将 hadoop 流与 python 组合器一起使用时失败

我尝试使用 python 的 hadoop 流来计算输入键的平均值。以下是mapper、combiner和reducer的代码：

#mapper:

import sys

def map(argv):
    line = sys.stdin.readline()
    try:
        while line:
            word, num = line.split()
            num = int(num)
            print word+'\t'+str(num)
            line = sys.stdin.readline()
    except Exception, ex:
        print 'mapper ex:'+str(ex)
        return None

if __name__ == "__main__":
    map(sys.argv)

#combiner
import sys

def combine(argv):
    line = sys.stdin.readline()
    cur_word = ''
    cur_num = 0
    cur_times = 0
    try:
        while line:
            word, num = line.split('\t')

            if word != cur_word:
                if cur_word != '':
                    print cur_word+'\t'+str(cur_num)+'\t'+str(cur_times)
                cur_word = word
                cur_num = 0
                cur_times = 0
            cur_num += int(num)
            cur_times += 1
            line = sys.stdin.readline()
        print cur_word+'\t'+str(cur_num)+'\t'+str(cur_times)

    except Exception, ex:
        print 'except:{0}'.format(ex)
        return None

if __name__ == "__main__":
    combine(sys.argv)


#reducer

import sys

def reduce(argv):
    line = sys.stdin.readline()
    cur_word = ''
    cur_num = 0
    cur_times = 0
    try:
        while line:
            word, num, times = line.split('\t')
            if word != cur_word:
                if cur_word != '':
                    if cur_times != 0:
                        avr = cur_num / cur_times
                        print cur_word+'\t'+str(cur_num)+'\t'+str(cur_times)+'\t'+str(avr)
                    else:
                        print cur_word+'\t'+str(cur_num)+'\t'+str(cur_times)+'\t'+'0'
                cur_word = word
                cur_num = 0
                cur_times = 0
            cur_num += int(num)
            cur_times += int(times)

            line = sys.stdin.readline()

        if cur_times != 0:
            avr = cur_num / cur_times
            print cur_word+'\t'+str(cur_num)+'\t'+str(cur_times)+'\t'+str(avr)
        else:
            print cur_word+'\t'+str(cur_num)+'\t'+str(cur_times)+'\t'+'0'

    except Exception, ex:
        print 'except:{0}'.format(ex)
        return None

if __name__ == "__main__":
    reduce(sys.argv)

这似乎是一个简单的映射-组合-归约过程，不是吗？但reduce每次都会失败。 但是，如果我不使用combiner，而是使用combiner.py作为reducer，它就可以工作。

有人会感激任何帮助吗，非常感谢。