>>> parser = ConfigParser.SafeConfigParser()
>>> parser.add_section("test")
>>> parser.set("test", "foo", "bar%bar")
>>> parser.write(open("test.config", "w"))
>>> parser2 = ConfigParser.SafeConfigParser()
>>> parser2.readfp(open("test.config"))
>>> parser.get("test", "foo")
Traceback (most recent call last):
  File "<stdin>", line 1, in ?
  File "/usr/lib/python2.4/ConfigParser.py", line 525, in get
    return self._interpolate(section, option, value, d)
  File "/usr/lib/python2.4/ConfigParser.py", line 593, in _interpolate
    self._interpolate_some(option, L, rawval, section, vars, 1)
  File "/usr/lib/python2.4/ConfigParser.py", line 634, in _interpolate_some
    "'%%' must be followed by '%%' or '(', found: %r" % (rest,))
ConfigParser.InterpolationSyntaxError: '%' must be followed by '%' or '(', found: '%bar'


Problem: SaveConfigParser saves the string "bar%bar" as is and not as "bar%%bar".

I'm not sure that automagically changing their input is such a great idea.  I'm -0 for automagically changing their input, but +1 for raising ValueError when the input contains a string that can't be properly interpolated.  I've implemented the patch both ways.  Anyone else have an opinion about this?

Examples of such malformatted strings include bar%bar and bar%.

Initially, I believed ValueError was the appropriate way to go with this. However, when I thought about how I use ConfigParser, I realized that it would be far nicer if it simply worked.

See the patches in 1635639.
http://sourceforge.net/tracker/index.php?func=detail&aid=1635639&group_id=5470&atid=105470

Good catch on this.  I haven't caught it and I've been using ConfigParser for a while now.

Closing this as a duplicate.