Chapter 3. Python Libraries

3.1. Overview

The Python libraries (versions 2 and 3) for WebMapReduce expect the mapper and reducer to be defined by the following functions:

function mapper(key, value): Map the input pair composed of key and value. Both arguments are strings.
function reducer(key, values): Reduce the intermediate values associated with key. values is an iterator that yields string values, and key is a string.

Output is given through the Wmr.emit(key, value) function.