Cannot overload float()

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Cannot overload float()

Post by ProudPagan » Wed May 22, 2019 2:49 am


I am redefining int() and float() for my number-like class (simplified floatoverload class below), but I get a TypeError
when trying to use float(). I am returning a floating point number from __float__ ( ).

int( ) works fine.

Any pointers on what might would be much appreciated. I am using:
MicroPython v1.10-278-g673e154df-dirty on 2019-04-16; win32 version

EDIT: This code works with CPython (tried using 3.6.8)

Code: Select all

class floatoverload (object):

	def __init__ (self):

	def __float__ (self):
		return 99.9

	def __int__ (self):
		return 999

Code: Select all

>>> from floatoverload import floatoverload
>>> int(floatoverload())
>>> float(floatoverload())
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: can't convert floatoverload to float

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Re: Cannot overload float()

Post by jimmo » Wed May 22, 2019 2:58 am

Unfortunately__float__ is not implemented in MicroPython. If you're interested in the implementation of __int__ search for MP_UNARY_OP_INT in the repo.

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Re: Cannot overload float()

Post by pythoncoder » Wed May 22, 2019 8:28 am

In general subclassing built-in types is not supported by MicroPython. See this doc. A solution which works in some cases is to use composition and to simulate inheritance.
Peter Hinch

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