Interpreting \ escape sequences in strings

[Paul Watson]

How can I get the escapes from a command line parameter interpreted?

The user provides a string on the command line.  The string might contain
traditional escapes such as \t, \n, etc.  It might also contain escaped
octal or hex such as \001 or \x09.

The escapes are coming into sys.argv[] without shell interpretation.  Do I
need to use the compile module to make this work?  Any suggestions?

===
$ cat ./try_arglen2.py
#! /usr/bin/env python
import sys, StringIO
print sys.argv[1]

print sys.argv[1] % ()

sf = StringIO.StringIO()
print >> sf, sys.argv[1],
c = sf.getvalue()
sf.close()
print "now" + c + "is" + c + "the"

# This works because the interpreter is processing the escapes.

sf = StringIO.StringIO("\001")
c = sf.getvalue()
sf.close()
print "now" + c + "is" + c + "the"

===
$ ./try_arglen2.py '\001'
\001
\001
now\001is\001the
now?is?the