How to run SVN commands from a python script?
Try pysvn
Gives you great access as far as i've tested it.Here's some examples: http://pysvn.tigris.org/docs/pysvn_prog_guide.html
The reason for why i'm saying as far as i've tested it is because i've moved over to Git.. but if i recall pysvn is (the only and) the best library for svn.
Take a look into the python xonsh module: http://xon.sh/tutorial.html
It can call shell commands plus piping and output redirection with close touch to the python native code (nested) without need to play with python communicate bullshet and escape characters around.
Examples:
env | uniq | sort | grep PATH
COMMAND1 e>o < input.txt | COMMAND2 > output.txt e>> errors.txt
echo "my home is $HOME"
echo @(7+3)