[Python-Dev] eval and triple quoted strings (original) (raw)

Walter Dörwald walter at livinglogic.de
Mon Jun 17 19:04:41 CEST 2013

On 14.06.13 23:03, PJ Eby wrote:

On Fri, Jun 14, 2013 at 2:11 PM, Ron Adam <ron3200 at gmail.com> wrote:

On 06/14/2013 10:36 AM, Guido van Rossum wrote: Not a bug. The same is done for file input -- CRLF is changed to LF before tokenizing.

Should this be the same? python3 -c 'print(bytes("""\r\n""", "utf8"))' b'\r\n'

eval('print(bytes("""\r\n""", "utf8"))') b'\n' No, but: eval(r'print(bytes("""\r\n""", "utf8"))') should be. (And is.) What I believe you and Walter are missing is that the \r\n in the eval strings are converted early if you don't make the enclosing string raw. So what you're eval-ing is not what you think you are eval-ing, hence the confusion.

I expected that eval()ing a string that contains the characters

U+0027: APOSTROPHE
U+0027: APOSTROPHE
U+0027: APOSTROPHE
U+000D: CR
U+000A: LR
U+0027: APOSTROPHE
U+0027: APOSTROPHE
U+0027: APOSTROPHE

to return a string containing the characters:

U+000D: CR
U+000A: LR

Making the string raw, of course turns it into:

U+0027: APOSTROPHE
U+0027: APOSTROPHE
U+0027: APOSTROPHE
U+005C: REVERSE SOLIDUS
U+0072: LATIN SMALL LETTER R
U+005C: REVERSE SOLIDUS
U+006E: LATIN SMALL LETTER N
U+0027: APOSTROPHE
U+0027: APOSTROPHE
U+0027: APOSTROPHE

and eval()ing that does indeed give "\r\n" as expected.

Hmm, it seems that codecs.unicode_escape_decode() does what I want:

codecs.unicode_escape_decode("\r\n\r\n\x0d\x0a\u000d\u000a") ('\r\n\r\n\r\n\r\n', 26)

Servus, Walter

More information about the Python-Dev mailing list