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How to read and write INI file with Python3?

Posted by: admin November 30, 2017 Leave a comment

Questions:

I need to read, write and create an INI file with Python3.

FILE.INI

default_path = "/path/name/"
default_file = "file.txt"

Python File:

#    read file and if not exists
ini = iniFile( 'FILE.INI' )

#    Get and Print Config Line "default_path"
getLine = ini.default_path

#    Print (string)/path/name
print getLine

#    Append new line and if exists edit this line
ini.append( 'default_path' , 'var/shared/' )

ini.append( 'default_message' , 'Hey! help me!!' )

UPDATE FILE.INI

default_path    = "var/shared/"
default_file    = "file.txt"
default_message = "Hey! help me!!"
Answers:

This can be something to start with:

import configparser

config = configparser.ConfigParser()
config.read('FILE.INI')
print(config['DEFAULT']['path'])     # -> "/path/name/"
config['DEFAULT']['path'] = '/var/shared/'    # update
config['DEFAULT']['default_message'] = 'Hey! help me!!'   # create

with open('FILE.INI', 'w') as configfile:    # save
    config.write(configfile)

You can find more at the official configparser documentation.

Questions:
Answers:

Here’s a complete read, update and write example.

Input file, test.ini

[section_a]
string_val = hello
bool_val = false
int_val = 11
pi_val = 3.14

Working code.

try:
    from configparser import ConfigParser
except ImportError:
    from ConfigParser import ConfigParser  # ver. < 3.0

# instantiate
config = ConfigParser()

# parse existing file
config.read('test.ini')

# read values from a section
string_val = config.get('section_a', 'string_val')
bool_val = config.getboolean('section_a', 'bool_val')
int_val = config.getint('section_a', 'int_val')
float_val = config.getfloat('section_a', 'pi_val')

# update existing value
config.set('section_a', 'string_val', 'world')

# add a new section and some values
config.add_section('section_b')
config.set('section_b', 'meal_val', 'spam')
config.set('section_b', 'not_found_val', 404)

# save to a file
with open('test_update.ini', 'w') as configfile:
    config.write(configfile)

Output file, test_update.ini

[section_a]
string_val = world
bool_val = false
int_val = 11
pi_val = 3.14

[section_b]
meal_val = spam
not_found_val = 404

The original input file remains untouched.

Questions:
Answers:

http://docs.python.org/library/configparser.html

Python’s standard library might be helpful in this case.

Questions:
Answers:

The standard ConfigParser normally requires access via config['section_name']['key'], which is no fun. A little modification can deliver attribute access:

class AttrDict(dict):
    def __init__(self, *args, **kwargs):
        super(AttrDict, self).__init__(*args, **kwargs)
        self.__dict__ = self

AttrDict is a class derived from dict which allows access via both dictionary keys and attribute access: that means a.x is a['x']

We can use this class in ConfigParser:

config = configparser.ConfigParser(dict_type=AttrDict)
config.read('application.ini')

and now we get application.ini with:

[general]
key = value

as

>>> config._sections.general.key
'value'

Questions:
Answers:

ConfigObj is a good alternative to ConfigParser which offers a lot more flexibility:

  • Nested sections (subsections), to any level
  • List values
  • Multiple line values
  • String interpolation (substitution)
  • Integrated with a powerful validation system including automatic type checking/conversion repeated sections and allowing default values
  • When writing out config files, ConfigObj preserves all comments and the order of members and sections
  • Many useful methods and options for working with configuration files (like the ‘reload’ method)
  • Full Unicode support

It has some draw backs:

  • You cannot set the delimiter, it has to be =… (pull request)
  • You cannot have empty values, well you can but they look liked: fuabr = instead of just fubar which looks weird and wrong.