flask.app ImmutableDict Example Code

ImmutableDict is a class within the flask.app module of the Flask framework that is actually imported from the Werkzeug datastructures module. The ImmutableDict class wraps a standard Python dictionary so that values cannot be modified after initially being set.

BadRequest, Flask, and Headers are several other callables with code examples from the same flask.app package.

These topics are also useful while reading the ImmutableDict examples:

Example 1 from indico

indico (project website, documentation and sandbox demo) is a Flask-based web app for event management. The code is open sourced under the MIT license.

indico / indico / core / config.py

# config.py

import ast
import codecs
import os
import re
import socket
import warnings
from datetime import timedelta

import pytz
from celery.schedules import crontab
from flask import current_app, g
from flask.helpers import get_root_path
from werkzeug.datastructures import ImmutableDict
from werkzeug.urls import url_parse

from indico.util.caching import make_hashable
from indico.util.fs import resolve_link
from indico.util.packaging import package_is_editable
from indico.util.string import crc32, snakify

    'ATTACHMENT_STORAGE': 'default',
    'BASE_URL': None,
    'CACHE_DIR': '/opt/indico/cache',
    'CELERY_BROKER': None,
    'CELERY_CONFIG': {},
    'COMMUNITY_HUB_URL': 'https://hub.getindico.io',
    'DB_LOG': False,
    'DEBUG': False,

## ... source file abbreviated to get to ImmutableDict examples ...

        allowed |= set(INTERNAL_DEFAULTS)
    for key in set(data) - allowed:
        warnings.warn(f'Ignoring unknown config key {key}')
    return {k: v for k, v in data.items() if k in allowed}

def load_config(only_defaults=False, override=None):
    if not only_defaults:
        path = get_config_path()
        config = _sanitize_data(_parse_config(path))
        env_override = os.environ.get('INDICO_CONF_OVERRIDE')
        if env_override:
        resolved_path = resolve_link(path) if os.path.islink(path) else path
        resolved_path = None if resolved_path == os.devnull else resolved_path
        data['CONFIG_PATH'] = path
        data['CONFIG_PATH_RESOLVED'] = resolved_path
        if resolved_path is not None:
            data['LOGGING_CONFIG_PATH'] = os.path.join(os.path.dirname(resolved_path), data['LOGGING_CONFIG_FILE'])

    if override:
        data.update(_sanitize_data(override, allow_internal=True))
    return ImmutableDict(data)

class IndicoConfig:

    __slots__ = ('_config', '_exc')

    def __init__(self, config=None, exc=AttributeError):
        object.__setattr__(self, '_config', config)
        object.__setattr__(self, '_exc', exc)

    def data(self):
            return self._config or current_app.config['INDICO']
        except KeyError:
            raise RuntimeError('config not loaded')

    def hash(self):
        return crc32(repr(make_hashable(sorted(self.data.items()))))

        return self.BASE_URL + '/css/confTemplates'

## ... source file continues with no further ImmutableDict examples...

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