python - failed in installing Scikit-learn in ubuntu 16.04 - Ask Ubuntu

i trying install scikit-learn in ubuntu 16.04, there error when trying install. had installed following packages

python 2.7.12

numpy 1.11.0

scipy 0.17.0

but output of command pip install -u scikit-learn is

collecting scikit-learn exception: traceback (most recent call last):   file "/usr/lib/python2.7/dist-packages/pip/basecommand.py", line 209, in main     status = self.run(options, args)   file "/usr/lib/python2.7/dist-packages/pip/commands/install.py", line 328, in run     wb.build(autobuilding=true)   file "/usr/lib/python2.7/dist-packages/pip/wheel.py", line 748, in build     self.requirement_set.prepare_files(self.finder)   file "/usr/lib/python2.7/dist-packages/pip/req/req_set.py", line 360, in prepare_files     ignore_dependencies=self.ignore_dependencies))   file "/usr/lib/python2.7/dist-packages/pip/req/req_set.py", line 512, in _prepare_file     finder, self.upgrade, require_hashes)   file "/usr/lib/python2.7/dist-packages/pip/req/req_install.py", line 273, in populate_link     self.link = finder.find_requirement(self, upgrade)   file "/usr/lib/python2.7/dist-packages/pip/index.py", line 442, in find_requirement     all_candidates = self.find_all_candidates(req.name)   file "/usr/lib/python2.7/dist-packages/pip/index.py", line 400, in find_all_candidates     page in self._get_pages(url_locations, project_name):   file "/usr/lib/python2.7/dist-packages/pip/index.py", line 545, in _get_pages     page = self._get_page(location)   file "/usr/lib/python2.7/dist-packages/pip/index.py", line 648, in _get_page     return htmlpage.get_page(link, session=self.session)   file "/usr/lib/python2.7/dist-packages/pip/index.py", line 757, in get_page     "cache-control": "max-age=600",   file "/usr/share/python-wheels/requests-2.9.1-py2.py3-none-any.whl/requests/sessions.py", line 480, in     return self.request('get', url, **kwargs)   file "/usr/lib/python2.7/dist-packages/pip/download.py", line 378, in request     return super(pipsession, self).request(method, url, *args, **kwargs)   file "/usr/share/python-wheels/requests-2.9.1-py2.py3-none-any.whl/requests/sessions.py", line 468, in request     resp = self.send(prep, **send_kwargs)   file "/usr/share/python-wheels/requests-2.9.1-py2.py3-none-any.whl/requests/sessions.py", line 576, in send     r = adapter.send(request, **kwargs)   file "/usr/share/python-wheels/cachecontrol-0.11.5-py2.py3-none-any.whl/cachecontrol/adapter.py", line 46, in send     resp = super(cachecontroladapter, self).send(request, **kw)   file "/usr/share/python-wheels/requests-2.9.1-py2.py3-none-any.whl/requests/adapters.py", line 376, in send     timeout=timeout   file "/usr/share/python-wheels/urllib3-1.13.1-py2.py3-none-any.whl/urllib3/connectionpool.py", line 610, in urlopen     _stacktrace=sys.exc_info()[2])   file "/usr/share/python-wheels/urllib3-1.13.1-py2.py3-none-any.whl/urllib3/util/retry.py", line 228, in increment     total -= 1 typeerror: unsupported operand type(s) -=: 'retry' , 'int' 

what can solve problem? thank in advance.

this error may because behind proxy. try connect network without proxy (e.g. home), unset proxy environment variables: unset http_proxy, unset http_proxy, unset http_proxy, unset https_proxy run command again. pip install -u scikit-learn