Exception being thrown in spi.py with new Python 3.9

[gcs278]

• Platform/operating system (i.e. Raspberry Pi with Raspbian operating system, Windows 32-bit, Windows 64-bit, Mac OSX 64-bit, etc.): Raspberry Pi with HassIO

• Python version (run python -version or python3 -version): Python 3.9.0

• Error message you are receiving, including any Python exception traces:

  
  File "/usr/local/lib/python3.9/site-packages/adafruit_mcp3xxx/analog_in.py", line 78, in voltage
  return (self.value * self._mcp.reference_voltage) / 65535
  File "/usr/local/lib/python3.9/site-packages/adafruit_mcp3xxx/analog_in.py", line 70, in value
  self._mcp.read(self._pin_setting, is_differential=self.is_differential) << 6
  File "/usr/local/lib/python3.9/site-packages/adafruit_mcp3xxx/mcp3xxx.py", line 99, in read
  spi.write_readinto(self._out_buf, self._in_buf)
  File "/usr/local/lib/python3.9/site-packages/busio.py", line 310, in write_readinto
  return self._spi.write_readinto(
  File "/usr/local/lib/python3.9/site-packages/adafruit_blinka/microcontroller/generic_linux/spi.py", line 130, in write_readinto
  data = self._spi.transfer(list(buffer_out[out_start : out_end + 1]))
  File "/usr/local/lib/python3.9/site-packages/Adafruit_PureIO/spi.py", line 411, in transfer
  data = array.array("B", data).tostring()
  AttributeError: 'array.array' object has no attribute 'tostring'

- List the steps to reproduce the problem below (if possible attach code or commands
  to run):
1. Install python 3.9
2. `pip3 install adafruit-circuitpython-mcp3xxx` (this is what uses spi.py and why I'm here)
3.  Write the code (this is a snippet from my project, may not be 100% right)

import adafruit_mcp3xxx.mcp3008 as MCP from adafruit_mcp3xxx.analog_in import AnalogIn adc1 = MCP.MCP3008(spi, chip_select) pin1 = AnalogIn(adc1, MCP.P0) pin1.voltage

File "/usr/local/lib/python3.9/site-packages/adafruit_mcp3xxx/analog_in.py", line 78, in voltage return (self.value * self._mcp.reference_voltage) / 65535 File "/usr/local/lib/python3.9/site-packages/adafruit_mcp3xxx/analog_in.py", line 70, in value self._mcp.read(self._pin_setting, is_differential=self.is_differential) << 6 File "/usr/local/lib/python3.9/site-packages/adafruit_mcp3xxx/mcp3xxx.py", line 99, in read spi.write_readinto(self._out_buf, self._in_buf) File "/usr/local/lib/python3.9/site-packages/busio.py", line 310, in write_readinto return self._spi.write_readinto( File "/usr/local/lib/python3.9/site-packages/adafruit_blinka/microcontroller/generic_linux/spi.py", line 130, in write_readinto data = self._spi.transfer(list(buffer_out[out_start : out_end + 1])) File "/usr/local/lib/python3.9/site-packages/Adafruit_PureIO/spi.py", line 411, in transfer data = array.array("B", data).tostring() AttributeError: 'array.array' object has no attribute 'tostring'

EDIT: 
Oh and I've been running with adafruit-circuitpython-mcp3xxx for the last 5 months, no problems, until I went to rebuild my docker container (and got a new python update). I nearly got the soldering iron out again until I saw the exception.

[gcs278]

Wow that was incredibly fast thanks!! On a Friday evening too.

[ladyada]

we may be werewolves