How to choose Python if they have 2 versions?

Was Python 2.7, put another, 3.5 , trying to install Django on 3.5 (2.7. Django already is), but displays this error, how can I change the version of Python for further operation of the OS?

C:\Python35>pip install Django==1.10.3
Collecting Django==1.10.3
Exception:
Traceback (most recent call last):
File "c:\python27\lib\site-packages\pip\basecommand.py", line 211, in main
status = self.run(options, args)
File "c:\python27\lib\site-packages\pip\commands\install.py", line 294, in run
requirement_set.prepare_files(finder)
File "c:\python27\lib\site-packages\pip\req\req_set.py", line 334, in prepare_files
functools.partial(self._prepare_file, finder))
File "c:\python27\lib\site-packages\pip\req\req_set.py", line 321, in _walk_req_to_install
more_reqs = handler(req_to_install)
File "c:\python27\lib\site-packages\pip\req\req_set.py", line 461, in _prepare_file
req_to_install.populate_link(finder, self.upgrade)
File "c:\python27\lib\site-packages\pip\req\req_install.py", line 250, in populate_link
self.link = finder.find_requirement(self, upgrade)
File "c:\python27\lib\site-packages\pip\index.py", line 486, in find_requirement
all_versions = self._find_all_versions(req.name)
File "c:\python27\lib\site-packages\pip\index.py", line 404, in _find_all_versions
index_locations = self._get_index_urls_locations(project_name)
File "c:\python27\lib\site-packages\pip\index.py", line 378, in _get_index_urls_locations
page = self._get_page(main_index_url)
File "c:\python27\lib\site-packages\pip\index.py", line 818, in _get_page
return HTMLPage.get_page(link, session=self.session)
File "c:\python27\lib\site-packages\pip\index.py", line 928, in get_page
"Cache-Control": "max-age=600",
File "c:\python27\lib\site-packages\pip\_vendor\requests\sessions.py", line 477, in get
return self.request('GET', url, **kwargs)
File "c:\python27\lib\site-packages\pip\download.py", line 373, in request
return super(PipSession, self).request(method, url, *args, **kwargs)
File "c:\python27\lib\site-packages\pip\_vendor\requests\sessions.py", line 465, in request
resp = self.send(prep, **send_kwargs)
File "c:\python27\lib\site-packages\pip\_vendor\requests\sessions.py", line 605, in send
r.content
File "c:\python27\lib\site-packages\pip\_vendor\requests\models.py", line 750, in content
self._content = bytes().join(self.iter_content(CONTENT_CHUNK_SIZE)) or bytes()
File "c:\python27\lib\site-packages\pip\_vendor\requests\models.py", line 673, in generate
for chunk in self.raw.stream(chunk_size, decode_content=True):
File "c:\python27\lib\site-packages\pip\_vendor\requests\packages\urllib3\response.py", line 307, in stream
data = self.read(amt=amt, decode_content=decode_content)
File "c:\python27\lib\site-packages\pip\_vendor\requests\packages\urllib3\response.py", line 243, in read
data = self._fp.read(amt)
File "c:\python27\lib\site-packages\pip\_vendor\cachecontrol\filewrapper.py", line 54, in read
self.__callback(self.__buf.getvalue())
File "c:\python27\lib\site-packages\pip\_vendor\cachecontrol\controller.py", line 244, in cache_response
self.serializer.dumps(request, response, body=body)
File "c:\python27\lib\site-packages\pip\download.py", line 276, in set
return super(SafeFileCache, self).set(*args, **kwargs)
File "c:\python27\lib\site-packages\pip\_vendor\cachecontrol\caches\file_cache.py", line 99, in set
with self.lock_class(name) as lock:
File "c:\python27\lib\site-packages\pip\_vendor\lockfile\mkdirlockfile.py", line 18, in __init__
LockBase.__init__(self, path, threaded, timeout)
File "c:\python27\lib\site-packages\pip\_vendor\lockfile\__init__.py", line 189, in __init__
hash(self.path)))
File "c:\python27\lib\ntpath.py", line 85, in join
result_path = result_path + p_path
UnicodeDecodeError: 'ascii' codec can't decode byte 0xec in position 0: ordinal not in range(128)

C:\Python35>
July 2nd 19 at 18:16
3 answers
July 2nd 19 at 18:18
Solution
First, to call pip that Python, in which the desired setting. For example, C:\Python35\Scripts\pip install Django==1.10.3

Secondly, do C:\Python35\python -m pip install --upgrade pip Error should go away.
July 2nd 19 at 18:20
I would advise to switch to virtualenv . For example , at least will not "spoil" in the "system" installation packages for different projects. Plus it is more convenient to generate a list of dependencies for each project.
July 2nd 19 at 18:22
With the latest windowapi pythons came to the team-starter py (pyw for guelich programs). Respectively called
for the last 3rd
py -3-m pip install
for the second
py -2 -m pip install
etc., see py --help
By the way, the last of the pythons, probably due to the appearance of this command, no longer by default be placed in the root of the C: drive.

Find more questions by tags Python