You can obtain Python 3 installers for Windows from the python.org website by performing the following steps:
- Go to http://www.python.org/downloads/windows.
- Select the latest Python 3 release. At the time of writing, the latest version is 3.6.4, with 3.7 promising to be out by publishing time.
- Under the Files section, select the Windows executable installer appropriate to your system's architecture (x86 for 32-bit Windows, x86_64 for 64-bit Windows).
- Launch the downloaded installer.
- Click on Customize installation. Make sure the tcl/tk and IDLE option is checked (it should be by default).
- Continue through the installer with all defaults.