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- # pythonGrammarParser.py
- #
- # Copyright, 2006, by Paul McGuire
- #
- from pyparsing import *
- # should probably read this from the Grammar file provided with the Python source, but
- # this just skips that step and inlines the bnf text directly - this grammar was taken from
- # Python 2.4.1
- #
- grammar = r"""
- # Grammar for Python
- # Note: Changing the grammar specified in this file will most likely
- # require corresponding changes in the parser module
- # (../Modules/parsermodule.c). If you can't make the changes to
- # that module yourself, please co-ordinate the required changes
- # with someone who can; ask around on python-dev for help. Fred
- # Drake <fdrake@acm.org> will probably be listening there.
- # Commands for Kees Blom's railroad program
- #diagram:token NAME
- #diagram:token NUMBER
- #diagram:token STRING
- #diagram:token NEWLINE
- #diagram:token ENDMARKER
- #diagram:token INDENT
- #diagram:output\input python.bla
- #diagram:token DEDENT
- #diagram:output\textwidth 20.04cm\oddsidemargin 0.0cm\evensidemargin 0.0cm
- #diagram:rules
- # Start symbols for the grammar:
- # single_input is a single interactive statement;
- # file_input is a module or sequence of commands read from an input file;
- # eval_input is the input for the eval() and input() functions.
- # NB: compound_stmt in single_input is followed by extra NEWLINE!
- single_input: NEWLINE | simple_stmt | compound_stmt NEWLINE
- file_input: (NEWLINE | stmt)* ENDMARKER
- eval_input: testlist NEWLINE* ENDMARKER
- decorator: '@' dotted_name [ '(' [arglist] ')' ] NEWLINE
- decorators: decorator+
- funcdef: [decorators] 'def' NAME parameters ':' suite
- parameters: '(' [varargslist] ')'
- varargslist: (fpdef ['=' test] ',')* ('*' NAME [',' '**' NAME] | '**' NAME) | fpdef ['=' test] (',' fpdef ['=' test])* [',']
- fpdef: NAME | '(' fplist ')'
- fplist: fpdef (',' fpdef)* [',']
- stmt: simple_stmt | compound_stmt
- simple_stmt: small_stmt (';' small_stmt)* [';'] NEWLINE
- small_stmt: expr_stmt | print_stmt | del_stmt | pass_stmt | flow_stmt | import_stmt | global_stmt | exec_stmt | assert_stmt
- expr_stmt: testlist (augassign testlist | ('=' testlist)*)
- augassign: '+=' | '-=' | '*=' | '/=' | '%=' | '&=' | '|=' | '^=' | '<<=' | '>>=' | '**=' | '//='
- # For normal assignments, additional restrictions enforced by the interpreter
- print_stmt: 'print' ( [ test (',' test)* [','] ] | '>>' test [ (',' test)+ [','] ] )
- del_stmt: 'del' exprlist
- pass_stmt: 'pass'
- flow_stmt: break_stmt | continue_stmt | return_stmt | raise_stmt | yield_stmt
- break_stmt: 'break'
- continue_stmt: 'continue'
- return_stmt: 'return' [testlist]
- yield_stmt: 'yield' testlist
- raise_stmt: 'raise' [test [',' test [',' test]]]
- import_stmt: import_name | import_from
- import_name: 'import' dotted_as_names
- import_from: 'from' dotted_name 'import' ('*' | '(' import_as_names ')' | import_as_names)
- import_as_name: NAME [NAME NAME]
- dotted_as_name: dotted_name [NAME NAME]
- import_as_names: import_as_name (',' import_as_name)* [',']
- dotted_as_names: dotted_as_name (',' dotted_as_name)*
- dotted_name: NAME ('.' NAME)*
- global_stmt: 'global' NAME (',' NAME)*
- exec_stmt: 'exec' expr ['in' test [',' test]]
- assert_stmt: 'assert' test [',' test]
- #35
- compound_stmt: if_stmt | while_stmt | for_stmt | try_stmt | funcdef | classdef
- if_stmt: 'if' test ':' suite ('elif' test ':' suite)* ['else' ':' suite]
- while_stmt: 'while' test ':' suite ['else' ':' suite]
- for_stmt: 'for' exprlist 'in' testlist ':' suite ['else' ':' suite]
- try_stmt: ('try' ':' suite (except_clause ':' suite)+ #diagram:break
- ['else' ':' suite] | 'try' ':' suite 'finally' ':' suite)
- # NB compile.c makes sure that the default except clause is last
- except_clause: 'except' [test [',' test]]
- suite: simple_stmt | NEWLINE INDENT stmt+ DEDENT
- test: and_test ('or' and_test)* | lambdef
- and_test: not_test ('and' not_test)*
- not_test: 'not' not_test | comparison
- comparison: expr (comp_op expr)*
- comp_op: '<'|'>'|'=='|'>='|'<='|'<>'|'!='|'in'|'not' 'in'|'is'|'is' 'not'
- expr: xor_expr ('|' xor_expr)*
- xor_expr: and_expr ('^' and_expr)*
- and_expr: shift_expr ('&' shift_expr)*
- shift_expr: arith_expr (('<<'|'>>') arith_expr)*
- arith_expr: term (('+'|'-') term)*
- term: factor (('*'|'/'|'%'|'//') factor)*
- factor: ('+'|'-'|'~') factor | power
- power: atom trailer* ['**' factor]
- atom: '(' [testlist_gexp] ')' | '[' [listmaker] ']' | '{' [dictmaker] '}' | '`' testlist1 '`' | NAME | NUMBER | STRING+
- listmaker: test ( list_for | (',' test)* [','] )
- testlist_gexp: test ( gen_for | (',' test)* [','] )
- lambdef: 'lambda' [varargslist] ':' test
- trailer: '(' [arglist] ')' | '[' subscriptlist ']' | '.' NAME
- subscriptlist: subscript (',' subscript)* [',']
- subscript: '.' '.' '.' | test | [test] ':' [test] [sliceop]
- sliceop: ':' [test]
- exprlist: expr (',' expr)* [',']
- testlist: test (',' test)* [',']
- testlist_safe: test [(',' test)+ [',']]
- dictmaker: test ':' test (',' test ':' test)* [',']
- classdef: 'class' NAME ['(' testlist ')'] ':' suite
- arglist: (argument ',')* (argument [',']| '*' test [',' '**' test] | '**' test)
- argument: [test '='] test [gen_for] # Really [keyword '='] test
- list_iter: list_for | list_if
- list_for: 'for' exprlist 'in' testlist_safe [list_iter]
- list_if: 'if' test [list_iter]
- gen_iter: gen_for | gen_if
- gen_for: 'for' exprlist 'in' test [gen_iter]
- gen_if: 'if' test [gen_iter]
- testlist1: test (',' test)*
- # not used in grammar, but may appear in "node" passed from Parser to Compiler
- encoding_decl: NAME
- """
- class SemanticGroup(object):
- def __init__(self,contents):
- self.contents = contents
- while self.contents[-1].__class__ == self.__class__:
- self.contents = self.contents[:-1] + self.contents[-1].contents
- def __str__(self):
- return "{0}({1})".format(self.label,
- " ".join([isinstance(c,str) and c or str(c) for c in self.contents]) )
- class OrList(SemanticGroup):
- label = "OR"
- pass
- class AndList(SemanticGroup):
- label = "AND"
- pass
- class OptionalGroup(SemanticGroup):
- label = "OPT"
- pass
- class Atom(SemanticGroup):
- def __init__(self,contents):
- if len(contents) > 1:
- self.rep = contents[1]
- else:
- self.rep = ""
- if isinstance(contents,str):
- self.contents = contents
- else:
- self.contents = contents[0]
- def __str__(self):
- return "{0}{1}".format(self.rep, self.contents)
- def makeGroupObject(cls):
- def groupAction(s,l,t):
- try:
- return cls(t[0].asList())
- except Exception:
- return cls(t)
- return groupAction
- # bnf punctuation
- LPAREN = Suppress("(")
- RPAREN = Suppress(")")
- LBRACK = Suppress("[")
- RBRACK = Suppress("]")
- COLON = Suppress(":")
- ALT_OP = Suppress("|")
- # bnf grammar
- ident = Word(alphanums+"_")
- bnfToken = Word(alphanums+"_") + ~FollowedBy(":")
- repSymbol = oneOf("* +")
- bnfExpr = Forward()
- optionalTerm = Group(LBRACK + bnfExpr + RBRACK).setParseAction(makeGroupObject(OptionalGroup))
- bnfTerm = ( (bnfToken | quotedString | optionalTerm | ( LPAREN + bnfExpr + RPAREN )) + Optional(repSymbol) ).setParseAction(makeGroupObject(Atom))
- andList = Group(bnfTerm + OneOrMore(bnfTerm)).setParseAction(makeGroupObject(AndList))
- bnfFactor = andList | bnfTerm
- orList = Group( bnfFactor + OneOrMore( ALT_OP + bnfFactor ) ).setParseAction(makeGroupObject(OrList))
- bnfExpr << ( orList | bnfFactor )
- bnfLine = ident + COLON + bnfExpr
- bnfComment = "#" + restOfLine
- # build return tokens as a dictionary
- bnf = Dict(OneOrMore(Group(bnfLine)))
- bnf.ignore(bnfComment)
- # bnf is defined, parse the grammar text
- bnfDefs = bnf.parseString(grammar)
- # correct answer is 78
- expected = 78
- assert len(bnfDefs) == expected, \
- "Error, found %d BNF defns, expected %d" % (len(bnfDefs), expected)
- # list out defns in order they were parsed (to verify accuracy of parsing)
- for k,v in bnfDefs:
- print(k,"=",v)
- print()
- # list out parsed grammar defns (demonstrates dictionary access to parsed tokens)
- for k in list(bnfDefs.keys()):
- print(k,"=",bnfDefs[k])
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