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https://github.com/element-hq/synapse
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Merge pull request #973 from matrix-org/erikj/xpath_fix
Change the way we summarize URLs
This commit is contained in:
commit
a5d7968b3e
2 changed files with 211 additions and 14 deletions
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@ -29,6 +29,8 @@ from synapse.http.server import (
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from synapse.util.async import ObservableDeferred
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from synapse.util.stringutils import is_ascii
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from copy import deepcopy
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import os
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import re
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import fnmatch
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@ -329,20 +331,23 @@ class PreviewUrlResource(Resource):
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# ...or if they are within a <script/> or <style/> tag.
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# This is a very very very coarse approximation to a plain text
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# render of the page.
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text_nodes = tree.xpath("//text()[not(ancestor::header | ancestor::nav | "
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"ancestor::aside | ancestor::footer | "
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"ancestor::script | ancestor::style)]" +
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"[ancestor::body]")
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text = ''
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for text_node in text_nodes:
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if len(text) < 500:
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text += text_node + ' '
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else:
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break
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text = re.sub(r'[\t ]+', ' ', text)
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text = re.sub(r'[\t \r\n]*[\r\n]+', '\n', text)
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text = text.strip()[:500]
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og['og:description'] = text if text else None
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# We don't just use XPATH here as that is slow on some machines.
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# We clone `tree` as we modify it.
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cloned_tree = deepcopy(tree.find("body"))
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TAGS_TO_REMOVE = ("header", "nav", "aside", "footer", "script", "style",)
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for el in cloned_tree.iter(TAGS_TO_REMOVE):
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el.getparent().remove(el)
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# Split all the text nodes into paragraphs (by splitting on new
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# lines)
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text_nodes = (
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re.sub(r'\s+', '\n', el.text).strip()
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for el in cloned_tree.iter() if el.text
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)
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og['og:description'] = summarize_paragraphs(text_nodes)
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# TODO: delete the url downloads to stop diskfilling,
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# as we only ever cared about its OG
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@ -450,3 +455,56 @@ class PreviewUrlResource(Resource):
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content_type.startswith("application/xhtml")
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):
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return True
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def summarize_paragraphs(text_nodes, min_size=200, max_size=500):
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# Try to get a summary of between 200 and 500 words, respecting
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# first paragraph and then word boundaries.
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# TODO: Respect sentences?
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description = ''
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# Keep adding paragraphs until we get to the MIN_SIZE.
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for text_node in text_nodes:
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if len(description) < min_size:
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text_node = re.sub(r'[\t \r\n]+', ' ', text_node)
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description += text_node + '\n\n'
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else:
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break
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description = description.strip()
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description = re.sub(r'[\t ]+', ' ', description)
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description = re.sub(r'[\t \r\n]*[\r\n]+', '\n\n', description)
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# If the concatenation of paragraphs to get above MIN_SIZE
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# took us over MAX_SIZE, then we need to truncate mid paragraph
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if len(description) > max_size:
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new_desc = ""
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# This splits the paragraph into words, but keeping the
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# (preceeding) whitespace intact so we can easily concat
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# words back together.
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for match in re.finditer("\s*\S+", description):
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word = match.group()
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# Keep adding words while the total length is less than
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# MAX_SIZE.
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if len(word) + len(new_desc) < max_size:
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new_desc += word
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else:
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# At this point the next word *will* take us over
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# MAX_SIZE, but we also want to ensure that its not
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# a huge word. If it is add it anyway and we'll
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# truncate later.
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if len(new_desc) < min_size:
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new_desc += word
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break
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# Double check that we're not over the limit
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if len(new_desc) > max_size:
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new_desc = new_desc[:max_size]
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# We always add an ellipsis because at the very least
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# we chopped mid paragraph.
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description = new_desc.strip() + "…"
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return description if description else None
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139
tests/test_preview.py
Normal file
139
tests/test_preview.py
Normal file
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@ -0,0 +1,139 @@
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# -*- coding: utf-8 -*-
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# Copyright 2014-2016 OpenMarket Ltd
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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from . import unittest
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from synapse.rest.media.v1.preview_url_resource import summarize_paragraphs
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class PreviewTestCase(unittest.TestCase):
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def test_long_summarize(self):
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example_paras = [
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"""Tromsø (Norwegian pronunciation: [ˈtrʊmsœ] ( listen); Northern Sami:
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Romsa; Finnish: Tromssa[2] Kven: Tromssa) is a city and municipality in
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Troms county, Norway. The administrative centre of the municipality is
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the city of Tromsø. Outside of Norway, Tromso and Tromsö are
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alternative spellings of the city.Tromsø is considered the northernmost
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city in the world with a population above 50,000. The most populous town
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north of it is Alta, Norway, with a population of 14,272 (2013).""",
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"""Tromsø lies in Northern Norway. The municipality has a population of
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(2015) 72,066, but with an annual influx of students it has over 75,000
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most of the year. It is the largest urban area in Northern Norway and the
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third largest north of the Arctic Circle (following Murmansk and Norilsk).
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Most of Tromsø, including the city centre, is located on the island of
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Tromsøya, 350 kilometres (217 mi) north of the Arctic Circle. In 2012,
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Tromsøya had a population of 36,088. Substantial parts of the urban area
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are also situated on the mainland to the east, and on parts of Kvaløya—a
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large island to the west. Tromsøya is connected to the mainland by the Tromsø
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Bridge and the Tromsøysund Tunnel, and to the island of Kvaløya by the
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Sandnessund Bridge. Tromsø Airport connects the city to many destinations
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in Europe. The city is warmer than most other places located on the same
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latitude, due to the warming effect of the Gulf Stream.""",
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"""The city centre of Tromsø contains the highest number of old wooden
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houses in Northern Norway, the oldest house dating from 1789. The Arctic
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Cathedral, a modern church from 1965, is probably the most famous landmark
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in Tromsø. The city is a cultural centre for its region, with several
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festivals taking place in the summer. Some of Norway's best-known
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musicians, Torbjørn Brundtland and Svein Berge of the electronica duo
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Röyksopp and Lene Marlin grew up and started their careers in Tromsø.
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Noted electronic musician Geir Jenssen also hails from Tromsø.""",
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]
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desc = summarize_paragraphs(example_paras, min_size=200, max_size=500)
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self.assertEquals(
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desc,
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"Tromsø (Norwegian pronunciation: [ˈtrʊmsœ] ( listen); Northern Sami:"
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" Romsa; Finnish: Tromssa[2] Kven: Tromssa) is a city and municipality in"
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" Troms county, Norway. The administrative centre of the municipality is"
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" the city of Tromsø. Outside of Norway, Tromso and Tromsö are"
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" alternative spellings of the city.Tromsø is considered the northernmost"
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" city in the world with a population above 50,000. The most populous town"
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" north of it is Alta, Norway, with a population of 14,272 (2013)."
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)
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desc = summarize_paragraphs(example_paras[1:], min_size=200, max_size=500)
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self.assertEquals(
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desc,
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"Tromsø lies in Northern Norway. The municipality has a population of"
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" (2015) 72,066, but with an annual influx of students it has over 75,000"
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" most of the year. It is the largest urban area in Northern Norway and the"
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" third largest north of the Arctic Circle (following Murmansk and Norilsk)."
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" Most of Tromsø, including the city centre, is located on the island of"
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" Tromsøya, 350 kilometres (217 mi) north of the Arctic Circle. In 2012,"
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" Tromsøya had a population of 36,088. Substantial parts of the…"
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)
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def test_short_summarize(self):
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example_paras = [
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"Tromsø (Norwegian pronunciation: [ˈtrʊmsœ] ( listen); Northern Sami:"
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" Romsa; Finnish: Tromssa[2] Kven: Tromssa) is a city and municipality in"
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" Troms county, Norway.",
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"Tromsø lies in Northern Norway. The municipality has a population of"
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" (2015) 72,066, but with an annual influx of students it has over 75,000"
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" most of the year.",
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"The city centre of Tromsø contains the highest number of old wooden"
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" houses in Northern Norway, the oldest house dating from 1789. The Arctic"
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" Cathedral, a modern church from 1965, is probably the most famous landmark"
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" in Tromsø.",
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]
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desc = summarize_paragraphs(example_paras, min_size=200, max_size=500)
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self.assertEquals(
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desc,
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"Tromsø (Norwegian pronunciation: [ˈtrʊmsœ] ( listen); Northern Sami:"
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" Romsa; Finnish: Tromssa[2] Kven: Tromssa) is a city and municipality in"
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" Troms county, Norway.\n"
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"\n"
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"Tromsø lies in Northern Norway. The municipality has a population of"
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" (2015) 72,066, but with an annual influx of students it has over 75,000"
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" most of the year."
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)
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def test_small_then_large_summarize(self):
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example_paras = [
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"Tromsø (Norwegian pronunciation: [ˈtrʊmsœ] ( listen); Northern Sami:"
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" Romsa; Finnish: Tromssa[2] Kven: Tromssa) is a city and municipality in"
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" Troms county, Norway.",
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"Tromsø lies in Northern Norway. The municipality has a population of"
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" (2015) 72,066, but with an annual influx of students it has over 75,000"
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" most of the year."
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" The city centre of Tromsø contains the highest number of old wooden"
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" houses in Northern Norway, the oldest house dating from 1789. The Arctic"
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" Cathedral, a modern church from 1965, is probably the most famous landmark"
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" in Tromsø.",
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]
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desc = summarize_paragraphs(example_paras, min_size=200, max_size=500)
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self.assertEquals(
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desc,
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"Tromsø (Norwegian pronunciation: [ˈtrʊmsœ] ( listen); Northern Sami:"
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" Romsa; Finnish: Tromssa[2] Kven: Tromssa) is a city and municipality in"
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" Troms county, Norway.\n"
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"\n"
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"Tromsø lies in Northern Norway. The municipality has a population of"
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" (2015) 72,066, but with an annual influx of students it has over 75,000"
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" most of the year. The city centre of Tromsø contains the highest number"
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" of old wooden houses in Northern Norway, the oldest house dating from"
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" 1789. The Arctic Cathedral, a modern church…"
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)
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