unescape escapes in strings

[bvdp]

MRAB wrote:
> bvdp wrote:
>>
>> When reading lines of data from a file in the from (no quotes!)
>>
>>     foo\x20bar
>>
>> and I assign to a variable in a line line like:
>>
>>  f = file('infile', 'r')
>>  for a in f:
>>     print a
>>
>> the string is read in as string with the literal characters 'f', 'o' 
>> ... 'x' , '2' ...
>>
>> as compared to an assignment like:
>>
>>  a="foo\x20bar"
>>
>> which is identical to
>>
>> a="foo bar"
>>
>> Okay, so far ... I think this is what I want since my program is using 
>> space characters as delimiters and I'm trying to use the \x20 notation 
>> to avoid splitting.
>>
>> But, now the problem. When I finally assign the string with the \x20 
>> to a variable the literals are still there. And here I really want 
>> them all nicely converted to the desired values.
>>
>> So, the question is: is there an "unescape()" for strings so that 
>> "foo\x20bar" is converted to "foo bar"????
>>
>  >>> a = r"foo\x20bar"
>  >>> print a
> foo\x20bar
>  >>> a = a.decode("string-escape")
>  >>> print a
> foo bar
> 

Thanks ... I think in my original testing I tried decode() but it didn't 
work. Testing more ...

  the file has 2 lines:
   foo bar
   foo\x20bar

and the program to read is:
f=file('in', 'r')
for a in f:
     a = a.strip()
     a=a.decode()
     print list(a)

I get:

python read.py
[]
[u'f', u'o', u'o', u' ', u'b', u'a', u'r']
[u'f', u'o', u'o', u'\\', u'x', u'2', u'0', u'b', u'a', u'r']

So, the \x20 is still literal.

Any other ideas??? I suppose I could write a re expression ... but 
surely that is not needed???