Convert object 'bytes' to string
I tried to find a solution but still stuck with it. I want to use PyVisa to control a function generator. I have waveform
which is a list of values between 0
and 16382
Then I have to prepare it such that each point waveform
takes 2 bytes. The value is in big-endian, MSB-first format and is direct binary. So I do binwaveform = pack('>'+'h'*len(waveform), *waveform)
And then when I try to write it to the instrument with AFG.write('trace ememory, '+ header + binwaveform)
, I get the error:
File ".\afg3000.py", line 97, in <module>
AFG.write('trace ememory, '+ header + binwaveform)
TypeError: Can't convert 'bytes' object to str implicitly
I tried to solve it with AFG.write('trace ememory, '+ header + binwaveform.decode())
, but it looks like it tries to use ASCII characters by default, which is wrong for some values:UnicodeDecodeError: 'utf-8' codec can't decode byte 0x80 in position 52787: invalid start byte
Could you help me?
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binwaveform
is a packed array of integer bytes. For example:
struct.pack('<h', 4545)
b'\xc1\x11'
You cannot print it as it doesn't make any sense to your terminal. In the above example,
0xC1
ASCII and UTF-8 are invalid.
When you add a byte string to a regular string ( trace ememory, '+ header + binwaveform
), Python wants to convert it to readable text, but doesn't know how.
The decoding assumes that the text is not.
Your best bet is to print the hexadecimal representation:
import codecs binwaveform_hex = codecs.encode(binwaveform, 'hex') binwaveform_hex_str = str(binwaveform_hex) AFG.write('trace ememory, '+ header + binwaveform_hex_str)
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