poros

# USAGE
@track_entry_and_exit('widget loader')
def activity():
    print('Some time consuming activity goes here')
    load_widget()

with track_entry_and_exit('widget loader'):
    print('Some time consuming activity goes here')
    load_widget()

poros

from contextlib import contextmanager

@contextmanager
def connect_to_db(address):
    db = CrappyDBConnection(address)
    try:
        yield db
    except ConnectionError:
        logging.exception('Connection dropped')
        db.cleanup('rollback')

poros

class DBConnection(object):
    def __init__(self, address):
        self.crappy_db = CrappyDBConnection(address)
    
    def __enter__(self):
        self.crappy_db.connect()
        return self  # what is returned here will be availabe via "as"
    
    def __exit__(self, exc_type, exc_val, exc_tb):
        if exc_type == ConnectionError:

poros

from multiprocessing import Pool

pool = Pool(4)
results = pool.map(urllib2.urlopen, urls)
pool.close() 
pool.join() 


# if you want threads instead of processes
from multiprocessing.dummy import Pool

poros

try:
    os.remove('somefile.tmp')
except OSError:
    pass

# note: checking if the file exists before deletion leads to a race condition

# PYTHON 3
from contextlib import suppress

poros

saved = {}

def web_lookup(url):
    if url in saved:
        return saverd[url]
    page = urrlib.urlopen(url).read()
    saved[url] = page
    return page

# NEEDS TO BE A PURE FUNCTION, NO SIDE EFFECTS LIKE PRINT

poros

def fibonacci(n):
    x = 0
    y = 1
    for i in range(n):
        print x
        tmp = y
        y = x + y
        x = tmp

poros

d = defaults.copy()
d.update(os.environ)
d.update(command_line_arguments)

# PYTHON3 ONLY!!!
from collections import ChainMap
d = ChainMap(command_line_arguments, os.environ, defaults)

# it's view, not a real dictionary. if you want something equivalent to a new one
d = ChainMap({}, command_line_arguments, os.environ, defaults)

poros

colors = ['green', 'blue', 'green', 'red', 'blue', 'green']

d = {}
for color in colors:
    if color not in d:
        d[color] = 0
    d[color] += 1


# slighlty better

poros

d = {}
for name in names:
    key = len(name)
    if key not in d:
        d[key] = []
    d[key].append(name)


# slightly better
d = {}