Eric V. Smith added the comment: Where is plink.exe? If it's not in cwd (c:\python33\workspace), note that the documentation for cwd says: "If cwd is not None, the function changes the working directory to cwd before executing the child. In particular, the function looks for executable (or for the first item in args) relative to cwd if the executable path is a relative path." Although confusingly, the 2.7 documentation says: "If cwd is not None, the child’s current directory will be changed to cwd before it is executed. Note that this directory is not considered when searching the executable, so you can’t specify the program’s path relative to cwd." ---------- _______________________________________ Python tracker <report@bugs.python.org> <http://bugs.python.org/issue20927> _______________________________________