# User guide

## Installation

Install with pip or easy_install:

    pip install --upgrade requests-cache

or download latest version from version control:

    git clone git://github.com/reclosedev/requests-cache.git
    cd requests-cache
    python setup.py install

Warning

Version updates of `requests`, `urllib3` or `requests_cache` itself can break existing cache database (see https://github.com/reclosedev/requests-cache/issues/56 ). So if your code relies on cache, or is expensive in terms of time and traffic, please be sure to use something like `virtualenv` and pin your requirements.

## Usage

There is two ways of using `requests_cache`:

> - Using `CachedSession` instead `requests.Session`
> - Monkey patching `requests` to use `CachedSession` by default

Monkey-patching allows to add caching to existent program by adding just two lines:

Import `requests_cache` and call `install_cache()`

    import requests
    import requests_cache

    requests_cache.install_cache()

And you can use `requests`, all responses will be cached transparently!

For example, following code will take only 1-2 seconds instead 10:

    for i in range(10):
        requests.get('http://httpbin.org/delay/1')

Cache can be configured with some options, such as cache filename, backend (sqlite, mongodb, redis, memory), expiration time, etc. E.g. cache stored in sqlite database (default format) named `'test_cache.sqlite'` with expiration set to 300 seconds can be configured as:

    requests_cache.install_cache('test_cache', backend='sqlite', expire_after=300)

See also

Full list of options can be found in `requests_cache.install_cache()` reference

Transparent caching is achieved by monkey-patching `requests` library It is possible to uninstall this patch with `requests_cache.uninstall_cache()`.

Also, you can use `requests_cache.disabled()` context manager for temporary disabling caching:

    with requests_cache.disabled():
        print(requests.get('http://httpbin.org/ip').text)

If `Response` is taken from cache, `from_cache` attribute will be `True`:

    >>> import requests
    >>> import requests_cache
    >>> requests_cache.install_cache()
    >>> requests_cache.clear()
    >>> r = requests.get('http://httpbin.org/get')
    >>> r.from_cache
    False
    >>> r = requests.get('http://httpbin.org/get')
    >>> r.from_cache
    True

It can be used, for example, for request throttling with help of `requests` hook system:

    import time
    import requests
    import requests_cache

    def make_throttle_hook(timeout=1.0):
        """
        Returns a response hook function which sleeps for `timeout` seconds if
        response is not cached
        """
        def hook(response, *args, **kwargs):
            if not getattr(response, 'from_cache', False):
                print('sleeping')
                time.sleep(timeout)
            return response
        return hook

    if __name__ == '__main__':
        requests_cache.install_cache('wait_test')
        requests_cache.clear()

        s = requests_cache.CachedSession()
        s.hooks = {'response': make_throttle_hook(0.1)}
        s.get('http://httpbin.org/delay/get')
        s.get('http://httpbin.org/delay/get')

See also

example.py

Note

requests_cache prefetchs response content, be aware if your code uses streaming requests.

## Persistence

`requests_cache` designed to support different backends for persistent storage. By default it uses `sqlite` database. Type of storage can be selected with `backend` argument of `install_cache()`.

List of available backends:

- `'sqlite'` - sqlite database (default)
- `'memory'` - not persistent, stores all data in Python `dict` in memory
- `'mongodb'` - (experimental) MongoDB database (`pymongo < 3.0` required)
- `'redis'` - stores all data on a redis data store (`redis` required)

You can write your own and pass instance to `install_cache()` or `CachedSession` constructor. See Cache backends API documentation and sources.

## Expiration

If you are using cache with `expire_after` parameter set, responses are removed from the storage only when the same request is made. Since the store sizes can get out of control pretty quickly with expired items you can remove them using `remove_expired_responses()` or `BaseCache.remove_old_entries(created_before)`.

    expire_after = timedelta(hours=1)
    requests_cache.install_cache(expire_after=expire_after)
    ...
    requests_cache.remove_expired_responses()
    # or
    remove_old_entries.get_cache().remove_old_entries(datetime.utcnow() - expire_after)
    # when used as session
    session = CachedSession(..., expire_after=expire_after)
    ...
    session.cache.remove_old_entries(datetime.utcnow() - expire_after)

For more information see API reference.