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|
# actions.py
from .exceptions import ParseException
from .util import col
class OnlyOnce:
"""
Wrapper for parse actions, to ensure they are only called once.
"""
def __init__(self, method_call):
from .core import _trim_arity
self.callable = _trim_arity(method_call)
self.called = False
def __call__(self, s, l, t):
if not self.called:
results = self.callable(s, l, t)
self.called = True
return results
raise ParseException(s, l, "OnlyOnce obj called multiple times w/out reset")
def reset(self):
"""
Allow the associated parse action to be called once more.
"""
self.called = False
def match_only_at_col(n):
"""
Helper method for defining parse actions that require matching at
a specific column in the input text.
"""
def verify_col(strg, locn, toks):
if col(locn, strg) != n:
raise ParseException(strg, locn, "matched token not at column {}".format(n))
return verify_col
def replace_with(repl_str):
"""
Helper method for common parse actions that simply return
a literal value. Especially useful when used with
:class:`transform_string<ParserElement.transform_string>` ().
Example::
num = Word(nums).set_parse_action(lambda toks: int(toks[0]))
na = one_of("N/A NA").set_parse_action(replace_with(math.nan))
term = na | num
term[1, ...].parse_string("324 234 N/A 234") # -> [324, 234, nan, 234]
"""
return lambda s, l, t: [repl_str]
def remove_quotes(s, l, t):
"""
Helper parse action for removing quotation marks from parsed
quoted strings.
Example::
# by default, quotation marks are included in parsed results
quoted_string.parse_string("'Now is the Winter of our Discontent'") # -> ["'Now is the Winter of our Discontent'"]
# use remove_quotes to strip quotation marks from parsed results
quoted_string.set_parse_action(remove_quotes)
quoted_string.parse_string("'Now is the Winter of our Discontent'") # -> ["Now is the Winter of our Discontent"]
"""
return t[0][1:-1]
def with_attribute(*args, **attr_dict):
"""
Helper to create a validating parse action to be used with start
tags created with :class:`make_xml_tags` or
:class:`make_html_tags`. Use ``with_attribute`` to qualify
a starting tag with a required attribute value, to avoid false
matches on common tags such as ``<TD>`` or ``<DIV>``.
Call ``with_attribute`` with a series of attribute names and
values. Specify the list of filter attributes names and values as:
- keyword arguments, as in ``(align="right")``, or
- as an explicit dict with ``**`` operator, when an attribute
name is also a Python reserved word, as in ``**{"class":"Customer", "align":"right"}``
- a list of name-value tuples, as in ``(("ns1:class", "Customer"), ("ns2:align", "right"))``
For attribute names with a namespace prefix, you must use the second
form. Attribute names are matched insensitive to upper/lower case.
If just testing for ``class`` (with or without a namespace), use
:class:`with_class`.
To verify that the attribute exists, but without specifying a value,
pass ``with_attribute.ANY_VALUE`` as the value.
Example::
html = '''
<div>
Some text
<div type="grid">1 4 0 1 0</div>
<div type="graph">1,3 2,3 1,1</div>
<div>this has no type</div>
</div>
'''
div,div_end = make_html_tags("div")
# only match div tag having a type attribute with value "grid"
div_grid = div().set_parse_action(with_attribute(type="grid"))
grid_expr = div_grid + SkipTo(div | div_end)("body")
for grid_header in grid_expr.search_string(html):
print(grid_header.body)
# construct a match with any div tag having a type attribute, regardless of the value
div_any_type = div().set_parse_action(with_attribute(type=with_attribute.ANY_VALUE))
div_expr = div_any_type + SkipTo(div | div_end)("body")
for div_header in div_expr.search_string(html):
print(div_header.body)
prints::
1 4 0 1 0
1 4 0 1 0
1,3 2,3 1,1
"""
if args:
attrs = args[:]
else:
attrs = attr_dict.items()
attrs = [(k, v) for k, v in attrs]
def pa(s, l, tokens):
for attrName, attrValue in attrs:
if attrName not in tokens:
raise ParseException(s, l, "no matching attribute " + attrName)
if attrValue != with_attribute.ANY_VALUE and tokens[attrName] != attrValue:
raise ParseException(
s,
l,
"attribute {!r} has value {!r}, must be {!r}".format(
attrName, tokens[attrName], attrValue
),
)
return pa
with_attribute.ANY_VALUE = object()
def with_class(classname, namespace=""):
"""
Simplified version of :class:`with_attribute` when
matching on a div class - made difficult because ``class`` is
a reserved word in Python.
Example::
html = '''
<div>
Some text
<div class="grid">1 4 0 1 0</div>
<div class="graph">1,3 2,3 1,1</div>
<div>this <div> has no class</div>
</div>
'''
div,div_end = make_html_tags("div")
div_grid = div().set_parse_action(with_class("grid"))
grid_expr = div_grid + SkipTo(div | div_end)("body")
for grid_header in grid_expr.search_string(html):
print(grid_header.body)
div_any_type = div().set_parse_action(with_class(withAttribute.ANY_VALUE))
div_expr = div_any_type + SkipTo(div | div_end)("body")
for div_header in div_expr.search_string(html):
print(div_header.body)
prints::
1 4 0 1 0
1 4 0 1 0
1,3 2,3 1,1
"""
classattr = "{}:class".format(namespace) if namespace else "class"
return with_attribute(**{classattr: classname})
# pre-PEP8 compatibility symbols
replaceWith = replace_with
removeQuotes = remove_quotes
withAttribute = with_attribute
withClass = with_class
matchOnlyAtCol = match_only_at_col
|
