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Enable MICROPY_PY_ARRAY_SLICE_ASSIGN on SAMD21 #193
Description
The following code:
a = bytearray(b'abc')
a[1:2] = b'123'
works just fine on MicroPython and CircuitPython on the ESP8266, but fails with
TypeError: 'bytearray' object does not support item assignment
on the M0 boards. This is the fastest way to copy a fragment of a byte array (since it uses memcpy in C), but since it doesn't work consistently on all ports, I can't use it in my libraries. It would be nice if all ports supported it.
Activity
dhalbert commentedon Sep 20, 2017
Turning on
MICROPY_PY_ARRAY_SLICE_ASSIGNtakes something like 384 to 576 bytes to include. I got different measurements based on trying to remove it from the Express build or add it to the non-Express build. It's a pretty Pythonic feature, and I think we could squeeze it in by lowering-finline-limitand/or seeing how big things are after the ASF4 port.gpshead commentedon Oct 30, 2017
I just noticed that this feature was missing on the non-express builds as I tried migrating some code to a smaller board. I'd love to see it there. If ultimately not, would it be possible to update the error message?
Currently it was something along the lines of
Error: bytearray index assignment not supported.(paraphrased, my uc isn't connected at the moment). This was confusing as this isn't index assignment, it is slice assignment. But even improving the error message would consume more string space...The workaround for a common case is a (presumably slow) manual loop:
Before:
After:
If you could even support just the case of slice assignment into a preallocated fixed buffer without reallocation/resizing that would be fine for my use case (I generally try to avoid reallocs)
dhalbert commentedon Oct 31, 2017
Current measurements say this costs 400 bytes. I guess I'd choose those over #384 (add
.decode) if I had to choose just one because it's more awkward without it. As with #384, we need to consider our storage budget in future releases.atmel-samd: Turn on slice assignment in all builds.