python中的ReduceByKey

Python中是否有一个函数与Spark（PySpark）中的

reduceByKey

完全相同：

例如：

a = [(1, ['a']),
     (1, ['b']),   
     (2, ['c']),   
     (2, ['d']),   
     (3, ['e'])]

到

---

据我所知没有。但是自己写一本很容易

from collections import OrderedDict

def reduce_by_key(ls):
    d = OrderedDict()
    for key, sublist in ls:
        d.setdefault(key, []).extend(sublist)
    return list(d.items())

---

如果不需要保留顺序，可以使用常规的

dict

。

没有。也许你能得到的最接近的东西是，尽管它有不同的语义（以流方式应用，所以它不假设关联性或交换性）。它还可以减少过完整的对象并返回字典：

list(reduceby(first, lambda x, y: (first(x), second(x) + second(y)), a).values())
## [(1, ['a', 'b']), (2, ['c', 'd']), (3, ['e'])]

from collections import OrderedDict

def reduce_by_key(ls):
    d = OrderedDict()
    for key, sublist in ls:
        d.setdefault(key, []).extend(sublist)
    return list(d.items())

list(reduceby(first, lambda x, y: (first(x), second(x) + second(y)), a).values())
## [(1, ['a', 'b']), (2, ['c', 'd']), (3, ['e'])]