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| -rw-r--r-- | Misc/FAQ | 29 |
1 files changed, 10 insertions, 19 deletions
@@ -1295,25 +1295,16 @@ to sys.stderr when this happens. 4.18. Q. How do I change the shell environment for programs called using os.popen() or os.system()? Changing os.environ doesn't work. -A. Modifying the environment passed to subshells was left out of the -interpreter because there seemed to be no well-established portable -way to do it (in particular, some systems, have putenv(), others have -setenv(), and some have none at all). - -However if all you want is to pass environment variables to the -commands run by os.system() or os.popen(), there's a simple solution: -prefix the command string with a couple of variable assignments and -export statements. The following would be universal for popen: - - import os - from commands import mkarg # nifty routine to add shell quoting - def epopen(cmd, mode, env = {}): - # env is a dictionary of environment variables - prefix = '' - for key, value in env.items(): - prefix = prefix + '%s=%s\n' % (key, mkarg(value)[1:]) - prefix = prefix + 'export %s\n' % key - return os.popen(prefix + cmd, mode) +A. You must be using either a version of python before 1.4, or on a +(rare) system that doesn't have the putenv() library function. + +Before Python 1.4, modifying the environment passed to subshells was +left out of the interpreter because there seemed to be no +well-established portable way to do it (in particular, some systems, +have putenv(), others have setenv(), and some have none at all). As +of Python 1.4, almost all Unix systems *do* have putenv(), and so does +the Win32 API, and thus the os module was modified so that changes to +os.environ are trapped and the corresponding putenv() call is made. 4.19. Q. What is a class? |