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- """ Pyparsing parser for BibTeX files
- A standalone parser using pyparsing.
- pyparsing has a simple and expressive syntax so the grammar is easy to read and
- write.
- Submitted by Matthew Brett, 2010
- Simplified BSD license
- """
- from pyparsing import (Regex, Suppress, ZeroOrMore, Group, Optional, Forward,
- SkipTo, CaselessLiteral, Dict)
- class Macro(object):
- """ Class to encapsulate undefined macro references """
- def __init__(self, name):
- self.name = name
- def __repr__(self):
- return 'Macro("%s")' % self.name
- def __eq__(self, other):
- return self.name == other.name
- def __ne__(self, other):
- return self.name != other.name
- # Character literals
- LCURLY,RCURLY,LPAREN,RPAREN,QUOTE,COMMA,AT,EQUALS,HASH = map(Suppress,'{}()",@=#')
- def bracketed(expr):
- """ Return matcher for `expr` between curly brackets or parentheses """
- return (LPAREN + expr + RPAREN) | (LCURLY + expr + RCURLY)
- # Define parser components for strings (the hard bit)
- chars_no_curly = Regex(r"[^{}]+")
- chars_no_curly.leaveWhitespace()
- chars_no_quotecurly = Regex(r'[^"{}]+')
- chars_no_quotecurly.leaveWhitespace()
- # Curly string is some stuff without curlies, or nested curly sequences
- curly_string = Forward()
- curly_item = Group(curly_string) | chars_no_curly
- curly_string << LCURLY + ZeroOrMore(curly_item) + RCURLY
- # quoted string is either just stuff within quotes, or stuff within quotes, within
- # which there is nested curliness
- quoted_item = Group(curly_string) | chars_no_quotecurly
- quoted_string = QUOTE + ZeroOrMore(quoted_item) + QUOTE
- # Numbers can just be numbers. Only integers though.
- number = Regex('[0-9]+')
- # Basis characters (by exclusion) for variable / field names. The following
- # list of characters is from the btparse documentation
- any_name = Regex('[^\\s"#%\'(),={}]+')
- # btparse says, and the test bibs show by experiment, that macro and field names
- # cannot start with a digit. In fact entry type names cannot start with a digit
- # either (see tests/bibs). Cite keys can start with a digit
- not_digname = Regex('[^\\d\\s"#%\'(),={}][^\\s"#%\'(),={}]*')
- # Comment comments out to end of line
- comment = (AT + CaselessLiteral('comment') +
- Regex(r"[\s{(].*").leaveWhitespace())
- # The name types with their digiteyness
- not_dig_lower = not_digname.copy().setParseAction(lambda t: t[0].lower())
- macro_def = not_dig_lower.copy()
- macro_ref = not_dig_lower.copy().setParseAction(lambda t : Macro(t[0].lower()))
- field_name = not_dig_lower.copy()
- # Spaces in names mean they cannot clash with field names
- entry_type = not_dig_lower('entry_type')
- cite_key = any_name('cite_key')
- # Number has to be before macro name
- string = (number | macro_ref | quoted_string | curly_string)
- # There can be hash concatenation
- field_value = string + ZeroOrMore(HASH + string)
- field_def = Group(field_name + EQUALS + field_value)
- entry_contents = Dict(ZeroOrMore(field_def + COMMA) + Optional(field_def))
- # Entry is surrounded either by parentheses or curlies
- entry = (AT + entry_type + bracketed(cite_key + COMMA + entry_contents))
- # Preamble is a macro-like thing with no name
- preamble = AT + CaselessLiteral('preamble') + bracketed(field_value)
- # Macros (aka strings)
- macro_contents = macro_def + EQUALS + field_value
- macro = AT + CaselessLiteral('string') + bracketed(macro_contents)
- # Implicit comments
- icomment = SkipTo('@').setParseAction(lambda t : t.insert(0, 'icomment'))
- # entries are last in the list (other than the fallback) because they have
- # arbitrary start patterns that would match comments, preamble or macro
- definitions = Group(comment |
- preamble |
- macro |
- entry |
- icomment)
- # Start symbol
- bibfile = ZeroOrMore(definitions)
- def parse_str(str):
- return bibfile.parseString(str)
- if __name__ == '__main__':
- # Run basic test
- txt = """
- Some introductory text
- (implicit comment)
- @ARTICLE{Authors2011,
- author = {First Author and Second Author and Third Author},
- title = {An article about {S}omething},
- journal = "Journal of Articles",
- year = {2011},
- volume = {16},
- pages = {1140--1141},
- number = {2}
- }
- """
- print('\n\n'.join(defn.dump() for defn in parse_str(txt)))
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