Python Basics: Reading INI Settings with configparser

An INI file groups settings under section headings such as [app]. Python’s standard-library configparser module reads these settings and converts common value types.

Use Python 3.12 or newer in Bash on Linux. Each example runs independently; the file example uses an automatically cleaned temporary directory.

Read values and convert their types

Save as demo_configparser_1.py:

from configparser import ConfigParser

config = ConfigParser()
config.read_string("""
[app]
name = Notebook
workers = 3
enabled = no
""")
app = config["app"]
print("Name:", app["name"])
print("Workers:", app.getint("workers"))
print("Enabled:", app.getboolean("enabled"))

Run it from the directory where you saved it:

python3 demo_configparser_1.py

Output:

Name: Notebook
Workers: 3
Enabled: False

Values start as strings. Use getint() and getboolean() for conversions: bool("no") would incorrectly give True because the string is nonempty. By default, option names ignore case, while section names are case-sensitive.

Open a required settings file

Save as demo_configparser_2.py:

from configparser import ConfigParser
from pathlib import Path
from tempfile import TemporaryDirectory

with TemporaryDirectory() as directory:
    path = Path(directory) / "settings.ini"
    path.write_text("[display]\nlabel = 80% ready\n", encoding="utf-8")
    config = ConfigParser(interpolation=None)
    with path.open(encoding="utf-8") as source:
        config.read_file(source)
    print(config["display"]["label"])

Run it from the directory where you saved it:

python3 demo_configparser_2.py

Output:

80% ready

Opening the file yourself makes a missing required file raise FileNotFoundError. In contrast, config.read() silently skips files it cannot open. Setting interpolation=None treats percent signs literally; the default parser gives % a special role in value substitution.

Separate missing settings from invalid ones

Save as demo_configparser_3.py:

from configparser import ConfigParser

config = ConfigParser()
config.read_string("[DEFAULT]\nretries = 3\n[worker]\nsize = many\n")
worker = config["worker"]
print("Retries:", worker.getint("retries", fallback=1))
print("Region:", worker.get("region", fallback="local"))
try:
    worker.getint("size", fallback=10)
except ValueError:
    print("Size must be an integer")

Run it from the directory where you saved it:

python3 demo_configparser_3.py

Output:

Retries: 3
Region: local
Size must be an integer

DEFAULT supplies shared values before a fallback is considered. A fallback handles an absent option; it does not repair an invalid value. After conversion, check application rules too, such as requiring a positive size.

References

• Python configparser documentation

Acknowledgements

This post was created with assistance from AI.