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import re
from lxml import etree
from six import string_types
from w3lib.html import HTML5_WHITESPACE
regex = '[{}]+'.format(HTML5_WHITESPACE)
replace_html5_whitespaces = re.compile(regex).sub
def set_xpathfunc(fname, func):
"""Register a custom extension function to use in XPath expressions.
The function ``func`` registered under ``fname`` identifier will be called
for every matching node, being passed a ``context`` parameter as well as
any parameters passed from the corresponding XPath expression.
If ``func`` is ``None``, the extension function will be removed.
See more `in lxml documentation`_.
.. _`in lxml documentation`: http://lxml.de/extensions.html#xpath-extension-functions
"""
ns_fns = etree.FunctionNamespace(None)
if func is not None:
ns_fns[fname] = func
else:
del ns_fns[fname]
def setup():
set_xpathfunc('has-class', has_class)
def has_class(context, *classes):
"""has-class function.
Return True if all ``classes`` are present in element's class attr.
"""
if not context.eval_context.get('args_checked'):
if not classes:
raise ValueError(
'XPath error: has-class must have at least 1 argument')
for c in classes:
if not isinstance(c, string_types):
raise ValueError(
'XPath error: has-class arguments must be strings')
context.eval_context['args_checked'] = True
node_cls = context.context_node.get('class')
if node_cls is None:
return False
node_cls = ' ' + node_cls + ' '
node_cls = replace_html5_whitespaces(' ', node_cls)
for cls in classes:
if ' ' + cls + ' ' not in node_cls:
return False
return True
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