What's the point of chr(128) .. chr(255) in Python?

Question

Edit: I'm talking about behavior in Python 2.7.

The chr function converts integers between 0 and 127 into the ASCII characters. E.g.

>>> chr(65)
'A'

I get how this is useful in certain situations and I understand why it covers 0..127, the 7-bit ASCII range.

The function also takes arguments from 128..255. For these numbers, it simply returns the hexadecimal representation of the argument. In this range, different bytes mean different things depending on which part of the ISO-8859 standard is used.

I'd understand if chr took another argument, e.g.

>>> chr(228, encoding='iso-8859-1') # hypothetical
'ä'

However, there is no such option:

chr(i) -> character

Return a string of one character with ordinal i; 0 <= i < 256.

My questions is: What is the point of raising ValueError for i > 255 instead of i > 127? All the function does for 128 <= i < 256 is return hex values?

Answer 1

In Python 2.x, a str is a sequence of bytes, so chr() returns a string of one byte and accepts values in the range 0-255, as this is the range that can be represented by a byte. When you print the repr() of a string with a byte in the range 128-255, the character is printed in escape format because there is no standard way to represent such characters (ASCII defines only 0-127). You can convert it to Unicode using unicode() however, and specify the source encoding:

unicode(chr(200), encoding="latin1")

In Python 3.x, str is a sequence of Unicode characters and chr() takes a much larger range. Bytes are handled by the bytes type.