Reading backslashed characters (in ASCII) from a file

[Dinu C. Gherman]

I'm reading data from a file that contains octal coded characters
(and other baskslashed ones) in ASCII like this:

\163\160\141\155 and \145\147\147\163

Using the normal read(<n>) method on file objects I assemble parts of
the data (containing these octal chars) into Python strings.

The problem I face now is that I want to convert these characters
into their ASCII representation in a Python string. I know that
Python does that itself, but the string is composed peu a peu and
the upper example should look like this when splitted:

['s','p','a','m', ...]

instead of:

['\\','1','6','3','\\', ...]

I already thought of using the re module, but so far I'm led to
believe that this is going to be a backslashing-nightmare. Another
idea was to use exec() or eval() to get Python interpret the
backslashes in the usual way, but that doesn't work either. In
fact, the same problem holds for getting \n, \t characters, etc.

Also trying to read a whole chunk of the file to avoid dealing
with incrementally growing strings does not help as the following
example shows (BTW, reading with "r" or "rb" makes no difference):

1. Write "\163\160\141\155 and \145\147\147\163
   to an ASCII file named "backslash" using one's favorite
   editor like emacs.

2. Call Python and do the following:

>>> f = open("backslash", "rb")
>>> f.read()
'(\\163\\160\\141\\155 and \\145\\147\\147\\163)'
>>>

Now I'm quite puzzled. Is there really no way but using the re module
excessively? Anybody having a better trick?

Dinu

---
Dinu C. Gherman
LHS International AG


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