从int到Windows-1252的Python转换

Question

I am currently writing a program that reads data from a serial port adds some header information then writes this data to a .jpg file.

I require to write to the file in Windows-1252 encoding format, yes the method in which I construct the data and the header is in hexadecimal format.

I realised my problem when comparing the picture that should be written and what was actually written, and saw that DOULBE LOW 9 QUOTES were not written as quotes but rather as a zero.

The decimal code for that symbol is 132 (0x84) . If I use chr(0x84) I get the following error

UnicodeEncodeError: 'charmap' codec can't encode character \\x84 in position 0: character maps to

Which only makes sense if chr() was trying to map to Latin-1 codeset. I have tried to convert the int to a unicode but from my research chr is the only function that does this.

I have also tried to use the struct package in python.

import struct
a = 123;
b = struct.pack("c",a)
print(b)

I get the error

Traceback (most recent call last): File "python", line 3, in struct.error: char format requires a bytes object of length 1

Reading past questions, answers and documentation does get quite confusing as there is a mix of python2 and python3 answers mixed in with people converting to ascii (which obviously wouldn't work).

I am using Python 3.4.3 (the latest version) on a Windows 7 machine.

Answer 1

UnicodeEncodeError: 'charmap' codec can't encode character \\x84

\\x84 is the encoding of the lower quotes character in Windows-1252. This suggests your data is already encoded, and you should not try to encode it again. In a text string the quote should show up as "\„" . "\„" (the result of chr(132) ) is actually a control character .

You should have either bytes which you can decode to a string:

>>> b"\x84".decode('windows-1252')
'\u201e'

Or you should have a text string, which you can encode to a byte string

>>> "\u201e".encode('windows-1252')
b'\x84'

If you read data from somewhere you could use the struct module like this

# suppose we download some data:
data=b'*\x00\x00\x00abcde'

a, txt = struct.unpack("I5s", data)
print(txt.decode('windows-1252'))