python string寫入二進制文件——直接wb形式open file，再write string即可

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You misunderstood what \xhh does in Python strings. Using \x notation in Python strings is just syntax to produce certain codepoints. You can use '\x61' to produce a string, or you can use 'a'; both are just two ways of saying give me a string with a character with hexadecimal value 61, e.g. the a ASCII character: >>> '\x61' 'a' >>> 'a' 'a' >>> 'a' == '\x61' True The \xhh syntax then, is not the value; there is no \ and no x and no 6 and 1 character in the final result. You should just write your string: somestring = 'abcd' with open("test.bin", "wb") as file: file.write(somestring) There is nothing magical about binary files; the only difference with a file opened in text mode is that a binary file will not automatically translate \n newlines to the line separator standard for your platform; e.g. on Windows writing \n produces \r\n instead. You certainly do not have to produce hexadecimal escapes to write binary data. On Python 3 strings are Unicode data and cannot just be written to a file without encoding, but on Python the str type is already encoded bytes. So on Python 3 you'd use: somestring = 'abcd' with open("test.bin", "wb") as file: file.write(somestring.encode('ascii')) or you'd use a byte string literal; b'abcd'.