int() doesn't seem to work.

[cooper]

Hi,

I have some code which reads in messages from the serial port and shoves it into a buffer:

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buffer = buffer[:-2]
br = buffer.split("=")[1]
brightness = int(br)
print(brightness)

Yet when I try to convert the string to an int, i get:

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ValueError: invalid syntax for integer with base 10: '0'

The thing is, when I type that code into REPL, substituting buffer with "br=057", it works fine...

I'm probably missing something very obvious here but I cant seem to figure it out, any help would be appreciated.

Thanks

[pythoncoder]

The serial port returns a bytes object, whereas when you type into the REPL you create a Unicode string. To replicate the behaviour of the serial port you need to do this:

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buffer =b"br=057" # Creates a bytes object
buffer = buffer.decode('UTF-8') # convert to string
buffer = buffer[:-2]
br = buffer.split("=")[1]
int(br)

[cooper]

Thank you for your reply, perhaps it would help if i pasted the entire section:

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	while 1:
		if rs485.any():
			val = str(rs485.read(1).decode("ascii"))
			if ord(val) == 0x02:
				print(buffer)

				if "br=" in buffer or "tr=" in buffer:
					buffer = buffer[:-2]
					br = buffer.split("=")[1]
					brightness = int(br)
					print(brightness)

				buffer = ""

			else:
				buffer += val

I am decoding my bytes as ascii as opposed to unicode, I have even stuck in a print(type(buffer)) which returns

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05br=552
<class 'str'>

So it seems I am dealing with a string but my issue persists.

[dhylands]

buffer = buffer[:-2] strips the last 2 bytes off the line. Is that what you were intending?

Can you create a standalone example that doesn't need the UART to demonstrate the problem?

I tried this:

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>>> buffer = '05br=552'
>>> if "br=" in buffer or "tr=" in buffer:
...     buffer = buffer[:-2]
...     br = buffer.split("=")[1]
...     brightness = int(br)
...     print(brightness)
... 
5

which seems to be what I would expect.

[cooper]

Yes, the last two bytes are checksum bytes, which i dont intend to use at all.

The standalone stuff works perfectly fine, it is only when I use the data from the UART where it goes funny. Which is rather annoying as that is the only part holding back the demo!

Edit: OK, so I tried the same script on my PC with a USB to Serial converter and got this error:

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ValueError05br=100F6
: invalid literal for int() with base 10: '100\x03'

I had totally forgotten that there was an ETX byte in the string, which was causing me headache, as it was a non printable character it didn't show up.

Thank you for your assistance.