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Configuration Files in Python

  1. Quick Overview (Basic configuration file).
  2. How to make it.
  3. How to access them.
  4. How to update it.
  5. Real Example.

Quick Overview (Basic Configuration File)

  • The Files consist of sections.
  • Name of the section is withing [] , Example: [DEFAULT] or [testing].
  • Each section will contain keys with values
  • The extension of the file is .ini

Content from python docs

Supported structure

  • Section names are case-sensitive [Default] is different than [default].
  • Spaces are allowed in the keys and the values, my key = my value
  • = or : can be used to separate keys and values.
  • keys with no values can omit = or it can be used if is not followed by any character, my key without value or my key without value = are correct.
  • Comments can be added with # or ; like # I am a comment and ; me too.
  • A section can be indented.

configuration_file_002.png

How to make it

I can make a config file in two ways:

  1. Creating the file and saving it with a .ini extension.
  2. Creating the file programmatically.

Creating a file programmatically can be done using a code similar to this:

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import configparser

config = configparser.ConfigParser()
config['DEFAULT'] = {'API key': 'MYLONGAPIKEY99999',
                      'endpoint': 'http://nosecure.endpoint',
                      'sandbox_endpoint': 'https://secure.endpoint'}

# creating an empty section
config['Debugging'] = {}
config['Debugging']['logger_level'] = 'DEBUG'

config['superSecretData'] = {}
#assigning section to a variable
supersecret = config['superSecretData']
supersecret ['myPassword'] = '123456'
supersecret ['username'] = 'me'

#adding to an existing section
config['DEFAULT']['onLine'] = 'yes'

with open('myExample.ini', 'w') as configfile:
    config.write(configfile)

configuration_file_003.png

All the values stored in the keys are strings, however, there is one method I can use to get a boolean value for keys holding strings like yes, no 'on','off','true','false','1','0'.

How to access them

ConfigParser class provides methods to interact with the configuration file.

read()

Allow me to read the .ini file

sections()

returns the section names present in the config file.

getboolean()

will return a Boolean value depending on the value store in the key, values most be 'yes'/'no', 'on'/'off', 'true'/'false' and '1'/'0'.

Here are some examples of interactions with a config file.

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import configparser

config = configparser.ConfigParser()
config.read('myExample.ini')
print(f'config.sections() => {config.sections()}')
print(f'config["DEFAULT"]["API key"] => {config["DEFAULT"]["API key"] }')
default = config['DEFAULT']
print(f'default["onLine"]  => {default["onLine"] }')

configuration_file_004.png

Like the dictionaries I can provide a Fallback value, that is when the key doesn't I can create it and give it a value.

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>>> default.get('last_name','Fernandez')
Fernandez

How to update it.

To update it I can use the following methods:

add_section() to add a new section.

set(’my_section’,’my_new_key’,’my_new_value’) To add a new key-value pair to an specific session.

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import configparser

config = configparser.ConfigParser()
config.read('myExample.ini')
print(f'current sections: {config.sections()}')

#adding new section and key-value
config.add_section('new_section')
config.set(section='new_section', option='new_key', value='new_value')

with open('myExample.ini', 'w') as configfile:
    config.write(configfile)

Notice I need to “save the changes” by writing the configuration file one more time.