Strings Are Unicode

At the beginning of this section, we defined strings as immutable collections of Unicode characters. This actually makes things very complicated at times, because Unicode isn’t a storage format. If we get a string of bytes from a file or a socket, for example, they won’t be in Unicode. They will, in fact, be the built-in type bytes. Bytes are the basic storage format in computing. They represent 8 bits, usually described as an integer between 0 and 255, or a hexadecimal equivalent between 0x00 and 0xFF. Bytes don’t represent anything specific; a sequence of bytes may store characters of an encoded string, or pixels in an image, or represent an integer, or part of a floating-point value.

If we print a bytes object, Python uses a canonical display that’s reasonably compact. Any of the individual byte values that map to ASCII characters are displayed as characters, while non-character ASCII bytes are printed as escapes, either a one- character escape like \n or a hex code like \x1b. We may find it odd that a byte, represented as an integer, can map to an ASCII character. But the old ASCII code defined Latin letters for many different byte values. In ASCII the character a is represented by the same byte as the integer 97, which is the hexadecimal number 0x61. All of these are an interpretation of the binary pattern 0b1100001.