os.path.isfile

[Chris Angelico]

On Mon, Feb 13, 2017 at 10:56 AM, Erik <python at lucidity.plus.com> wrote:
> Actually, while contriving those examples, I noticed that sometimes when
> using string literal concatenation, the 'rawness' of the initial string is
> sometimes applied to the following string and sometimes not:
>
>>>> "hello \the" r"worl\d"
> 'hello \theworl\\d'
>
> Makes sense - the initial string is not raw, the concatenated string is.
>
>>>> r"hello \the" "worl\d"
> 'hello \\theworl\\d'
>
> Slightly surprising. The concatenated string adopts the initial string's
> 'rawness'.
>
>>>> "hello \the" r"worl\d" "\t"
> 'hello \theworl\\d\t'
>
> The initial string is not raw, the following string is. The string following
> _that_ becomes raw too.
>
>>>> r"hello \the" "worl\d" "\t"
> 'hello \\theworl\\d\t'
>
> The initial string is raw. The following string adopts that (same as the
> second example), but the _next_ string does not!
>
>>>> r"hello \the" "worl\d" r"\t"
> 'hello \\theworl\\d\\t'
>
> ... and this example is the same as before, but makes the third string "raw"
> again by explicitly declaring it as such.
>
> Presumably (I haven't checked), this also applies to u-strings and f-strings
> - is this a documented and known "wart"/edge-case or is it something that
> should be defined and fixed?

Firstly, be aware that there's no such thing as a "raw string" - what
you have is a "raw string literal". It's a purely syntactic feature.
The repr of a string indicates the contents of the string object, and
raw literals and non-raw literals can produce the same resulting
string objects.

The string "\t" gets shown in the repr as "\t". It is a string
consisting of one character, U+0009, a tab. The string r"\t" is shown
as "\\t" and consists of two characters, REVERSE SOLIDUS and LATIN
SMALL LETTER T. That might be why you think there's confusing stuff
happening :)

ChrisA