Popular recipes by Andrey Nikishaev

Decorator to check if needed modules for method are imported (Python)

2014-03-18T14:11:20-07:00

Python recipe 578852 by Andrey Nikishaev (decorator, import).

Check if needed modules imported before run method

Example::

    @require_module(['time'],exception=Exception)
    def get_time():
        return time.time()

Decorator to check method param types (Python)

2014-01-14T11:23:40-08:00

Python recipe 578809 by Andrey Nikishaev (decorators, method, typecheck).

This solution give possibility to check method param type, raise needed exception type, and also have good readability in the decorator definition.

Script for cache invalidation at Amazon CloudFront (Python)

2011-07-05T14:40:58-07:00

Python recipe 577779 by Andrey Nikishaev (amazon, cloudfront).

This script scans directories that was uploaded to CloudFront and build files index. When you modify some files, script automatically see what files was modified since the last update, and clear cache on CloudFront only for them.

Usage: script.py data_dir [index_file] [dir_prefix]

data_dir - path to directory with uploaded data

index_file - path to files index

dir_prefix - needed if you data_dir path is different from url at CloudFront.For example: Your data_dir is '/data' but url at CloudFront is http://url.com/social/data/ so dir_prefix will be '/social/data/'

Linux cat command backward (Python)

2011-05-18T12:54:15-07:00

Python recipe 577699 by Andrey Nikishaev (cat, linux, log, output). Revision 2.

Utility to output file from backward. Useful for logs output.

Simple local cache and cache decorator (Python)

2010-12-08T09:06:34-08:00

Python recipe 577492 by Andrey Nikishaev (cache, decorator, memoization, python).

Simple local cache. It saves local data in singleton dictionary with convenient interface

Examples of use:

# Initialize
SimpleCache({'data':{'example':'example data'}})
# Getting instance
c = SimpleCache.getInstance()

c.set('re.reg_exp_compiled',re.compile(r'\W*'))
reg_exp = c.get('re.reg_exp_compiled',default=re.compile(r'\W*'))

# --------------------------------------------------------------

c = SimpleCache.getInstance()
reg_exp = c.getset('re.reg_exp_compiled',re.compile(r'\W*'))

# --------------------------------------------------------------    

@scache
def func1():
    return 'OK'

MongoDB Pool for gevent and pymongo packages (Python)

2011-09-02T05:56:58-07:00

Python recipe 577490 by Andrey Nikishaev (gevent, mongodb, pymongo, python). Revision 2.

Wrote some simple implementation of pool for pymongo package under gevent coroutine library.

Base bug here was with pymongo.connection.Pool because in the original package it is thread-local, so when you spawn new greenlet and trying to get already open connection, it creates new connection because in this greenlet pool is empty. So if you will implement your own pool don’t forget about this.

Example of use:

# Create Pool. 
db = Mongo('test_db',10)
# Get connection from pool
conn = db.get_conn()
# Get raw connection for GridFS
raw_conn = conn.getDB

#Mongo is a singleton. So if you want to get connection in another part of application just type
db = Mongo()
conn = db.get_conn()

#Connection will get back to pool when context will be closed.

Observer Design Pattern for python gevent coroutine package (Python)

2010-12-08T08:33:30-08:00

Python recipe 577491 by Andrey Nikishaev (event, gevent, observer, python).

This is simple implementation of the observer design pattern. Acting as a registration hub, it fires events when requested. Also i have gevent.Timeout like interface in situations when you need to run event-method in the same greenlet. Example:

e = Observer()
ev = e.wait('kill')
try:
    gevent.sleep(3)
except FiredEvent:
    print 'Fired!'
else:
    print 'Not Fired!'
finally:
    ev.cancel()

But rememeber, if you are using subscribe method, event-method will be executed in another greenlet.