On: What's Coming in Python 3.8

[chrisseaton]

It can be reduced into two simpler lines can’t it, both of which could be understood in isolation.

[baq → chrisseaton]

understanding lines in isolation is precisely besides the point here, because the code pattern has to be understood as a whole.

[chrisseaton → baq]

I don’t see why. ‘Assign x’ and ‘is x truthy’ can be understood separately. Worry about what x is being assigned. Then worry about whether its value is truthy.

[baq → chrisseaton]

like I said, the whole pattern is more than two lines. the pattern is actually assign-test-fallback-test-fallback-test-etc.

to quote the PEP:

  reductor = dispatch_table.get(cls)
  if reductor:
      rv = reductor(x)
  else:
      reductor = getattr(x, "__reduce_ex__", None)
      if reductor:
          rv = reductor(4)
      else:
          reductor = getattr(x, "__reduce__", None)
          if reductor:
              rv = reductor()
          else:
              raise Error(
                  "un(deep)copyable object of type %s" % cls)

becomes:

  if reductor := dispatch_table.get(cls):
      rv = reductor(x)
  elif reductor := getattr(x, "__reduce_ex__", None):
      rv = reductor(4)
  elif reductor := getattr(x, "__reduce__", None):
      rv = reductor()
  else:
      raise Error("un(deep)copyable object of type %s" % cls)