Python中pipe和>>是什么？[副本]

Question

lines = p | 'read' >> ReadFromText(known_args.input)

  # Count the occurrences of each word.
  def count_ones(word_ones):
    (word, ones) = word_ones
    return (word, sum(ones))

  counts = (lines
            | 'split' >> (beam.ParDo(WordExtractingDoFn())
                          .with_output_types(unicode))
            | 'pair_with_one' >> beam.Map(lambda x: (x, 1))
            | 'group' >> beam.GroupByKey()
            | 'count' >> beam.Map(count_ones))

来自:https://github.com/apache/beam/blob/master/sdks/python/apache_beam/examples/wordcount.py#l92

Python中和>的语法和用法是什么？

Answer 1

默认情况下，代表逻辑或位或运算符，>代表右移，但幸运的是，您可以在Python中重载运算符。因此，为了对和>>进行自定义，只需在类__or__和__rshift__中重载以下两个dunder（magic）方法：

class A():
    def __or__(self):
        pass
    def __rshift__(self):
        pass

我建议您阅读更多关于Python数据模型的内容。

现在看一下Beam Python SDK，__or__在PTransform类中重载：

  def __or__(self, right):
    """Used to compose PTransforms, e.g., ptransform1 | ptransform2."""
    if isinstance(right, PTransform):
      return _ChainedPTransform(self, right)
    return NotImplemented