Latest tested version is 3.5.2 x64 you can get it here: https://www.python.org/ftp/python/3.5.2/python-3.5.2-amd64.exe
During the setup, install python for all users including pip and add Python path to windows env. variables.
After the installation, it should be located in c:\Program Files\Python35
.
Start windows console (cmd) as administrator. You can do it by creating a shortcut to cmd.exe and set the 'run as administrator' in its advanced settings
Then enter following command.
pip install requests PyQT5