在python 2.4中，如何使用csh而不是bash执行外部命令？

Without using the new 2.6 subprocess module, how can I get either os.popen or os.system to execute my commands using the tcsh instead of bash? I need to source some scripts which are written in tcsh before executing some other commands and I need to do this within python2.4.Without using the new 2.6 subprocess module, ho