Reading \n unescaped from a file

[Rob Hills]

Hi,

On 03/09/15 06:31, MRAB wrote:
> On 2015-09-02 03:03, Rob Hills wrote:
>> I am developing code (Python 3.4) that transforms text data from one
>> format to another.
>>
>> As part of the process, I had a set of hard-coded str.replace(...)
>> functions that I used to clean up the incoming text into the desired
>> output format, something like this:
>>
>>      dataIn = dataIn.replace('\r', '\\n') # Tidy up linefeeds
>>      dataIn = dataIn.replace('<','<') # Tidy up < character
>>      dataIn = dataIn.replace('>','>') # Tidy up < character
>>      dataIn = dataIn.replace('o','o') # No idea why but lots of
>> these: convert to 'o' character
>>      dataIn = dataIn.replace('f','f') # .. and these: convert to
>> 'f' character
>>      dataIn = dataIn.replace('e','e') # ..  'e'
>>      dataIn = dataIn.replace('O','O') # ..  'O'
>>
> The problem with this approach is that the order of the replacements
> matters. For example, changing '<' to '<' and then '&' to '&'
> can give a different result to changing '&' to '&' and then '<'
> to '<'. If you started with the string '&lt;', then the first order
> would go '&lt;' => '&lt;' => '<', whereas the second order
> would go '&lt;' => '<' => '<'.

Ah yes, thanks for reminding me about that.  I've since modified my code
to use a collections.OrderedDict to store my mappings.

...

>> This all works "as advertised" */except/* for the '\r' => '\\n'
>> replacement. Debugging the code, I see that my '\r' character is
>> "escaped" to '\\r' and the '\\n' to '\\\\n' when they are read in from
>> the file.
>>
>> I've been googling hard and reading the Python docs, trying to get my
>> head around character encoding, but I just can't figure out how to get
>> these bits of code to do what I want.
>>
>> It seems to me that I need to either:
>>
>>   * change the way I represent '\r' and '\\n' in my mapping file; or
>>   * transform them somehow when I read them in
>>
>> However, I haven't figured out how to do either of these.
>>
> Try ast.literal_eval, although you'd need to make it look like a string
> literal first:

Thanks for the suggestion.  For now, I've decided I was being too
pedantic trying to load my two escaped strings from a file and I've
simply hard coded them and moved on to other issues.  I'll try this idea
later on though.

Cheers,

-- 
Rob Hills
Waikiki, Western Australia