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241 lines
6.6 KiB
Python
241 lines
6.6 KiB
Python
"""Object-oriented interface to the parser module.
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This module exports four classes which together provide an interface
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to the parser module. Together, the three classes represent two ways
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to create parsed representations of Python source and the two starting
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data types (source text and tuple representations). Each class
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provides interfaces which are identical other than the constructors.
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The constructors are described in detail in the documentation for each
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class and the remaining, shared portion of the interface is documented
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below. Briefly, the classes provided are:
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AST
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Defines the primary interface to the AST objects and supports creation
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from the tuple representation of the parse tree.
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ExpressionAST
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Supports creation of expression constructs from source text.
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SuiteAST
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Supports creation of statement suites from source text.
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FileSuiteAST
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Convenience subclass of the `SuiteAST' class; loads source text of the
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suite from an external file.
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Common Methods
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--------------
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Aside from the constructors, several methods are provided to allow
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access to the various interpretations of the parse tree and to check
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conditions of the construct represented by the parse tree.
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ast()
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Returns the corresponding `parser.ASTType' object.
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code()
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Returns the compiled code object.
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filename()
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Returns the name of the associated source file, if known.
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isExpression()
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Returns true value if parse tree represents an expression, or a false
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value otherwise.
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isSuite()
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Returns true value if parse tree represents a suite of statements, or
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a false value otherwise.
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text()
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Returns the source text, or None if not available.
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tuple()
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Returns the tuple representing the parse tree.
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"""
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__version__ = '$Revision$'
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__copyright__ = """Copyright (c) 1995, 1996 by Fred L. Drake, Jr.
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This software may be used and distributed freely for any purpose provided
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that this notice is included unchanged on any and all copies. The author
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does not warrant or guarantee this software in any way.
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"""
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class AST:
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"""Base class for Abstract Syntax Tree objects.
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Creates an Abstract Syntax Tree based on the tuple representation
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of the parse tree. The parse tree can represent either an
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expression or a suite; which will be recognized automatically.
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This base class provides all of the query methods for subclass
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objects defined in this module.
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"""
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import parser # import internally to avoid
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_p = parser # namespace pollution at the
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# top level
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_text = None
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_code = None
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_ast = None
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_type = 'unknown'
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_tupl = None
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def __init__(self, tuple):
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"""Create an `AST' instance from a tuple-tree representation.
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tuple
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The tuple tree to convert.
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The tuple-tree may represent either an expression or a suite; the
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type will be determined automatically. Line number information may
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optionally be present for any subset of the terminal tokens.
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"""
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if type(tuple) is not type(()):
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raise TypeError, 'Base AST class requires tuple parameter.'
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self._tupl = tuple
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self._ast = self._p.tuple2ast(tuple)
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self._type = (self._p.isexpr(self._ast) and 'expression') or 'suite'
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def list(self, line_info = 0):
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"""Returns a fresh list representing the parse tree.
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line_info
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If true, includes line number information for terminal tokens in
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the output data structure,
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"""
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return self._p.ast2list(self._ast, line_info)
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def tuple(self, line_info = 0):
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"""Returns the tuple representing the parse tree.
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line_info
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If true, includes line number information for terminal tokens in
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the output data structure,
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"""
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if self._tupl is None:
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self._tupl = self._p.ast2tuple(self._ast, line_info)
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return self._tupl
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def code(self):
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"""Returns the compiled code object.
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The code object returned by this method may be passed to the
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exec statement if `AST.isSuite()' is true or to the eval()
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function if `AST.isExpression()' is true. All the usual rules
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regarding execution of code objects apply.
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"""
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if not self._code:
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self._code = self._p.compileast(self._ast)
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return self._code
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def ast(self):
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"""Returns the corresponding `parser.ASTType' object.
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"""
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return self._ast
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def filename(self):
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"""Returns the name of the source file if known, or None.
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"""
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return None
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def text(self):
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"""Returns the source text, or None if not available.
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If the instance is of class `AST', None is returned since no
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source text is available. If of class `ExpressionAST' or
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`SuiteAST', the source text passed to the constructor is
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returned.
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"""
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return self._text
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def isSuite(self):
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"""Determine if `AST' instance represents a suite of statements.
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"""
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return self._type == 'suite'
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def isExpression(self):
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"""Determine if `AST' instance represents an expression.
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"""
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return self._type == 'expression'
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class SuiteAST(AST):
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"""Statement suite parse tree representation.
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This subclass of the `AST' base class represents statement suites
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parsed from the source text of a Python suite. If the source text
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does not represent a parsable suite of statements, the appropriate
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exception is raised by the parser.
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"""
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_type = 'suite'
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def __init__(self, text):
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"""Initialize a `SuiteAST' from source text.
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text
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Source text to parse.
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"""
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if type(text) is not type(''):
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raise TypeError, 'SuiteAST requires source text parameter.'
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self._text = text
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self._ast = self._p.suite(text)
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def isSuite(self):
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return 1
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def isExpression(self):
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return 0
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class FileSuiteAST(SuiteAST):
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"""Representation of a python source file syntax tree.
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This provides a convenience wrapper around the `SuiteAST' class to
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load the source text from an external file.
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"""
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def __init__(self, fileName):
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"""Initialize a `SuiteAST' from a source file.
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fileName
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Name of the external source file.
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"""
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self._fileName = fileName
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SuiteAST.__init__(self, open(fileName).read())
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def filename(self):
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return self._fileName
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class ExpressionAST(AST):
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"""Expression parse tree representation.
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This subclass of the `AST' base class represents expression
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constructs parsed from the source text of a Python expression. If
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the source text does not represent a parsable expression, the
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appropriate exception is raised by the Python parser.
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"""
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_type = 'expression'
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def __init__(self, text):
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"""Initialize an expression AST from source text.
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text
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Source text to parse.
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"""
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if type(text) is not type(''):
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raise TypeError, 'ExpressionAST requires source text parameter.'
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self._text = text
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self._ast = self._p.expr(text)
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def isSuite(self):
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return 0
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def isExpression(self):
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return 1
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#
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# end of file
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