbol.funcdef:
|
|
name = cstmt[2][1]
|
|
self._function_info[name] = FunctionInfo(cstmt)
|
|
elif cstmt[0] == symbol.classdef:
|
|
name = cstmt[2][1]
|
|
self._class_info[name] = ClassInfo(cstmt)
|
|
|
|
After initializing some internal state, the constructor calls the
|
|
:meth:`_extract_info` method. This method performs the bulk of the information
|
|
extraction which takes place in the entire example. The extraction has two
|
|
distinct phases: the location of the docstring for the parse tree passed in, and
|
|
the discovery of additional definitions within the code block represented by the
|
|
parse tree.
|
|
|
|
The initial :keyword:`if` test determines whether the nested suite is of the
|
|
"short form" or the "long form." The short form is used when the code block is
|
|
on the same line as the definition of the code block, as in ::
|
|
|
|
def square(x): "Square an argument."; return x ** 2
|
|
|
|
while the long form uses an indented block and allows nested definitions::
|
|
|
|
def make_power(exp):
|
|
"Make a function that raises an argument to the exponent `exp'."
|
|
def raiser(x, y=exp):
|
|
return x ** y
|
|
return raiser
|
|
|
|
When the short form is used, the code block may contain a docstring as the
|
|
first, and possibly only, :const:`small_stmt` element. The extraction of such a
|
|
docstring is slightly different and requires only a portion of the complete
|
|
pattern used in the more common case. As implemented, the docstring will only
|
|
be found if there is only one :const:`small_stmt` node in the
|
|
:const:`simple_stmt` node. Since most functions and methods which use the short
|
|
form do not provide a docstring, this may be considered sufficient. The
|
|
extraction of the docstring proceeds using the :func:`match` function as
|
|
described above, and the value of the docstring is stored as an attribute of the
|
|
:class:`SuiteInfoBase` object.
|
|
|
|
After docstring extraction, a simple definition discovery algorithm operates on
|
|
the :const:`stmt` nodes of the :const:`suite` node. The special case of the
|
|
short form is not tested; since there are no :const:`stmt` nodes in the short
|
|
form, the algorithm will silently skip the single :const:`simple_stmt` node and
|
|
correctly not discover any nested definitions.
|
|
|
|
Each statement in the code block is categorized as a class definition, function
|
|
or method definition, or something else. For the definition statements, the
|
|
name of the element defined is extracted and a representation object appropriate
|
|
to the definition is created with the defining subtree passed as an argument to
|
|
the constructor. The representation objects are stored in instance variables
|
|
and may be retrieved by name using the appropriate accessor methods.
|
|
|
|
The public classes provide any accessors required which are more specific than
|
|
those provided by the :class:`SuiteInfoBase` class, but the real extraction
|
|
algorithm remains common to all forms of code blocks. A high-level function can
|
|
be used to extract the complete set of information from a source file. (See
|
|
file :file:`example.py`.) ::
|
|
|
|
def get_docs(fileName):
|
|
import os
|
|
import parser
|
|
|
|
source = open(fileName).read()
|
|
basename = os.path.basename(os.path.splitext(fileName)[0])
|
|
st = parser.suite(source)
|
|
return ModuleInfo(st.totuple(), basename)
|
|
|
|
This provides an easy-to-use interface to the documentation of a module. If
|
|
information is required which is not extracted by the code of this example, the
|
|
code may be extended at clearly defined points to provide additional
|
|
capabilities.
|
|
|