User Guide

This section covers the main features of requests-cache.

Installation

Install with pip:

$ pip install requests-cache

Requirements

  • Requires python 3.6+.

  • You may need additional dependencies depending on which backend you want to use. To install with extra dependencies for all supported Cache Backends:

    $ pip install requests-cache[backends]

Optional Setup Steps

  • See Security for recommended setup steps for more secure cache serialization.

  • See Contributing Guide for setup steps for local development.

General Usage

There are two main ways of using requests-cache:

Sessions

CachedSession can be used as a drop-in replacement for requests.Session. Basic usage looks like this:

>>> from requests_cache import CachedSession
>>>
>>> session = CachedSession()
>>> session.get('http://httpbin.org/get')

Any requests.Session method can be used (but see HTTP Methods section below for config details):

>>> session.request('GET', 'http://httpbin.org/get')
>>> session.head('http://httpbin.org/get')

Caching can be temporarily disabled with CachedSession.cache_disabled():

>>> with session.cache_disabled():
...     session.get('http://httpbin.org/get')

The best way to clean up your cache is through Cache Expiration, but you can also clear out everything at once with BaseCache.clear():

>>> session.cache.clear()

Patching

In some situations, it may not be possible or convenient to manage your own session object. In those cases, you can use install_cache() to add caching to all requests functions:

>>> import requests
>>> import requests_cache
>>>
>>> requests_cache.install_cache()
>>> requests.get('http://httpbin.org/get')

As well as session methods:

>>> session = requests.Session()
>>> session.get('http://httpbin.org/get')

install_cache() accepts all the same parameters as CachedSession:

>>> requests_cache.install_cache(expire_after=360, allowable_methods=('GET', 'POST'))

It can be temporarily enabled():

>>> with requests_cache.enabled():
...     requests.get('http://httpbin.org/get')  # Will be cached

Or temporarily disabled():

>>> requests_cache.install_cache()
>>> with requests_cache.disabled():
...     requests.get('http://httpbin.org/get')  # Will not be cached

Or completely removed with uninstall_cache():

>>> requests_cache.uninstall_cache()
>>> requests.get('http://httpbin.org/get')

You can also clear out all responses in the cache with clear(), and check if requests-cache is currently installed with is_installed().

Limitations

Like any other utility that uses global patching, there are some scenarios where you won’t want to use install_cache():

  • In a multi-threaded or multiprocess application

  • In an application that uses other packages that extend or modify requests.Session

  • In a package that will be used by other packages or applications

Cache Backends

Several cache backends are included, which can be selected with the backend parameter for either CachedSession or install_cache():

  • 'sqlite': SQLite database (default)

  • 'redis': Redis cache (requires redis)

  • 'mongodb': MongoDB database (requires pymongo)

  • 'gridfs': GridFS collections on a MongoDB database (requires pymongo)

  • 'dynamodb': Amazon DynamoDB database (requires boto3)

  • 'memory' : A non-persistent cache that just stores responses in memory

A backend can be specified either by name, class or instance:

>>> from requests_cache.backends import RedisCache
>>> from requests_cache import CachedSession
>>>
>>> # Backend name
>>> session = CachedSession(backend='redis', namespace='my-cache')

>>> # Backend class
>>> session = CachedSession(backend=RedisCache, namespace='my-cache')

>>> # Backend instance
>>> session = CachedSession(backend=RedisCache(namespace='my-cache'))

See requests_cache.backends for more backend-specific usage details, and see Custom Backends for details on creating your own implementation.

Cache Name

The cache_name parameter will be used as follows depending on the backend:

  • sqlite: Database path, e.g ~/.cache/my_cache.sqlite

  • dynamodb: Table name

  • mongodb and gridfs: Database name

  • redis: Namespace, meaning all keys will be prefixed with '<cache_name>:'

Cache Options

A number of options are available to modify which responses are cached and how they are cached.

HTTP Methods

By default, only GET and HEAD requests are cached. To cache additional HTTP methods, specify them with allowable_methods. For example, caching POST requests can be used to ensure you don’t send the same data multiple times:

>>> session = CachedSession(allowable_methods=('GET', 'POST'))
>>> session.post('http://httpbin.org/post', json={'param': 'value'})

Status Codes

By default, only responses with a 200 status code are cached. To cache additional status codes, specify them with allowable_codes”

>>> session = CachedSession(allowable_codes=(200, 418))
>>> session.get('http://httpbin.org/teapot')

Request Parameters

By default, all request parameters are taken into account when caching responses. In some cases, there may be request parameters that don’t affect the response data, for example authentication tokens or credentials. If you want to ignore specific parameters, specify them with ignored_parameters:

>>> session = CachedSession(ignored_parameters=['auth-token'])
>>> # Only the first request will be sent
>>> session.get('http://httpbin.org/get', params={'auth-token': '2F63E5DF4F44'})
>>> session.get('http://httpbin.org/get', params={'auth-token': 'D9FAEB3449D3'})

Request Headers

By default, request headers are not taken into account when caching responses. In some cases, different headers may result in different response data, so you may want to cache them separately. To enable this, use include_get_headers:

>>> session = CachedSession(include_get_headers=True)
>>> # Both of these requests will be sent and cached separately
>>> session.get('http://httpbin.org/headers', {'Accept': 'text/plain'})
>>> session.get('http://httpbin.org/headers', {'Accept': 'application/json'})

Cache Expiration

By default, cached responses will be stored indefinitely. You can initialize the cache with an expire_after value to specify how long responses will be cached.

Expiration Types

expire_after can be any of the following:

Examples:

>>> # Set expiration for the session using a value in seconds
>>> session = CachedSession(expire_after=360)

>>> # To specify a different unit of time, use a timedelta
>>> from datetime import timedelta
>>> session = CachedSession(expire_after=timedelta(days=30))

>>> # Update an existing session to disable expiration (i.e., store indefinitely)
>>> session.expire_after = -1

Expiration Scopes

Passing expire_after to CachedSession will set the expiration for the duration of that session. Expiration can also be set on a per-URL or per-request basis. The following order of precedence is used:

  1. Per-request expiration (expire_after argument for CachedSession.request())

  2. Per-URL expiration (urls_expire_after argument for CachedSession)

  3. Per-session expiration (expire_after argument for CachedSession)

To set expiration for a single request:

>>> session.get('http://httpbin.org/get', expire_after=360)

URL Patterns

You can use urls_expire_after to set different expiration values for different requests, based on URL glob patterns. This allows you to customize caching based on what you know about the resources you’re requesting. For example, you might request one resource that gets updated frequently, another that changes infrequently, and another that never changes. Example:

>>> urls_expire_after = {
...     '*.site_1.com': 30,
...     'site_2.com/resource_1': 60 * 2,
...     'site_2.com/resource_2': 60 * 60 * 24,
...     'site_2.com/static': -1,
... }
>>> session = CachedSession(urls_expire_after=urls_expire_after)

Notes:

  • urls_expire_after should be a dict in the format {'pattern': expire_after}

  • expire_after accepts the same types as CachedSession.expire_after

  • Patterns will match request base URLs, so the pattern site.com/resource/ is equivalent to http*://site.com/resource/**

  • If there is more than one match, the first match will be used in the order they are defined

  • If no patterns match a request, CachedSession.expire_after will be used as a default.

Removing Expired Responses

For better performance, expired responses won’t be removed immediately, but will be removed (or replaced) the next time they are requested. To manually clear all expired responses, use CachedSession.remove_expired_responses():

>>> session.remove_expired_responses()

Or, when using patching:

>>> requests_cache.remove_expired_responses()

You can also apply a different expire_after to previously cached responses, which will revalidate the cache with the new expiration time:

>>> session.remove_expired_responses(expire_after=timedelta(days=30))

Potential Issues

  • Version updates of requests, urllib3 or requests-cache itself may not be compatible with previously cached data (see issues #56 and #102). The best way to prevent this is to use a virtualenv and pin your dependency versions.

  • See Security for notes on serialization security