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