On Fri, 22 May 2009 03:42:18 +0100, walterbyrd <walterb...@iname.com>
wrote:
I guess I am confused about when when escape characters are are
interpersonal as escape characters, and escape characters are not
treated as escape characters.
No, you're confused about the number of entirely different things
that are interpreting a string, and the difference between a string
literal and a string object.
Sometimes escape characters in regular strings are treated as escape
characters, sometimes not. Same seems to go for raw strings. So how do
I know?
IMO: '\' characters in raw strings should not be given any special
meaning. That would also solve the common problem of r'c:\whatever\'
not working in python. But I digress.
Escaping the delimiting quote is the *one* time backslashes have a
special meaning in raw string literals.
To me this does not seem right. r'\n' should not equal '\n'
And it doesn't. Let me explain. No, that would take too long,
let me summarise. :-)
s = 'x\nx'
`s` is a string object containing the character 'x', a newline, and 'x'.
a = re.sub('\n', 'x', s)
This calls re.sub with a pattern string object that contains a single
newline character. Since this character has no special meaning to the
sub function it faithfully searches `s` for newlines, and, finding one,
replaces it with an 'x' character.
a = re.sub(r'\n', 'x', s)
This calls re.sub with a pattern string object that contains two
characters, a backslash followed by an 'n'. This combination *does*
have a special meaning to the sub function, which does it's own
translation of the pattern into a single newline character. Then,
as before, it spots the newline in `s` and replaces it with an 'x'.
Note, however, that the string object created by the raw string literal
was *two* characters long. It's re.sub (in common with the rest of the
re module functions) that chooses to interpret the backslash specially.
--
Rhodri James *-* Wildebeeste Herder to the Masses
--
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