ConfigParser: use newline in INI file

[Peter Otten]

Thorsten Kampe wrote:

> * Ned Batchelder (Sat, 1 Oct 2016 17:41:28 -0700 (PDT))

>> If you want to have \n mean a newline in your config file, you can
>> do the conversion after you read the value:
>> 
>>     >>> "a\\nb".decode("string-escape")
>>     'a\nb'
> 
> Interesting approach (although it does not work with Python 3: decode
> is only for byte-strings and the string-escape encoding is not
> defined).

The equivalent for Python 3 is

>>> import codecs
>>> codecs.decode("a\\nb", "unicode-escape")
'a\nb'

You can teach ConfigParser to do this automatically with a custom 
Interpolation:

$ cat cpdemo.py
#!/usr/bin/env python3
import configparser as cp
import codecs

class MyInterpolation(cp.BasicInterpolation):
    def before_get(self, parser, section, option, value, defaults):
        return super().before_get(
            parser, section, option,
            codecs.decode(value, "unicode-escape"),
            defaults)

p = cp.ConfigParser(interpolation=MyInterpolation())
p.read_string("""\
[foo]
bar=ham\\nspam
""")
print(p["foo"]["bar"])    
$ ./cpdemo.py 
ham
spam