列出top中的pid

 #!/usr/bin/env python

 import os
 import string

 #方法1：通过字符串的isdigits来判断
 #filelist = os.listdir('/proc')
 #
 #for pid in filelist:
 #    if pid.isdigit():
 #        print pid

 # 方法2：通过定义函数来判断
 def isNum(pid):
     for num in pid:
         if num in string.digits:
             continue
         else:
             return False
     return True

 for pid in os.listdir('/proc'):
     if isNum(pid):
         print pid