Question

Is it !-\ (characters from 33=ord(‘!’) to 92=ord(‘\’)
and ‘.’ and ‘&’ in a set?

I think my interpretation is incorrect based on my test.

But python reference doesn’t say anything wrong with my interpretation.
http://docs.python.org/library/re.html

Answer 1

In short, r'[!-\.&]' is just a complicated form of writing r'[!-.]'.

It matches all characters with ord between 33 = ord('!') and 46 = ord('.'), i.e. any of the following:

!"#$%&\'()*+,-.

The escaping backslash before . is ignored in character classes; it is unnecessary (. matching all characters in a character class wouldn’t make any sense). Since the ampersand & is already in the character class, it is superfluous as well.