我想用 mrjob 声明一个映射器函数。因为我的映射器函数需要引用一些常量来进行一些计算，所以我决定将这些常量放入映射器中的 Key 中(还有其他方法吗？)。我在 this site 上阅读了 mrjob 教程但所有的例子都忽略了这个键。例如:
class MRWordFrequencyCount(MRJob):
def mapper(self, _, line):
yield "chars", len(line)
yield "words", len(line.split())
yield "lines", 1
def reducer(self, key, values):
yield key, sum(values)
基本上，我想要这样的东西:
def mapper(self, (constant1,constant2,constant3,constant4,constant5), line):
My calculation goes here
请建议我该怎么做。谢谢
最佳答案
您可以在 __init__ 中设置常量
from mrjob.job import MRJob
class MRWordFrequencyCount(MRJob):
def mapper(self, key, line):
yield "chars", len(line)
yield "words", len(line.split())
yield "lines", 1
yield "Constant",self.constant
def reducer(self, key, values):
yield key, sum(values)
def __init__(self,*args,**kwargs):
super(MRWordFrequencyCount, self).__init__(*args, **kwargs)
self.constant = 10
if __name__ == '__main__':
MRWordFrequencyCount.run()
输出:
"Constant" 10
"chars" 12
"lines" 1
"words" 2
或者，您可以使用RawProtocol
from mrjob.job import MRJob
import mrjob
class MRWordFrequencyCount(MRJob):
INPUT_PROTOCOL = mrjob.protocol.RawProtocol
def mapper(self, key, line):
yield "constant", key
yield "chars", len(line)
yield "words", len(line.split())
yield "lines", 1
def reducer(self, key, values):
if str(key) != "constant":
yield key, sum(values)
else:
yield "constant",list(values)
if __name__ == '__main__':
MRWordFrequencyCount.run()
如果输入是:
constant1,constant2,constant3 The quick brown fox jumps over the lazy dog
输出:
"chars" 43
"constant" ["constant1,constant2,constant3"]
"lines" 1
"words" 9
关于python - 声明 mrjob 映射器而不忽略 key，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/33745977/