Initialization at Start of an R Session on Windows

The following explains how to setup an .Renviron and .Rprofile file at Windows with a special focus on PythonInR, a general documentation can be found here

Where is my HOME Folder?

The home directory is normally set to C:\Users\username\Documents and can be obtained by typing

Sys.getenv("R_USER")

Set Persistent Environment Variables

To set persistent environment variables on Windows the file .Renviron can be utilized. Just create a file with the name .Renviron in your home folder. NOTE: Renaming a existing file to .Renviron didn't work for me since Windows complained that I should enter a file name. But saving a file from a text editor as .Renviron did work.

If your python.exe file is located at C:/Python27/python.exe you should put the following into your .Renviron file.

PYTHON_EXE=C:/Python27/python.exe

Or for those who prefer to not leave their R terminal.

envFile <- file.path(Sys.getenv("R_USER"), ".Renviron")
x <- if (file.exists(envFile)) readLines(envFile) else character()
x <- unique(c(x, 'PYTHON_EXE=C:/Python27/python.exe'))
writeLines(x, envFile)

Setup .Rprofile

.Rprofile can be used to execute R code at the startup. Therefore it can also be used to set environment variables. Just put

Sys.setenv(PYTHON_EXE="C:/Python27/python.exe")