install 'pip' package for specific version of Python on Windows

Question

I have on my machine (windows 10) two versions of python: 3.5 2.7
I need to install a package using pip but I want the package on both.

My default version is 3.5.

I try to do this: pip2 install scikit-learn to install it on python 2.7 and I get this error:

Traceback (most recent call last):
  File "c:\python27\lib\runpy.py", line 162, in _run_module_as_main
    "__main__", fname, loader, pkg_name)
  File "c:\python27\lib\runpy.py", line 72, in _run_code
    exec code in run_globals
  File "C:\Python27\Scripts\pip2.exe\__main__.py", line 5, in <module>
  File "c:\python27\lib\site-packages\pip\__init__.py", line 13, in <module>
    from pip.commands import commands, get_similar_commands, get_summaries
  File "c:\python27\lib\site-packages\pip\commands\__init__.py", line 6, in <module>
    from pip.commands.bundle import BundleCommand
  File "c:\python27\lib\site-packages\pip\commands\bundle.py", line 5, in <module>
    from pip.commands.install import InstallCommand
  File "c:\python27\lib\site-packages\pip\commands\install.py", line 5, in <module>
    from pip.req import InstallRequirement, RequirementSet, parse_requirements
  File "c:\python27\lib\site-packages\pip\req\__init__.py", line 3, in <module>
    from .req_install import InstallRequirement
  File "c:\python27\lib\site-packages\pip\req\req_install.py", line 20, in <module>
    import pip.wheel
  File "c:\python27\lib\site-packages\pip\wheel.py", line 27, in <module>
    from pip.download import path_to_url, unpack_url
ImportError: cannot import name unpack_url

I also try this: python2.7 -m pip install scikit-learn or python27 -m pip install scikit-learn and I get this error:

python2.7 : The term 'python2.7' is not recognized as the name of a cmdlet,                  function, script file, or operable
program. Check the spelling of the name, or if a path was included, verify   that the path is correct and try agai
At line:1 char:1
+ python2.7 -m pip install scikit-learn
+ ~~~~~~~~~
  + CategoryInfo          : ObjectNotFound: (python2.7:String) [],           CommandNotFoundException
  + FullyQualifiedErrorId : CommandNotFoundException

I do have python 2.7 on C:\\Python27 .
What to do?

Answer 1

The safest and least frustrating way to go about this is to load independent copies of scikit learn into two virtual environments.

Install by:

$ pip install virtualenv

$ pip install virtualenvwrapper

Then

$ mkvirtualenv --python=<path to python> <name virtualenv>

To run it...

workon <name virtualenv>

Answer 2

On Windows you can use

for python2.x py -2 for python3.x py -3

so it would be

py -2 -m pip install scikit-learn
py -3 -m pip install scikit-learn

just try py --help for more info

Answer 3

Thanks allot for the answers, after some try&fail I find 2 different ways to figure it.
1. <PATH-FOR-PYTHON>\\scripts\\pip.exe install <package name>

2. py -2 -Em pip install scikit-learn for v3.5 py -3 -E -m pip install scikit-learn for v2.7