atm: Get/Cache

atm is a simple wrapper for requests.get() that intelligently fetches data from the web and caches it locally or on Amazon S3. It's best used for web scraping projects where you want to avoid repeatedly requesting the source content. The inspiration for library came from a tutorial that @pudo gave at the 2013 Buenos Aires Hacks/Hackers Media Party.

Read the docs.

Install

$ pip install atm

Tests

$ nosetests tests

Usage

Set up a local cache:

from atm import ATM

teller = ATM('cache')
r = teller.get_cache('http://www.google.com/')

print teller.statement()

Set up a cache on Amazon S3:

Note: The bucket must already exist and and you must have AWS_ACCESS_KEY_ID and AWS_ACCESS_KEY_SECRET set as environmental variables.

Do this as follows:

$ export AWS_ACCESS_KEY_ID="myaccesskeyid"
$ export AWS_SECRET_ACCESS_KEY="myaccesskeysecret"

Now you're all set to cache results on S3:

from atm import ATM

teller = ATM('s3://my-bucket/path/to/cache/')
r = teller.get_cache('http://www.google.com/')

print teller.statement()

Set the file format as json (default = "txt"):

from atm import ATM

teller = ATM('cache', format="json")
r = teller.get_cache('https://www.healthcare.gov/what-is-the-health-insurance-marketplace.json')

print teller.statement()

Set an interval (in seconds) at which to update the cache. This option should be used when regularly polling static urls which have dynamic content.

from atm import ATM
import time

teller = ATM('cache', interval=10)

r = teller.get_cache('http://www.google.com/')
r = teller.get_cache('http://www.google.com/')

time.sleep(10)

content = teller.get_cache('http://www.google.com/')

print teller.statement()

Response Format

ATM.get_cache() returns an object with the following attributes:

• r.content = The content returned from the url or the cache.
• r.url = The url of content requested.
• r.filepath = The filepath of cache'd content.
• r.cache_dir = The directory of the cache'd content.
• r.bucket_name = The bucket name of this cache if the cache is located on S3.
• r.is_s3 = A boolean indicating whether the cache is located on S3.
• r.status_code = The status code of the response from reqeusts.get() if the content was not retrieved from the cache.
• r.source = The source of the content, either url or cache.
• r.timestamp = The bucketed timestamp of the request if an interval is specified when intializing ATM.

Convenience Methods

atm also comes with some convenience methods for working with cache'd content.

ATM.transaction(url, timestamp=None) returns the filepath in the cache for a url. If ATM has been initialized with a set interval, you can use the timestamp arg to look up the file in the cache associated with that timestamp.

ATM.withdraw(filepath) returns a the contents of a file in the cache, given it's filepath.

ATM.liquidate() returns a generator of the contents of all files in the cache.

ATM.statement() returns a list of filepaths in the cache.

ATM.default() deletes all files from the cache.