286 lines
7.1 KiB
Python
286 lines
7.1 KiB
Python
|
"""
|
||
|
|
A simple XPath-like language for tree traversal.
|
||
|
|
|
||
|
|
This works by creating a filter chain of generator functions. Each
|
||
|
|
function selects a part of the expression, e.g. a child node, a
|
||
|
|
specific descendant or a node that holds an attribute.
|
||
|
|
"""
|
||
|
|
|
||
|
|
from __future__ import absolute_import
|
||
|
|
|
||
|
|
import re
|
||
|
|
import operator
|
||
|
|
|
||
|
|
path_tokenizer = re.compile(
|
||
|
|
r"("
|
||
|
|
r"'[^']*'|\"[^\"]*\"|"
|
||
|
|
r"//?|"
|
||
|
|
r"\(\)|"
|
||
|
|
r"==?|"
|
||
|
|
r"[/.*\[\]()@])|"
|
||
|
|
r"([^/\[\]()@=\s]+)|"
|
||
|
|
r"\s+"
|
||
|
|
).findall
|
||
|
|
|
||
|
|
def iterchildren(node, attr_name):
|
||
|
|
# returns an iterable of all child nodes of that name
|
||
|
|
child = getattr(node, attr_name)
|
||
|
|
if child is not None:
|
||
|
|
if type(child) is list:
|
||
|
|
return child
|
||
|
|
else:
|
||
|
|
return [child]
|
||
|
|
else:
|
||
|
|
return ()
|
||
|
|
|
||
|
|
def _get_first_or_none(it):
|
||
|
|
try:
|
||
|
|
try:
|
||
|
|
_next = it.next
|
||
|
|
except AttributeError:
|
||
|
|
return next(it)
|
||
|
|
else:
|
||
|
|
return _next()
|
||
|
|
except StopIteration:
|
||
|
|
return None
|
||
|
|
|
||
|
|
def type_name(node):
|
||
|
|
return node.__class__.__name__.split('.')[-1]
|
||
|
|
|
||
|
|
def parse_func(next, token):
|
||
|
|
name = token[1]
|
||
|
|
token = next()
|
||
|
|
if token[0] != '(':
|
||
|
|
raise ValueError("Expected '(' after function name '%s'" % name)
|
||
|
|
predicate = handle_predicate(next, token)
|
||
|
|
return name, predicate
|
||
|
|
|
||
|
|
def handle_func_not(next, token):
|
||
|
|
"""
|
||
|
|
not(...)
|
||
|
|
"""
|
||
|
|
name, predicate = parse_func(next, token)
|
||
|
|
|
||
|
|
def select(result):
|
||
|
|
for node in result:
|
||
|
|
if _get_first_or_none(predicate([node])) is None:
|
||
|
|
yield node
|
||
|
|
return select
|
||
|
|
|
||
|
|
def handle_name(next, token):
|
||
|
|
"""
|
||
|
|
/NodeName/
|
||
|
|
or
|
||
|
|
func(...)
|
||
|
|
"""
|
||
|
|
name = token[1]
|
||
|
|
if name in functions:
|
||
|
|
return functions[name](next, token)
|
||
|
|
def select(result):
|
||
|
|
for node in result:
|
||
|
|
for attr_name in node.child_attrs:
|
||
|
|
for child in iterchildren(node, attr_name):
|
||
|
|
if type_name(child) == name:
|
||
|
|
yield child
|
||
|
|
return select
|
||
|
|
|
||
|
|
def handle_star(next, token):
|
||
|
|
"""
|
||
|
|
/*/
|
||
|
|
"""
|
||
|
|
def select(result):
|
||
|
|
for node in result:
|
||
|
|
for name in node.child_attrs:
|
||
|
|
for child in iterchildren(node, name):
|
||
|
|
yield child
|
||
|
|
return select
|
||
|
|
|
||
|
|
def handle_dot(next, token):
|
||
|
|
"""
|
||
|
|
/./
|
||
|
|
"""
|
||
|
|
def select(result):
|
||
|
|
return result
|
||
|
|
return select
|
||
|
|
|
||
|
|
def handle_descendants(next, token):
|
||
|
|
"""
|
||
|
|
//...
|
||
|
|
"""
|
||
|
|
token = next()
|
||
|
|
if token[0] == "*":
|
||
|
|
def iter_recursive(node):
|
||
|
|
for name in node.child_attrs:
|
||
|
|
for child in iterchildren(node, name):
|
||
|
|
yield child
|
||
|
|
for c in iter_recursive(child):
|
||
|
|
yield c
|
||
|
|
elif not token[0]:
|
||
|
|
node_name = token[1]
|
||
|
|
def iter_recursive(node):
|
||
|
|
for name in node.child_attrs:
|
||
|
|
for child in iterchildren(node, name):
|
||
|
|
if type_name(child) == node_name:
|
||
|
|
yield child
|
||
|
|
for c in iter_recursive(child):
|
||
|
|
yield c
|
||
|
|
else:
|
||
|
|
raise ValueError("Expected node name after '//'")
|
||
|
|
|
||
|
|
def select(result):
|
||
|
|
for node in result:
|
||
|
|
for child in iter_recursive(node):
|
||
|
|
yield child
|
||
|
|
|
||
|
|
return select
|
||
|
|
|
||
|
|
|
||
|
|
def handle_attribute(next, token):
|
||
|
|
token = next()
|
||
|
|
if token[0]:
|
||
|
|
raise ValueError("Expected attribute name")
|
||
|
|
name = token[1]
|
||
|
|
value = None
|
||
|
|
try:
|
||
|
|
token = next()
|
||
|
|
except StopIteration:
|
||
|
|
pass
|
||
|
|
else:
|
||
|
|
if token[0] == '=':
|
||
|
|
value = parse_path_value(next)
|
||
|
|
readattr = operator.attrgetter(name)
|
||
|
|
if value is None:
|
||
|
|
def select(result):
|
||
|
|
for node in result:
|
||
|
|
try:
|
||
|
|
attr_value = readattr(node)
|
||
|
|
except AttributeError:
|
||
|
|
continue
|
||
|
|
if attr_value is not None:
|
||
|
|
yield attr_value
|
||
|
|
else:
|
||
|
|
def select(result):
|
||
|
|
for node in result:
|
||
|
|
try:
|
||
|
|
attr_value = readattr(node)
|
||
|
|
except AttributeError:
|
||
|
|
continue
|
||
|
|
if attr_value == value:
|
||
|
|
yield attr_value
|
||
|
|
return select
|
||
|
|
|
||
|
|
|
||
|
|
def parse_path_value(next):
|
||
|
|
token = next()
|
||
|
|
value = token[0]
|
||
|
|
if value:
|
||
|
|
if value[:1] == "'" or value[:1] == '"':
|
||
|
|
return value[1:-1]
|
||
|
|
try:
|
||
|
|
return int(value)
|
||
|
|
except ValueError:
|
||
|
|
pass
|
||
|
|
elif token[1].isdigit():
|
||
|
|
return int(token[1])
|
||
|
|
else:
|
||
|
|
name = token[1].lower()
|
||
|
|
if name == 'true':
|
||
|
|
return True
|
||
|
|
elif name == 'false':
|
||
|
|
return False
|
||
|
|
raise ValueError("Invalid attribute predicate: '%s'" % value)
|
||
|
|
|
||
|
|
def handle_predicate(next, token):
|
||
|
|
token = next()
|
||
|
|
selector = []
|
||
|
|
while token[0] != ']':
|
||
|
|
selector.append( operations[token[0]](next, token) )
|
||
|
|
try:
|
||
|
|
token = next()
|
||
|
|
except StopIteration:
|
||
|
|
break
|
||
|
|
else:
|
||
|
|
if token[0] == "/":
|
||
|
|
token = next()
|
||
|
|
|
||
|
|
if not token[0] and token[1] == 'and':
|
||
|
|
return logical_and(selector, handle_predicate(next, token))
|
||
|
|
|
||
|
|
def select(result):
|
||
|
|
for node in result:
|
||
|
|
subresult = iter((node,))
|
||
|
|
for select in selector:
|
||
|
|
subresult = select(subresult)
|
||
|
|
predicate_result = _get_first_or_none(subresult)
|
||
|
|
if predicate_result is not None:
|
||
|
|
yield node
|
||
|
|
return select
|
||
|
|
|
||
|
|
def logical_and(lhs_selects, rhs_select):
|
||
|
|
def select(result):
|
||
|
|
for node in result:
|
||
|
|
subresult = iter((node,))
|
||
|
|
for select in lhs_selects:
|
||
|
|
subresult = select(subresult)
|
||
|
|
predicate_result = _get_first_or_none(subresult)
|
||
|
|
subresult = iter((node,))
|
||
|
|
if predicate_result is not None:
|
||
|
|
for result_node in rhs_select(subresult):
|
||
|
|
yield node
|
||
|
|
return select
|
||
|
|
|
||
|
|
|
||
|
|
operations = {
|
||
|
|
"@": handle_attribute,
|
||
|
|
"": handle_name,
|
||
|
|
"*": handle_star,
|
||
|
|
".": handle_dot,
|
||
|
|
"//": handle_descendants,
|
||
|
|
"[": handle_predicate,
|
||
|
|
}
|
||
|
|
|
||
|
|
functions = {
|
||
|
|
'not' : handle_func_not
|
||
|
|
}
|
||
|
|
|
||
|
|
def _build_path_iterator(path):
|
||
|
|
# parse pattern
|
||
|
|
stream = iter([ (special,text)
|
||
|
|
for (special,text) in path_tokenizer(path)
|
||
|
|
if special or text ])
|
||
|
|
try:
|
||
|
|
_next = stream.next
|
||
|
|
except AttributeError:
|
||
|
|
# Python 3
|
||
|
|
def _next():
|
||
|
|
return next(stream)
|
||
|
|
token = _next()
|
||
|
|
selector = []
|
||
|
|
while 1:
|
||
|
|
try:
|
||
|
|
selector.append(operations[token[0]](_next, token))
|
||
|
|
except StopIteration:
|
||
|
|
raise ValueError("invalid path")
|
||
|
|
try:
|
||
|
|
token = _next()
|
||
|
|
if token[0] == "/":
|
||
|
|
token = _next()
|
||
|
|
except StopIteration:
|
||
|
|
break
|
||
|
|
return selector
|
||
|
|
|
||
|
|
# main module API
|
||
|
|
|
||
|
|
def iterfind(node, path):
|
||
|
|
selector_chain = _build_path_iterator(path)
|
||
|
|
result = iter((node,))
|
||
|
|
for select in selector_chain:
|
||
|
|
result = select(result)
|
||
|
|
return result
|
||
|
|
|
||
|
|
def find_first(node, path):
|
||
|
|
return _get_first_or_none(iterfind(node, path))
|
||
|
|
|
||
|
|
def find_all(node, path):
|
||
|
|
return list(iterfind(node, path))
|