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Version: Config V2

Python SDK Reference

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ConfigCat Python SDK on GitHub

Getting started

1. Install ConfigCat SDK

pip install configcat-client

2. Import the package

import configcatclient

3. Create the ConfigCat client with your SDK Key

client = configcatclient.get('#YOUR-SDK-KEY#')

4. Get your setting value

is_my_awesome_feature_enabled = client.get_value('isMyAwesomeFeatureEnabled', False)
if is_my_awesome_feature_enabled:
do_the_new_thing()
else:
do_the_old_thing()

5. Stop ConfigCat client

You can safely shut down all clients at once or individually and release all associated resources on application exit.

configcatclient.close_all() # closes all clients

client.close() # closes a specific client

Creating the ConfigCat Client

ConfigCat Client is responsible for:

  • managing the communication between your application and ConfigCat servers.
  • caching your setting values and feature flags.
  • serving values quickly in a failsafe way.

configcatclient.get('#YOUR-SDK-KEY#') returns a client with default options.

Client optionsDescriptionDefault
base_urlObsolete, sets the CDN base url (forward proxy, dedicated subscription) from where the sdk will download the config JSON.None
polling_modeSets the polling mode for the client. More about polling modes.PollingMode.auto_poll()
config_cacheSets a custom config cache implementation for the client. More about cache.None
proxiesSets custom proxies for the client. More about proxy.None
proxy_authSets proxy authentication for the custom proxies. More about proxy.None
connect_timeout_secondsThe number of seconds to wait for the server to make the initial connection (i.e. completing the TCP connection handshake).10
read_timeout_secondsThe number of seconds to wait for the server to respond before giving up.30
flag_overridesLocal feature flag & setting overrides. More about feature flag overridesNone
data_governanceDescribes the location of your feature flag and setting data within the ConfigCat CDN. This parameter needs to be in sync with your Data Governance preferences. More about Data Governance. Available options: Global, EuOnly.Global
default_userSets the default user. More about default user.None
hooksUsed to subscribe events that the SDK sends in specific scenarios. More about hooks.None
offlineIndicates whether the SDK should be initialized in offline mode. More about offline mode.False
client = configcatclient.get('#YOUR-SDK-KEY#',
ConfigCatOptions(
polling_mode=PollingMode.auto_poll()
)
)
caution

We strongly recommend you to use the ConfigCat Client as a Singleton object in your application. The configcatclient.get() static factory method constructs singleton client instances for your SDK keys. These clients can be closed all at once with the configcatclient.close_all() method or individually with client.close().

Anatomy of get_value()

ParametersDescription
keyREQUIRED. Setting-specific key. Set on ConfigCat Dashboard for each setting.
default_valueREQUIRED. This value will be returned in case of an error.
userOptional, User Object. Essential when using Targeting. Read more about Targeting.
value = client.get_value(
'keyOfMySetting', # Setting Key
False, # Default value
User('#UNIQUE-USER-IDENTIFIER#') # Optional User Object
)

Anatomy of get_value_details()

get_value_details() is similar to get_value() but instead of returning the evaluated value only, it gives an EvaluationDetails object with more detailed information about the evaluation result.

ParametersDescription
keyREQUIRED. Setting-specific key. Set on ConfigCat Dashboard for each setting.
defaultValueREQUIRED. This value will be returned in case of an error.
userOptional, User Object. Essential when using Targeting. Read more about Targeting.
details = client.get_value_details(
'keyOfMySetting', # Setting Key
False, # Default value
User('#UNIQUE-USER-IDENTIFIER#') # Optional User Object
)

The details result contains the following information:

PropertyDescription
valueThe evaluated value of the feature flag or setting.
keyThe key of the evaluated feature flag or setting.
is_default_valueTrue when the default value passed to get_value_details() is returned due to an error.
errorIn case of an error, this property contains the error message.
userThe User Object that was used for evaluation.
matched_targeting_ruleThe Targeting Rule (if any) that matched during the evaluation and was used to return the evaluated value.
matched_percentage_optionThe Percentage Option (if any) that was used to select the evaluated value.
fetch_timeThe last download time (UTC datetime) of the current config.

User Object

The User Object is essential if you'd like to use ConfigCat's Targeting feature.

user_object = User('#UNIQUE-USER-IDENTIFIER#')
user_object = User('[email protected]')

Customized User Object creation

ParametersDescription
identifierREQUIRED. Unique identifier of a user in your application. Can be any string value, even an email address.
emailOptional parameter for easier Targeting Rule definitions.
countryOptional parameter for easier Targeting Rule definitions.
customOptional dictionary for custom attributes of a user for advanced Targeting Rule definitions. E.g. User role, Subscription type.
user_object = User(
'#UNIQUE-USER-IDENTIFIER#',
'john@example',
'United Kingdom',
{ SubscriptionType: 'Pro', UserRole: 'Admin' }
)

The custom dictionary also allows attribute values other than string values:

user_object = User(
'#UNIQUE-USER-IDENTIFIER#',
custom={
'Rating': 4.5,
'RegisteredAt': datetime.fromisoformat('2023-11-22 12:34:56 +00:00'),
'Roles': [ 'Role1', 'Role2' ]
}
)

User Object Attribute Types

All comparators support string values as User Object attribute (in some cases they need to be provided in a specific format though, see below), but some of them also support other types of values. It depends on the comparator how the values will be handled. The following rules apply:

Text-based comparators (EQUALS, IS_ONE_OF, etc.)

  • accept string values,
  • all other values are automatically converted to string (a warning will be logged but evaluation will continue as normal).

SemVer-based comparators (IS_ONE_OF_SEMVER, LESS_THAN_SEMVER, GREATER_THAN_SEMVER, etc.)

  • accept string values containing a properly formatted, valid semver value,
  • all other values are considered invalid (a warning will be logged and the currently evaluated Targeting Rule will be skipped).

Number-based comparators (EQUALS_NUMBER, LESS_THAN_NUMBER, GREATER_THAN_OR_EQUAL_NUMBER, etc.)

  • accept float values and all other numeric values which can safely be converted to float,
  • accept string values containing a properly formatted, valid float value,
  • all other values are considered invalid (a warning will be logged and the currently evaluated Targeting Rule will be skipped).

Date time-based comparators (BEFORE_DATETIME / AFTER_DATETIME)

  • accept datetime values, which are automatically converted to a second-based Unix timestamp (datetime values with naive timezone are considered to be in UTC),
  • accept float values representing a second-based Unix timestamp and all other numeric values which can safely be converted to float,
  • accept string values containing a properly formatted, valid float value,
  • all other values are considered invalid (a warning will be logged and the currently evaluated Targeting Rule will be skipped).

String array-based comparators (ARRAY_CONTAINS_ANY_OF / ARRAY_NOT_CONTAINS_ANY_OF)

  • accept arrays of string,
  • accept string values containing a valid JSON string which can be deserialized to an array of string,
  • all other values are considered invalid (a warning will be logged and the currently evaluated Targeting Rule will be skipped).

Default user

There's an option to set a default User Object that will be used at feature flag and setting evaluation. It can be useful when your application has a single user only, or rarely switches users.

You can set the default User Object either on SDK initialization:

client = configcatclient.get('#YOUR-SDK-KEY#',
ConfigCatOptions(
default_user=User('[email protected]')
)
)

or with the set_default_user() method of the ConfigCat client.

client.set_default_user(User('[email protected]'))

Whenever the get_value(), get_value_details(), get_variation_id(), get_all_variation_ids(), or get_all_values() methods are called without an explicit user parameter, the SDK will automatically use the default user as a User Object.

client = configcatclient.get('#YOUR-SDK-KEY#',
ConfigCatOptions(
default_user=User('[email protected]')
)
)
# The default user will be used at the evaluation process.
value = client.get_value('keyOfMySetting', False)

When the user parameter is specified on the requesting method, it takes precedence over the default user.

client = configcatclient.get('#YOUR-SDK-KEY#',
ConfigCatOptions(
default_user=User('[email protected]')
)
)
other_user = User('[email protected]')
# otherUser will be used at the evaluation process.
value = client.get_value('keyOfMySetting', False, other_user)

For deleting the default user, you can do the following:

client.clear_default_user()

Polling Modes

The ConfigCat SDK supports 3 different polling mechanisms to acquire the setting values from ConfigCat. After latest setting values are downloaded, they are stored in the internal cache, then all get_value() calls are served from there. With the following polling modes, you can customize the SDK to best fit to your application's lifecycle.
More about polling modes.

Auto polling (default)

The ConfigCat SDK downloads the latest values and stores them automatically every 60 seconds.

Use the poll_interval_seconds option parameter of the PollingMode.auto_poll() to change the polling interval.

client = configcatclient.get('#YOUR-SDK-KEY#',
ConfigCatOptions(
polling_mode=PollingMode.auto_poll(poll_interval_seconds=95)
)
)

Available options:

Option ParameterDescriptionDefault
poll_interval_secondsPolling interval.60
max_init_wait_time_secondsMaximum waiting time between the client initialization and the first config acquisition in seconds.5
caution

Auto polling mode utilizes its polling job in a threading.Thread object. If you are running your application behind an uWSGI web server, the auto polling mode may not work as expected because the uWSGI web server disables Python's threading by default. Please enable threading or switch to another polling mode in this case.

Lazy loading

When calling get_value(), the ConfigCat SDK downloads the latest setting values if they are not present or expired in the cache. In this case get_value() will return the setting value after the cache is updated.

Use cache_refresh_interval_seconds option parameter to set cache lifetime.

client = configcatclient.get('#YOUR-SDK-KEY#',
ConfigCatOptions(
polling_mode=PollingMode.lazy_load(cache_refresh_interval_seconds=600)
)
)

Available options:

Option ParameterDescriptionDefault
cache_refresh_interval_secondsCache TTL.60

Manual polling

Manual polling gives you full control over when the config JSON (with the setting values) is downloaded. ConfigCat SDK will not update them automatically. Calling force_refresh() is your application's responsibility.

client = configcatclient.get('#YOUR-SDK-KEY#',
ConfigCatOptions(
polling_mode=PollingMode.manual_poll()
)
)
client.force_refresh()

get_value() returns default_value if the cache is empty. Call force_refresh() to update the cache.

client = configcatclient.get('#YOUR-SDK-KEY#',
ConfigCatOptions(
polling_mode=PollingMode.manual_poll()
)
)
value = client.get_value('key', 'my default value') # Returns "my default value"
client.force_refresh()
value = client.get_value('key', 'my default value') # Returns "value from server"

Hooks

With the following hooks you can subscribe to particular events fired by the SDK:

  • on_client_ready(): This event is sent when the SDK reaches the ready state. If the SDK is set up with lazy load or manual polling it's considered ready right after instantiation. If it's using auto polling, the ready state is reached when the SDK has a valid config JSON loaded into memory either from cache or from HTTP. If the config couldn't be loaded neither from cache nor from HTTP the on_client_ready event fires when the auto polling's max_init_wait_time_seconds is reached.

  • on_config_changed(config: dict): This event is sent when the SDK loads a valid config JSON into memory from cache, and each subsequent time when the loaded config JSON changes via HTTP.

  • on_flag_evaluated(evaluation_details: EvaluationDetails): This event is sent each time when the SDK evaluates a feature flag or setting. The event sends the same evaluation details that you would get from get_value_details().

  • on_error(error: str): This event is sent when an error occurs within the ConfigCat SDK.

You can subscribe to these events either on SDK initialization:

def on_flag_evaluated(evaluation_details):
# handle the event
pass

client = configcatclient.get('#YOUR-SDK-KEY#',
ConfigCatOptions(
hooks=Hooks(on_flag_evaluated=on_flag_evaluated)
)
)

or with the get_hooks() method of the ConfigCat client:

client.get_hooks().add_on_flag_evaluated(on_flag_evaluated)

Online / Offline mode

In cases when you'd want to prevent the SDK from making HTTP calls, you can put it in offline mode:

client.set_offline()

In offline mode, the SDK won't initiate HTTP requests and will work only from its cache.

To put the SDK back in online mode, you can do the following:

client.set_online()

With client.is_offline() you can check whether the SDK is in offline mode.

Flag Overrides

With flag overrides you can overwrite the feature flags & settings downloaded from the ConfigCat CDN with local values. Moreover, you can specify how the overrides should apply over the downloaded values. The following 3 behaviours are supported:

  • Local only (OverrideBehaviour.LocalOnly): When evaluating values, the SDK will not use feature flags & settings from the ConfigCat CDN, but it will use all feature flags & settings that are loaded from local-override sources.

  • Local over remote (OverrideBehaviour.LocalOverRemote): When evaluating values, the SDK will use all feature flags & settings that are downloaded from the ConfigCat CDN, plus all feature flags & settings that are loaded from local-override sources. If a feature flag or a setting is defined both in the downloaded and the local-override source then the local-override version will take precedence.

  • Remote over local (OverrideBehaviour.RemoteOverLocal): When evaluating values, the SDK will use all feature flags & settings that are downloaded from the ConfigCat CDN, plus all feature flags & settings that are loaded from local-override sources. If a feature flag or a setting is defined both in the downloaded and the local-override source then the downloaded version will take precedence.

You can set up the SDK to load your feature flag & setting overrides from a file or a dictionary.

JSON File

The SDK can load your feature flag & setting overrides from a file.

File

client = configcatclient.get('#YOUR-SDK-KEY#',
ConfigCatOptions(
flag_overrides=LocalFileFlagOverrides(
file_path='path/to/the/local_flags.json', # path to the file
override_behaviour=OverrideBehaviour.LocalOnly
)
)
)

JSON File Structure

The SDK supports 2 types of JSON structures to describe feature flags & settings.

1. Simple (key-value) structure
{
"flags": {
"enabledFeature": true,
"disabledFeature": false,
"intSetting": 5,
"doubleSetting": 3.14,
"stringSetting": "test"
}
}

This is the same format that the SDK downloads from the ConfigCat CDN. It allows the usage of all features that are available on the ConfigCat Dashboard.

You can download your current config JSON from ConfigCat's CDN and use it as a baseline.

A convenient way to get the config JSON for a specific SDK Key is to install the ConfigCat CLI tool and execute the following command:

configcat config-json get -f v6 -p {YOUR-SDK-KEY} > config.json

(Depending on your Data Governance settings, you may need to add the --eu switch.)

Alternatively, you can download the config JSON manually, based on your Data Governance settings:

  • GLOBAL: https://cdn-global.configcat.com/configuration-files/{YOUR-SDK-KEY}/config_v6.json
  • EU: https://cdn-eu.configcat.com/configuration-files/{YOUR-SDK-KEY}/config_v6.json
{
"p": {
// hash salt, required only when confidential text comparator(s) are used
"s": "80xCU/SlDz1lCiWFaxIBjyJeJecWjq46T4eu6GtozkM="
},
"s": [ // array of segments
{
"n": "Beta Users", // segment name
"r": [ // array of User Conditions (there is a logical AND relation between the elements)
{
"a": "Email", // comparison attribute
"c": 0, // comparator (see below)
"l": [ // comparison value (see below)
"[email protected]", "[email protected]"
]
}
]
}
],
"f": { // key-value map of feature flags & settings
"isFeatureEnabled": { // key of a particular flag / setting
"t": 0, // setting type, possible values:
// 0 -> on/off setting (feature flag)
// 1 -> text setting
// 2 -> whole number setting
// 3 -> decimal number setting
"r": [ // array of Targeting Rules (there is a logical OR relation between the elements)
{
"c": [ // array of conditions (there is a logical AND relation between the elements)
{
"u": { // User Condition
"a": "Email", // comparison attribute
"c": 2, // comparator, possible values and required comparison value types:
// 0 -> IS ONE OF (cleartext) + string array comparison value ("l")
// 1 -> IS NOT ONE OF (cleartext) + string array comparison value ("l")
// 2 -> CONTAINS ANY OF (cleartext) + string array comparison value ("l")
// 3 -> NOT CONTAINS ANY OF (cleartext) + string array comparison value ("l")
// 4 -> IS ONE OF (semver) + semver string array comparison value ("l")
// 5 -> IS NOT ONE OF (semver) + semver string array comparison value ("l")
// 6 -> < (semver) + semver string comparison value ("s")
// 7 -> <= (semver + semver string comparison value ("s")
// 8 -> > (semver) + semver string comparison value ("s")
// 9 -> >= (semver + semver string comparison value ("s")
// 10 -> = (number) + number comparison value ("d")
// 11 -> <> (number + number comparison value ("d")
// 12 -> < (number) + number comparison value ("d")
// 13 -> <= (number + number comparison value ("d")
// 14 -> > (number) + number comparison value ("d")
// 15 -> >= (number) + number comparison value ("d")
// 16 -> IS ONE OF (hashed) + string array comparison value ("l")
// 17 -> IS NOT ONE OF (hashed) + string array comparison value ("l")
// 18 -> BEFORE (UTC datetime) + second-based Unix timestamp number comparison value ("d")
// 19 -> AFTER (UTC datetime) + second-based Unix timestamp number comparison value ("d")
// 20 -> EQUALS (hashed) + string comparison value ("s")
// 21 -> NOT EQUALS (hashed) + string comparison value ("s")
// 22 -> STARTS WITH ANY OF (hashed) + string array comparison value ("l")
// 23 -> NOT STARTS WITH ANY OF (hashed) + string array comparison value ("l")
// 24 -> ENDS WITH ANY OF (hashed) + string array comparison value ("l")
// 25 -> NOT ENDS WITH ANY OF (hashed) + string array comparison value ("l")
// 26 -> ARRAY CONTAINS ANY OF (hashed) + string array comparison value ("l")
// 27 -> ARRAY NOT CONTAINS ANY OF (hashed) + string array comparison value ("l")
// 28 -> EQUALS (cleartext) + string comparison value ("s")
// 29 -> NOT EQUALS (cleartext) + string comparison value ("s")
// 30 -> STARTS WITH ANY OF (cleartext) + string array comparison value ("l")
// 31 -> NOT STARTS WITH ANY OF (cleartext) + string array comparison value ("l")
// 32 -> ENDS WITH ANY OF (cleartext) + string array comparison value ("l")
// 33 -> NOT ENDS WITH ANY OF (cleartext + string array comparison value ("l")
// 34 -> ARRAY CONTAINS ANY OF (cleartext) + string array comparison value ("l")
// 35 -> ARRAY NOT CONTAINS ANY OF (cleartext) + string array comparison value ("l")
"l": [ // comparison value - depending on the comparator, another type of value may need
// to be specified (see above):
// "s": string
// "d": number
"@example.com"
]
}
},
{
"p": { // Flag Condition (Prerequisite)
"f": "mainIntFlag", // key of prerequisite flag
"c": 0, // comparator, possible values: 0 -> EQUALS, 1 -> NOT EQUALS
"v": { // comparison value (value's type must match the prerequisite flag's type)
"i": 42
}
}
},
{
"s": { // Segment Condition
"s": 0, // segment index, a valid index into the top-level segment array ("s")
"c": 1 // comparator, possible values: 0 -> IS IN SEGMENT, 1 -> IS NOT IN SEGMENT
}
}
],
"s": { // alternatively, an array of Percentage Options ("p", see below) can also be specified
"v": { // the value served when the rule is selected during evaluation
"b": true
},
"i": "bcfb84a7"
}
}
],
"p": [ // array of Percentage Options
{
"p": 10, // % value
"v": { // the value served when the Percentage Option is selected during evaluation
"b": true
},
"i": "bcfb84a7"
},
{
"p": 90,
"v": {
"b": false
},
"i": "bddac6ae"
}
],
"v": { // fallback value, served when none of the Targeting Rules match,
// no Percentage Options are defined or evaluation of these is not possible
"b": false // depending on the setting type, another type of value may need to be specified:
// text setting -> "s": string
// whole number setting -> "i": number
// decimal number setting -> "d": number
},
"i": "430bded3" // variation id (for analytical purposes)
}
}
}

For a more comprehensive specification of the config JSON v6 format, you may refer to this JSON schema document.

Dictionary

You can set up the SDK to load your feature flag & setting overrides from a dictionary.

dictionary = {
'enabledFeature': True,
'disabledFeature': False,
'intSetting': 5,
'doubleSetting': 3.14,
'stringSetting': 'test'
}

client = configcatclient.get('#YOUR-SDK-KEY#',
ConfigCatOptions(
flag_overrides=LocalDictionaryFlagOverrides(source=dictionary, override_behaviour=OverrideBehaviour.LocalOnly)
)
)

Logging

The ConfigCat SDK uses Python's built-in logging library.

With the logging.basicConfig() method, you can set up the logging system. The following example shows how to set the default root logger to write logs to the standard output with INFO log level.

import logging
logging.basicConfig(level=logging.INFO)

The ConfigCat SDK specifies an internal logger called 'configcat'. The following example shows how to set the Log Level on the internal ConfigCat logger.

logger = logging.getLogger('configcat')
logger.setLevel(logging.INFO)

Available log levels:

LevelDescription
ERROROnly error level events are logged.
WARNDefault. Errors and Warnings are logged.
INFOErrors, Warnings and feature flag evaluation is logged.
DEBUGAll of the above plus debug info is logged. Debug logs can be different for other SDKs.

Info level logging helps to inspect the feature flag evaluation process:

INFO:configcat:[5000] Evaluating 'isPOCFeatureEnabled' for User '{"Identifier":"<SOME USERID>","Email":"[email protected]","Country":"US","SubscriptionType":"Pro","Role":"Admin","version":"1.0.0"}'
Evaluating targeting rules and applying the first match if any:
- IF User.Email CONTAINS ANY OF ['@something.com'] THEN 'False' => no match
- IF User.Email CONTAINS ANY OF ['@example.com'] THEN 'True' => MATCH, applying rule
Returning 'True'.

get_all_keys()

You can query the keys from your config JSON in the SDK with the get_all_keys() method.

client = configcatclient.get('#YOUR-SDK-KEY#')
keys = client.get_all_keys()

get_all_values()

Evaluates and returns the values of all feature flags and settings. Passing a User Object is optional.

ParametersDescription
userOptional, User Object. Essential when using Targeting. Read more about Targeting.
client = configcatclient.get('#YOUR-SDK-KEY#')
all_values = client.get_all_values(User('#UNIQUE-USER-IDENTIFIER#')) # Optional User Object

get_all_value_details()

Evaluates and returns the detailed values of all feature flags and settings. Passing a User Object is optional.

client = configcatclient.get('#YOUR-SDK-KEY#')
all_value_details = client.get_all_value_details(User('#UNIQUE-USER-IDENTIFIER#')) # Optional User Object

Custom cache

The ConfigCat SDK stores the downloaded config data in a local cache to minimize network traffic and enhance client performance. If you prefer to use your own cache solution, such as an external or distributed cache in your system, you can implement the ConfigCache interface and set the config_cache parameter in the options passed to configcatclient.get. This allows you to seamlessly integrate ConfigCat with your existing caching infrastructure.

from configcatclient.interfaces import ConfigCache

class InMemoryConfigCache(ConfigCache):
def __init__(self):
self._value = {}

def get(self, key):
# you should return the cached value
return self._value.get(key)

def set(self, key, value):
# you should cache the new value
self._value[key] = value

Then use your custom cache implementation:

client = configcatclient.get('#YOUR-SDK-KEY#',
ConfigCatOptions(
config_cache=InMemoryConfigCache()
)
)
info

The Python SDK supports shared caching. You can read more about this feature and the required minimum SDK versions here.

Using ConfigCat behind a proxy

Provide your own network credentials (username/password), and proxy server settings (proxy server/port) by passing the proxy details to the creator method.

proxies = {'https': '127.0.0.1:8080'}
proxy_auth = HTTPProxyAuth('user', 'password')
client = configcatclient.get('#YOUR-SDK-KEY#',
ConfigCatOptions(
proxies=proxies,
proxy_auth=proxy_auth
)
)

Sample Applications

Guides

See this guide on how to use ConfigCat's Python SDK in a Flask application.

Look under the hood