Category: programming

Retry Decorator import time def retry(ExceptionToCheck, tries=4, delay=3, backoff=2): def deco_retry(f): def f_retry(*args, **kwargs): mtries, mdelay = tries, delay while mtries > 0: try: return f(*args, **kwargs) except ExceptionToCheck, e: print “%s, Retrying in %d seconds…” % (str(e), mdelay) time.sleep(mdelay) mtries -= 1 mdelay *= backoff lastException = e raise lastException return f_retry # true…

Singleton in Python import functools def singleton(cls): “”” Use class as singleton. “”” cls.__new_original__ = cls.__new__ @functools.wraps(cls.__new__) def singleton_new(cls, *args, **kw): it = cls.__dict__.get(‘__it__’) if it: return it cls.__it__ = it = cls.__new_original__(cls, *args, **kw) it.__init_original__(*args, **kw) return it cls.__new__ = singleton_new cls.__init_original__ = cls.__init__ cls.__init__ = object.__init__ return cls Sample use @singleton class Foo:…

Installation Install Qt4 # download http://qt.nokia.com/downloads/sdk-linux-x11-32bit-cpp-offline wget http://www.developer.nokia.com/dp?uri=http%3A%2F%2Fsw.nokia.com%2Fid%2F8ea74da4-fec1-4277-8b26-c58cc82e204b%2FQt_SDK_Lin32_offline chmod u+x ./QtSdk-offline-linux-x86-v1.2.1.run sudo ./QtSdk-offline-linux-x86-v1.2.1.run # install Qt4 Library sudo apt-get install -y python-lxml qt4-qmake Python Libraries # install cssselect – fix “ImportError: No module named cssselect” sudo pip install cssselect # install webkit-server git clone https://github.com/niklasb/webkit-server.git webkit-server cd webkit-server sudo python setup.py install # install dryscrape…

image_similarity.py # -*- coding: utf-8 -*- “”” Installation of needed libraries sudo apt-get install -y python-pip sudo pip install PIL numpy “”” import os, time, re, urllib from PIL import Image import logging format= ‘%(asctime)s – %(levelname)s – %(filename)s:%(lineno)s – %(funcName)s() – %(message)s’ format= ‘%(asctime)s – %(filename)s:%(lineno)s – %(message)s’ logging.basicConfig(level=logging.DEBUG, format=format) logger = logging.getLogger(__name__) def…

# -*- coding: utf-8 -*- from __future__ import print_function import time import sys import cPickle from time import strftime import inspect import traceback “”” Decorator Resources http://www.ellipsix.net/blog/2010/8/more-python-voodoo-optional-argument-decorators.html http://stackoverflow.com/questions/3931627/how-to-build-a-python-decorator-with-optional-parameters/3931903#3931903 http://typeandflow.blogspot.com/2011/06/python-decorator-with-optional-keyword.html http://pko.ch/2008/08/22/memoization-in-python-easier-than-what-it-should-be/ http://wiki.python.org/moin/PythonDecoratorLibrary#Memoize http://wiki.python.org/moin/PythonDecoratorLibrary#Asynchronous_Call http://code.activestate.com/recipes/496879-memoize-decorator-function-with-cache-size-limit/ “”” def main(): if True: pass return bb=”ten” aa=”wow” bigboy(bb, aa) def bigboy(tima, boo): y = “gee man” fooo(y) trace(msg=”great”) import datetime…

import os def dirsize(start_dirpath): total_size = 0 for dirpath, dirnames, filenames in os.walk(start_dirpath): for filename in filenames: filepath = os.path.join(dirpath, filename) total_size += os.path.getsize(filepath) return total_size

def hbytes(num): for x in [‘bytes’,’KB’,’MB’,’GB’]: if num < 1024.0: return "%3.1f%s" % (num, x) num /= 1024.0 return "%3.1f%s" % (num, 'TB')

def yield_file(filepath): with open(filepath, ‘r’) as f for line in f: yield line Usage: for line in yield_file(filepath): do_something(line) # whatever you want 🙂

Dictionaries 1. Unpythonic if b != None: a = b else: a = c 1. Pythonic a = b or c 1. Unpythonic if var is None: print(“var is not set”) 1. Pythonic if not var: print(“var is not set”) 1. Unpythonic print(“——————————“) 1. Pythonic print(“-“*30) Keys 1. Unpythonic mydict.has_key(key) 1. Pythonic key in mydict…