this call opens file with whatever program is listed in the windows registry for the file' type--as though its icon has been clicked with the mouse cursoros startfile("webpage html"os startfile("document doc"os startfile("myscript py"open file in your web browser open file in microsoft word run file with python the os popen call does not generally block its caller (by definitionthe caller must be able to read or write the file object returnedbut callers may still occasionally become blocked under both windows and linux if the pipe object is closed-- when garbage is collected--before the spawned program exits or the pipe is read exhaustively ( with its read(methodas we will see later in this part of the bookthe unix os fork/exec and windows os spawnv calls can also be used to run parallel programs without blocking because the os module' system and popen callsas well as the subprocess modulealso fall under the category of program launchersstream redirectorsand cross-process communication devicesthey will show up again in the following so we'll defer further details for the time being if you're looking for more details right awaybe sure to see the stream redirection section in the next and the directory listings section in other os module exports that' as much of tour around os as we have space for here since most other os module tools are even more difficult to appreciate outside the context of larger application topicswe'll postpone deeper look at them until later but to let you sample the flavor of this modulehere is quick preview for reference among the os module' other weapons are theseos environ fetches and sets shell environment variables os fork spawns new child process on unix-like systems os pipe communicates between programs os execlp starts new programs os spawnv starts new programs with lower-level control os open opens low-level descriptor-based file os mkdir creates new directory system tools