如何在configobj值中转义％符号？

Question

I'd like to use both parse time and runtime interpolation for values of a configobj configuration file. The easiest way to do simple string interpolation in Python is "%(foo)s" % somedict . Unfortunately configobj uses the same interpolation mechanism and I have not yet found a way to escape it. Ideally my value would look like:

othervar = foo
someconfigobjkey = %(othervar)s %%(runtimevar)s

However configobj tries (and fails) to replace the second variable. Another way to answer this question is to provide a different (configobj) way to do both parse time and runtime interpolation.

Answer 1

Things may have changed since this question was posted, but I've discovered that you can escape using the '%' char. This worked for me in Python 3.

In my config.ini file:

[LOGGING]
format = %%(asctime)-15s %%(message)s

In my python script file:

import configparser

# Load configuration
config = configparser.ConfigParser()
config.read("config.ini")

log_config = config['LOGGING']

print(log_config['format']) # prints out '%(asctime)-15s %(message)s'

Hope it helps someone in the future (:

Answer 2

Yes, unfortunately configobj does not follow normal standard Python formatting rules, so %% , which would otherwise be the correct way to escape a percent sign, fails. Seems like a bit of a design flaw to me.

The only way I can think of to have a literal %(foo)s sequence in a configobj value would be to ensure part of that sequence is itself generated by a replacement:

>>> import configobj
>>> c= configobject.ConfigObj()
>>> c['foo']= 'bar'
>>> c['pc']= '%'
>>> c['v']= '%(foo)s %(pc)s(foo)s'
>>> c['v']
'bar %(foo)s'

Answer 3

Try using '%'+'(foo)s'. That worked for me when dealing with ConfigParser.

Answer 4

Digging deeper in the documentation I found a solution that fits better than the one proposed by bobince: Use a different interpolation engine, such as interpolation="template" . It has two advantages.

1. Does not interfere with % signs.
2. Supports escaping. ( $$ gets interpolated to $ .)

The example would look like:

othervar = foo
someconfigobjkey = $othervar %(runtimevar)s

Answer 5

New version of the answer:

You could use "".format() (Python 2.6 or above) or string.Template (Python 2.4 or above) for the runtime interpolation -- both of which would eliminate the conflict.

(The old version assumed the use of the standard ConfigParser module, hence the comments.)