UnicodeDecodeError: 'gbk' codec can't decode byte

Question

运行 "Learn Python the Hard Way" 里的代码时出现的报错。代码：

1.  from sys import argv
2.  from os.path import exists                              
3.  
4.  script, from_file, to_file = argv
5.  
6.  print(f"Copying from {from_file} to {to_file}")
7.  
8.  # we could do these two on one line, how?
9.  in_file = open(from_file)
10. indata = in_file.read()
11.
12. print(f"The input file is {len(indata)} bytes long")
13.
14. print(f"Does the output file exsit? {exists(to_file)}")
15. print("Ready, hit RETURN to continue, CTRL-C to abort.")
16. input()
17. 
18. out_file = open(to_file, 'w')
19. out_file.write(indata)
20. 
21. print("Alright, all done.")
22. 
23. out_file.close()
24. in_file.close() 

照抄书本在 Terminal 上输入的命令：
$ echo "This is a test file." > test.txt
$ cat test.txt
This is a test file.
$ python ex17.py test.txt new_file.txt

下面是 Terminal 给的提示：
Copying from test.txt to new_file.txt
Traback ( most recent call last):
File "ex17.py", line 10, in
indata = in_file.read()
UnicodeDecodeError: 'gbk' codec can't decode byte 0xff in position 0: illegal multibyte sequence

尝试把 'gbk' 编码改为 'UTF-8':
9. in_file = open(from_file, 'r', encoding = 'UTF-8')

Terminal 给出的提示

Copying from test.txt to new_file.txt
Traceback (most recent call last):
File "ex17.py", line 10, in
indata = in_file.read()
File "C:\Python36\lib\codecs.py", line 321, in decode
(result, consumed) = self._buffer_decode(data, self.errors, final)
UnicodeDecodeError: 'utf-8' codec can't decode byte 0xff in position 0: invalid start byte

求解：是什么导致这个 Error ？以及如何解决？

Answer 1

UnicodeDecodeError 解码错误，请先确认源文件的编码是什么，然后用对应的编码解码。如果是gb2312，encoding='gb18030'试试，
如果编码确认无误，还出现解码错误，那么一定是文件出现无法解码的乱码。此时1：去除文件中的乱码 ； 2：以字节方式读入，然后decode时
传入errors='ignore'忽略解码错误即可。强调一下，一定要先确认编码无误。