/usr/lib/python3/dist-packages/parso/parser.py is in python3-parso 0.1.1-1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
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The ``Parser`` tries to convert the available Python code in an easy to read
format, something like an abstract syntax tree. The classes who represent this
tree, are sitting in the :mod:`parso.tree` module.
The Python module ``tokenize`` is a very important part in the ``Parser``,
because it splits the code into different words (tokens). Sometimes it looks a
bit messy. Sorry for that! You might ask now: "Why didn't you use the ``ast``
module for this? Well, ``ast`` does a very good job understanding proper Python
code, but fails to work as soon as there's a single line of broken code.
There's one important optimization that needs to be known: Statements are not
being parsed completely. ``Statement`` is just a representation of the tokens
within the statement. This lowers memory usage and cpu time and reduces the
complexity of the ``Parser`` (there's another parser sitting inside
``Statement``, which produces ``Array`` and ``Call``).
"""
from parso import tree
from parso.pgen2.parse import PgenParser
class ParserSyntaxError(Exception):
"""
Contains error information about the parser tree.
May be raised as an exception.
"""
def __init__(self, message, error_leaf):
self.message = message
self.error_leaf = error_leaf
class BaseParser(object):
node_map = {}
default_node = tree.Node
leaf_map = {
}
default_leaf = tree.Leaf
def __init__(self, pgen_grammar, start_symbol='file_input', error_recovery=False):
self._pgen_grammar = pgen_grammar
self._start_symbol = start_symbol
self._error_recovery = error_recovery
def parse(self, tokens):
start_number = self._pgen_grammar.symbol2number[self._start_symbol]
self.pgen_parser = PgenParser(
self._pgen_grammar, self.convert_node, self.convert_leaf,
self.error_recovery, start_number
)
node = self.pgen_parser.parse(tokens)
# The stack is empty now, we don't need it anymore.
del self.pgen_parser
return node
def error_recovery(self, pgen_grammar, stack, arcs, typ, value, start_pos, prefix,
add_token_callback):
if self._error_recovery:
raise NotImplementedError("Error Recovery is not implemented")
else:
error_leaf = tree.ErrorLeaf('TODO %s' % typ, value, start_pos, prefix)
raise ParserSyntaxError('SyntaxError: invalid syntax', error_leaf)
def convert_node(self, pgen_grammar, type_, children):
# TODO REMOVE symbol, we don't want type here.
symbol = pgen_grammar.number2symbol[type_]
try:
return self.node_map[symbol](children)
except KeyError:
return self.default_node(symbol, children)
def convert_leaf(self, pgen_grammar, type_, value, prefix, start_pos):
try:
return self.leaf_map[type_](value, start_pos, prefix)
except KeyError:
return self.default_leaf(value, start_pos, prefix)
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