have a bit of code that works in Python 3.5 but not micropython:

d = {1:"hello", 2:"world"}
len(d)
len(d.items())

In Py3.5 and 2.7, both len(d) and len(d.items()) return 2
In micropython, len(d) is 2 but len(d.items()) throws:

len(d.items())
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: object of type 'dict_view' has no len()

Note that len(d.items()) == len(d.keys()) == len(d.values()) == len(d) should be true for consistency.

I don't think the version matters but I am running a variant of 1.20.0 on an STM32 L4:

MicroPython 724865b19-dirty on 2023-09-05; NUCLEO-L4A6ZG with STM32L4A6ZG
Type "help()" for more information.