Lists in ConfigParser

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The typical ConfigParser generated file looks like:

[Section]
bar=foo
[Section 2]
bar2= baz

Now, is there a way to index lists like, for instance:

[Section 3]
barList={
    item1,
    item2
}

Related question: Python’s ConfigParser unique keys per section

18 Answers

I am using a combination of ConfigParser and JSON:

[Foo]
fibs: [1,1,2,3,5,8,13]

just read it with:

>>> json.loads(config.get("Foo","fibs"))
[1, 1, 2, 3, 5, 8, 13]

You can even break lines if your list is long (thanks @peter-smit):

[Bar]
files_to_check = [
     "/path/to/file1",
     "/path/to/file2",
     "/path/to/another file with space in the name"
     ]

Of course i could just use JSON, but i find config files much more readable, and the [DEFAULT] Section very handy.

There is nothing stopping you from packing the list into a delimited string and then unpacking it once you get the string from the config. If you did it this way your config section would look like:

[Section 3]
barList=item1,item2

It's not pretty but it's functional for most simple lists.

No mention of the converters kwarg for ConfigParser() in any of these answers was rather disappointing.

According to the documentation you can pass a dictionary to ConfigParser that will add a get method for both the parser and section proxies. So for a list:

example.ini

[Germ]
germs: a,list,of,names, and,1,2, 3,numbers

Parser example:

cp = ConfigParser(converters={'list': lambda x: [i.strip() for i in x.split(',')]})
cp.read('example.ini')
cp.getlist('Germ', 'germs')
['a', 'list', 'of', 'names', 'and', '1', '2', '3', 'numbers']
cp['Germ'].getlist('germs')
['a', 'list', 'of', 'names', 'and', '1', '2', '3', 'numbers']

This is my personal favorite as no subclassing is necessary and I don't have to rely on an end user to perfectly write JSON or a list that can be interpreted by ast.literal_eval.

I completed similar task in my project with section with keys without values:

import configparser

# allow_no_value param says that no value keys are ok
config = configparser.ConfigParser(allow_no_value=True)

# overwrite optionxform method for overriding default behaviour (I didn't want lowercased keys)
config.optionxform = lambda optionstr: optionstr

config.read('./app.config')

features = list(config['FEATURES'].keys())

print(features)

Output:

['BIOtag', 'TextPosition', 'IsNoun', 'IsNomn']

app.config:

[FEATURES]
BIOtag
TextPosition
IsNoun
IsNomn

So another way, which I prefer, is to just split the values, for example:

#/path/to/config.cfg
[Numbers]
first_row = 1,2,4,8,12,24,36,48

Could be loaded like this into a list of strings or integers, as follows:

import configparser

config = configparser.ConfigParser()
config.read('/path/to/config.cfg')

# Load into a list of strings
first_row_strings = config.get('Numbers', 'first_row').split(',')

# Load into a list of integers
first_row_integers = [int(x) for x in config.get('Numbers', 'first_row').split(',')]

This method prevents you from needing to wrap your values in brackets to load as JSON.

Only primitive types are supported for serialization by config parser. I would use JSON or YAML for that kind of requirement.

To take Grr's answer (my favorite) a step further, instead of enclosing list items in quotes in the .ini file, you can use the map function. This allows you to pythonically specify list item datatypes.

Config file:

[section]
listKey1: 1001, 1002, 1003
listKey2: AAAA, BBBB, CCCC

Code:

cfgFile = 'config.ini'
parser = ConfigParser(converters={'list': lambda x: [i.strip() for i in x.split(',')]})
parser.read(cfgFile)

list1 = list(map(int, parser.getlist('section', 'listKey1')))
list2 = list(map(str, parser.getlist('section', 'listKey2')))

print(list1)
print(list2)

Output:

[1001, 1002, 1003]
['AAAA', 'BBBB', 'CCCC']

If this is your config.ini:

[Section 3]
barList=item1,item2

Then with configparser you could do this:

from configparser import ConfigParser
config = ConfigParser()
config.read('config.ini')
my_list = config['Section 3']['barList'].split(',')

You will get:

 my_list =  ['item1', 'item2']

The split()-method will return a list, see Python string docs.

If you have white spaces in your config.ini like this:

[Section 3]
barList= item1, item2

Then you'd better do this:

my_list = [x.strip() for x in config['Section 3']['barList'].split(',')]

If your items are numbers (integers for instance), just apply:

my_list_of_ints = list(map(int, my_list))

You will get:

my_list_of_ints =  [item1, item2]

I faced the same problem in the past. If you need more complex lists, consider creating your own parser by inheriting from ConfigParser. Then you would overwrite the get method with that:

    def get(self, section, option):
    """ Get a parameter
    if the returning value is a list, convert string value to a python list"""
    value = SafeConfigParser.get(self, section, option)
    if (value[0] == "[") and (value[-1] == "]"):
        return eval(value)
    else:
        return value

With this solution you will also be able to define dictionaries in your config file.

But be careful! This is not as safe: this means anyone could run code through your config file. If security is not an issue in your project, I would consider using directly python classes as config files. The following is much more powerful and expendable than a ConfigParser file:

class Section
    bar = foo
class Section2
    bar2 = baz
class Section3
    barList=[ item1, item2 ]

json.loads & ast.literal_eval seems to be working but simple list within config is treating each character as byte so returning even square bracket....

meaning if config has fieldvalue = [1,2,3,4,5]

then config.read(*.cfg) config['fieldValue'][0] returning [ in place of 1

As mentioned by Peter Smit (https://stackoverflow.com/a/11866695/7424596) You might want to extend ConfigParser, in addition, an Interpolator can be used to automatically convert into and from the list.

For reference at the bottom you can find code which automatically converts config like:

[DEFAULT]
keys = [
    Overall cost structure, Capacity, RAW MATERIALS,
    BY-PRODUCT CREDITS, UTILITIES, PLANT GATE COST,
    PROCESS DESCRIPTION, AT 50% CAPACITY, PRODUCTION COSTS,
    INVESTMENT, US$ MILLION, PRODUCTION COSTS, US ¢/LB,
    VARIABLE COSTS, PRODUCTION COSTS, MAINTENANCE MATERIALS
  ]

So if you request keys you will get:

<class 'list'>: ['Overall cost structure', 'Capacity', 'RAW MATERIALS', 'BY-PRODUCT CREDITS', 'UTILITIES', 'PLANT GATE COST', 'PROCESS DESCRIPTION', 'AT 50% CAPACITY', 'PRODUCTION COSTS', 'INVESTMENT', 'US$ MILLION', 'PRODUCTION COSTS', 'US ¢/LB', 'VARIABLE COSTS', 'PRODUCTION COSTS', 'MAINTENANCE MATERIALS']

Code:

class AdvancedInterpolator(Interpolation):
    def before_get(self, parser, section, option, value, defaults):
        is_list = re.search(parser.LIST_MATCHER, value)
        if is_list:
            return parser.getlist(section, option, raw=True)
        return value


class AdvancedConfigParser(ConfigParser):

    _DEFAULT_INTERPOLATION = AdvancedInterpolator()

    LIST_SPLITTER = '\s*,\s*'
    LIST_MATCHER = '^\[([\s\S]*)\]$'

    def _to_list(self, str):
        is_list = re.search(self.LIST_MATCHER, str)
        if is_list:
            return re.split(self.LIST_SPLITTER, is_list.group(1))
        else:
            return re.split(self.LIST_SPLITTER, str)


    def getlist(self, section, option, conv=lambda x:x.strip(), *, raw=False, vars=None,
                  fallback=_UNSET, **kwargs):
        return self._get_conv(
                section, option,
                lambda value: [conv(x) for x in self._to_list(value)],
                raw=raw,
                vars=vars,
                fallback=fallback,
                **kwargs
        )

    def getlistint(self, section, option, *, raw=False, vars=None,
            fallback=_UNSET, **kwargs):
        return self.getlist(section, option, int, raw=raw, vars=vars,
                fallback=fallback, **kwargs)

    def getlistfloat(self, section, option, *, raw=False, vars=None,
            fallback=_UNSET, **kwargs):
        return self.getlist(section, option, float, raw=raw, vars=vars,
                fallback=fallback, **kwargs)

    def getlistboolean(self, section, option, *, raw=False, vars=None,
            fallback=_UNSET, **kwargs):
        return self.getlist(section, option, self._convert_to_boolean,
                raw=raw, vars=vars, fallback=fallback, **kwargs)

Ps keep in mind importance of indentdation. As reads in ConfigParser doc string:

Values can span multiple lines, as long as they are indented deeper than the first line of the value. Depending on the parser's mode, blank lines may be treated as parts of multiline values or ignored.

you can use list in config file then parse it in python

from ast import literal_eval

literal_eval("[1,2,3,4]")

import json

json.loads("[1,2,3,4]")

and also you can use json file behind your config file like this:

your config file :
[A]
json_dis = .example.jason
--------------------
your code :
import configparser
config = configparser.ConfigParser()
config.read('config.ini')
# getting items of section A
config.items('A')
# result is a list of key-values
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