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Filter SelectorList with custom predicate? #142

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msukmanowsky opened this issue Jul 26, 2019 · 1 comment
Open

Filter SelectorList with custom predicate? #142

msukmanowsky opened this issue Jul 26, 2019 · 1 comment
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@msukmanowsky
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Somewhat related to #129, I'm curious if there's a way to filter a selector list using some manual predicate instead of doing a destructive removal as #129 is going for.

Something like this:

def is_good_node(node):
    return node.xpath("./@class").get() != "taboola"


selector = Selector(text="""
    <html>
        <body>
            <div class="content">
                Content
            </div>
            <div class="taboola">
                Taboola
            </div>
        </body>
    </html>
""")
nodes = selector.xpath("//*[not(self::a)]")
nodes = [node for node in nodes if is_good_node(node)]
nodes = SelectorList(nodes)
print(''.join(nodes.extract()))
# this prints
'''
<html>
        <body>
            <div class="content">
                Content
            </div>
            <div class="taboola">
                Taboola
            </div>
        </body>
    </html><body>
            <div class="content">
                Content
            </div>
            <div class="taboola">
                Taboola
            </div>
        </body><div class="content">
                Content
            </div>
'''

Assume is_good_node is more complex than the example above as I realize that particular predicate could be represented as an XPATH expression.

I've tried this approach and it doesn't work (ends up adding filtered nodes to the original document). Had a look at the source and didn't see an obvious way to do it with my limited lxml foo.
@Gallaecio
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So you are suggesting something like SelectorList.filter(my_filter_function)?

I guess it’s a valid feature request, although I’m not sure if I like it.

I assume the implementation would be as simple as:

def filter(self, filter):
    for selector in self:
        if filter(selector):
            yield selector

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@msukmanowsky @Gallaecio