Python & standard output redirection on ms-windows
Redirecting standard output of the Python script on ms-windows can cause strange crashes because of encoding differences.
Recently, I saw the following traceback when running the lamprop console application on ms-windows.
U:\>lamprop.py foo.lam >foo.txt Traceback (most recent call last): File "C:\_LocalData\Python3\lib\runpy.py", line 197, in _run_module_as_main return _run_code(code, main_globals, None, File "C:\_LocalData\Python3\lib\runpy.py", line 87, in _run_code exec(code, run_globals) File "__main__.py", line 97, in <module> File "__main__.py", line 93, in main File "C:\_LocalData\Python3\lib\encodings\cp1252.py", line 19, in encode return codecs.charmap_encode(input,self.errors,encoding_table) UnicodeEncodeError: 'charmap' codec can't encode character '\u03bd' in position 0: character maps to <undefined>
\u03bd is the greek letter ν.)
Since Python 3.6,
utf-8 is used as the encoding for
long as this is not redirected.
From the documentation:
On Windows, UTF-8 is used for the console device. Non-character devices such as disk files and pipes use the system locale encoding.
Suppose you have the following program;
import sys print(sys.stdout.encoding)
Normally, when you call this program from
cmd.exe, it will report
But, if you redirect its output to a file, that file will contain
So it you are trying to print a character that cannot be encoded in that
codepage, the abovementioned error occurs.
In the console version of lamprop, I added the following code to the program initialization.
if os.name == "nt": sys.stdout.reconfigure(encoding="utf-8")
The forces the output to
utf-8 even when it is redirected.
For comments, please send me an e-mail.
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