User Guide

This section covers the main features of requests-cache.

Installation

Install with pip:

pip install requests-cache

Or with Conda, if you prefer:

conda install -c conda-forge 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)

  • 'filesystem': Stores responses as files on the local filesystem

  • '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>:'

  • filesystem: Cache directory

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'})

In addition to allowing the cache to ignore these parameters when fetching cached results, these parameters will also be removed from the cache data, including in the request headers. This makes ignored_parameters a good way to prevent key material or other secrets from being saved in the cache backend.

Request Headers

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. There are a number of options for specifying how long to store responses. The simplest option is to initialize the cache with an expire_after value:

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

Expiration Precedence

Expiration can be set on a per-session, per-URL, or per-request basis, in addition to cache headers (see sections below for usage details). When there are multiple values provided for a given request, the following order of precedence is used:

  1. Cache-Control request headers (if enabled)

  2. Cache-Control response headers (if enabled)

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

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

  5. Per-session expiration (expire_after argument for CacheBackend)

Expiration Values

expire_after can be any of the following:

  • -1 (to never expire)

  • 0 (to “expire immediately,” e.g. bypass the cache)

  • A positive number (in seconds)

  • A timedelta

  • A datetime

Examples:

> >>> # To specify a unit of time other than seconds, 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
>
> >>> # Disable caching by default, unless enabled by other settings
> >>> session = CachedSession(expire_after=0)

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)

You can also use this to define a cache whitelist, so only the patterns you define will be cached:

>>> urls_expire_after = {
...     '\*.site_1.com': 30,
...     'site_2.com/static': -1,
...     '\*': 0,  # Every other non-matching URL: do not cache
... }

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.

Cache-Control

Warning

This is not intended to be a thorough or strict implementation of header-based HTTP caching, e.g. according to RFC 2616.

Optional support is included for a simplified subset of Cache-Control and other cache headers in both requests and responses. To enable this behavior, use the cache_control option:

>>> session = CachedSession(cache_control=True)

Supported request headers:

  • Cache-Control: max-age: Used as the expiration time in seconds

  • Cache-Control: no-cache: Skips reading response data from the cache

  • Cache-Control: no-store: Skips reading and writing response data from/to the cache

Supported response headers:

  • Cache-Control: max-age: Used as the expiration time in seconds

  • Cache-Control: no-store Skips writing response data to the cache

  • Expires: Used as an absolute expiration time

Notes:

  • Unlike a browser or proxy cache, max-age=0 does not currently clear previously cached responses.

  • If enabled, Cache-Control directives will take priority over any other expire_after value. See Expiration Precedence for the full order of precedence.

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))

Serializers

By default, responses are serialized using pickle. Some other options are also available:

Note

These features require python 3.7+ and additional dependencies

JSON Serializer

Storing responses as JSON gives you the benefit of making them human-readable and editable, in exchange for a slight reduction in performance. This can be especially useful in combination with the filesystem backend.

Example JSON-serialized Response

{
  "url": "https://httpbin.org/get",
  "status_code": 200,
  "reason": "OK",
  "_content": "dkP>RB4Ki8b0Rt*dwnb*3LqdNXk}q!WpZ;OIv{%rARr(hB0*zgWpH#NIv^q{FDfD|APOKLARr<^V`F7-bS*`0V{c?>Zf7DoAR=daX>cqcWMyV-VRU68EFcOXARr(jNN;m=B03-<XmoUNVrgzJZ*pfMEFcOXARr(jRdZ!>EkS2xZge6#AR=&ibZBpGEplaXb!BsOb1yP3GBz$SA}k;ZARr(hB3La!ZF+7kRB~ZsWi3f$B03-<Qg3f`JuxjdFlIPmF)(2*GB7hXGcjZ_Gh<>hGc{o{G%#g2VK_22A_^cNeJmgfARr=da%pF2ZX!A$A~82JE-^VSF*GqQGBq+HEFcOXAR={gY$7@!B4~7UaC15@FKBdhaAIk0E^l&YFK1<RA_{#9",
  "cache_key": "4dc151d95200ec91fa77021989f5194e9be47e87f8f228306f3a8d5434b9e547",
  "created_at": "2021-07-21T22:34:50.343095",
  "elapsed": 0.242198,
  "encoding": "utf-8",
  "headers": {
    "Date": "Wed, 21 Jul 2021 22:34:50 GMT",
    "Content-Type": "application/json",
    "Content-Length": "308",
    "Connection": "keep-alive",
    "Server": "gunicorn/19.9.0",
    "Access-Control-Allow-Origin": "*",
    "Access-Control-Allow-Credentials": "true"
  },
  "request": {
    "body": "PH%2y",
    "headers": {
      "User-Agent": "python-requests/2.26.0",
      "Accept-Encoding": "gzip, deflate",
      "Accept": "*/*",
      "Connection": "keep-alive"
    },
    "method": "GET",
    "url": "https://httpbin.org/get"
  },
  "raw": {
    "decode_content": false,
    "reason": "OK",
    "status": 200,
    "version": 11
  }
}

You can install the extra dependencies for this serializer with:

pip install requests-cache[json]

YAML Serializer

YAML is another option if you need a human-readable/editable format, with the same tradeoffs as JSON.

Example YAML-serialized Response

url: https://httpbin.org/get
status_code: 200
reason: OK
_content: !!binary |
  ewogICJhcmdzIjoge30sIAogICJoZWFkZXJzIjogewogICAgIkFjY2VwdCI6ICIqLyoiLCAKICAg
  ICJBY2NlcHQtRW5jb2RpbmciOiAiZ3ppcCwgZGVmbGF0ZSIsIAogICAgIkhvc3QiOiAiaHR0cGJp
  bi5vcmciLCAKICAgICJVc2VyLUFnZW50IjogInB5dGhvbi1yZXF1ZXN0cy8yLjI2LjAiLCAKICAg
  ICJYLUFtem4tVHJhY2UtSWQiOiAiUm9vdD0xLTYwZjhhMDcxLTBiN2JmN2VjNGMyZTdmNjA2YWI4
  ZDYyNCIKICB9LCAKICAib3JpZ2luIjogIjE3My4xOS4xNDEuMjUyIiwgCiAgInVybCI6ICJodHRw
  czovL2h0dHBiaW4ub3JnL2dldCIKfQo=
cache_key: 4dc151d95200ec91fa77021989f5194e9be47e87f8f228306f3a8d5434b9e547
created_at: '2021-07-21T22:32:17.592974'
elapsed: 0.187586
encoding: utf-8
headers:
  Access-Control-Allow-Credentials: 'true'
  Access-Control-Allow-Origin: '*'
  Connection: keep-alive
  Content-Length: '308'
  Content-Type: application/json
  Date: Wed, 21 Jul 2021 22:32:17 GMT
  Server: gunicorn/19.9.0
request:
  method: GET
  url: https://httpbin.org/get
  body: !!binary |
    Tm9uZQ==
  headers:
    Accept: '*/*'
    Accept-Encoding: gzip, deflate
    Connection: keep-alive
    User-Agent: python-requests/2.26.0
raw:
  decode_content: false
  reason: OK
  status: 200
  version: 11

You can install the extra dependencies for this serializer with:

pip install requests-cache[yaml]

BSON Serializer

BSON is a serialization format originally created for MongoDB, but it can also be used independently. Compared to JSON, it has better performance (although still not as fast as pickle), and adds support for additional data types. It is not human-readable, but some tools support reading and editing it directly (for example, bson-converter for Atom).

You can install the extra dependencies for this serializer with:

pip install requests-cache[mongo]

Or if you would like to use the standalone BSON codec for a different backend, without installing MongoDB dependencies:

pip install requests-cache[bson]

Error Handling

In some cases, you might cache a response, have it expire, but then encounter an error when retrieving a new response. If you would like to use expired response data in these cases, use the old_data_on_error option:

>>> # Cache a test response that will expire immediately
>>> session = CachedSession(old_data_on_error=True)
>>> session.get('https://httpbin.org/get', expire_after=0.001)
>>> time.sleep(0.001)

Afterward, let’s say the page has moved and you get a 404, or the site is experiencing downtime and you get a 500. You will then get the expired cache data instead:

>>> response = session.get('https://httpbin.org/get')
>>> print(response.from_cache, response.is_expired)
True, True

In addition to error codes, old_data_on_error also applies to exceptions (typically a RequestException). See requests documentation on Errors and Exceptions for more details on request errors in general.

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