pip_auto_update.bat

@echo off

rem Define a (local) name for the temporary file
setlocal
set temp="tmp.txt"

rem Copy the list of outdated modules to a text file
call pip list --outdated > %temp%

rem Process the text file to only contain module names
call python -c "m='\n'.join(map(lambda x: x.split()[0], open('%temp%', 'r').readlines())); open('%temp%', 'w').write(m)"

rem Pipe the file back to pip and install the modules
call pip install --upgrade -r %temp%

rem Delete the text file
del %temp%

rem Free the now-unnecessary variable for the filename
endlocal

This gist basically uses pip's ability to list whatever libraries are out-of-date, saves this to a file, modifies the file to only contain the module names, uses this new file to install the up-to-date versions and then finally removes the temporary file.

Even if the file wouldn't be deleted, the script doesn't break. That being said, it will only work as long as pip's output syntax doesn't change drastically.

Also, never use Python one-liners like this one. My script is just an example.