[Python-Dev] eval and triple quoted strings

[Guido van Rossum]

The semantics of raw strings are clear. I don't see that they should be
called out especially in any context. (Except for regexps.) Usually exec()
is not used with a literal anyway (what would be the point).

--Guido van Rossum (sent from Android phone)
On Jun 15, 2013 1:03 PM, "Ron Adam" <ron3200 at gmail.com> wrote:

>
>
> On 06/14/2013 04:03 PM, PJ Eby wrote:
>
>> >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.
>>
>
> Yes thanks, seems like an easy mistake to make.
>
> To be clear...
>
> The string to eval is parsed when the eval line is tokenized in the scope
> containing the eval() function.  The eval function then parses the
> resulting string object it receives as it's input.
>
> There is no mention of using raw strings in the docs on evel and exec.  I
> think there should be, because the intention (in most cases) is for eval to
> parse the string, and not for it to be parsed or changed before it's
> evaluated by eval or exec.
>
> An example using a string with escape characters might make it clearer.
>
> Cheers,
>    Ron
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