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from inputformat import TextLineInput
from outputcollector import LineOutput
class MapperBase:
"""
Base class for every map tasks
Your map class should extend this base class
and override the map function
"""
def __init__(self):
"""
set the default input formatter and output collector
"""
self.inputformat = TextLineInput
self.outputcollector = LineOutput
def set_inputformat(self, format):
"""
set the input formatter for map task
@param format: the input formatter to parse the input
"""
self.inputformat = format
def set_outputcollector(self, collector):
"""
set the output collector for map task
@param collector: the ouput collector to collect output
"""
self.outputcollector = collector
def map(self, key, value):
"""
do map operation on each (key, value) pair
It is the only function needs to and
have to be implemented in your own class
It is a callback function that is called in C{call_map()} function
you should not call this function directly
the actual content of key and value is determined by the inputformat
@param key: key part in (key, value) pair
@type key: C{string}
@param value: value part in (key, value) pair
@type value: C{string}
"""
raise NotImplementedError('map() is not implemented in this class')
def call_map(self):
"""
driver function for map task, you should call this method
instead of the map method in main function
"""
data = self.inputformat.read_line()
for key, value in data:
self.map(key, value)
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