Alex Buzunov pydemo

The problem with comprehention is that for every list comprehension, we are allocating a new list, increasing memory usage. Instead of using list comprehension, we can employ generators. Generators are objects that, when iterated upon, compute a value on the fly and return the result.

def map_comprehension(numbers):
    a = [n * 2 for n in numbers]
    b = [n ** 2 for n in a]
    c = [n ** 0.33 for n in b]
 return max(c)

Faster array retrieval - numpy.take David M. Cooke wrote a package called numexpr it is based on a single function--numexpr.evaluate.

a = np.random.rand(10000) 
b = np.random.rand(10000) 
c = np.random.rand(10000)

d = ne.evaluate('a + b * c')

%%cython 
cdef double a 
from libc.stdio cimport printf 
printf("%p", &a)
# Output:
# 0x7fc8bb611210

PyPy warning about timeit

$ source my-pypy-env/bin/activate
Python 2.7.12 (aff251e54385, Nov 09 2016, 18:02:49)
[PyPy 5.6.0 with GCC 4.8.2]

(my-pypy-env) $ python -m timeit --setup "from simul import benchmark" "benchmark()"
WARNING: timeit is a very unreliable tool. use perf or something else for real measurements
10 loops, average of 7: 106 +- 0.383 msec per loop (using standard deviation)

import threading

def wait_and_print_async(msg):
    def callback():
        print(msg)

    timer = threading.Timer(1.0, callback)
    timer.start()

Futures are fancier callbacks

    they keep track of the resource status
    cancel(unschedule) schedled tasks
    handle exceptions more naturally

from concurrent.futures import Future

def network_request_async(number):

f-strings (in Python 3.6+):

In [8]: decksize = 52
 
In [9]: print(f'There are {factorial(decksize):g} ways to shuffle {decksize} cards')
There are 8.06582e+67 ways to shuffle 52 cards

Coroutine as a function that can be stopped and resumed.

A basic example of coroutines is generators.

Generators can be defined in Python using the yield statement inside a function.

 def range_generator(n):
 i = 0

Philly was a cool place to grow up and live in. The transportation system is awesome ( compared to many other cities in the U.S. ) and you can just about get anywhere with transfers and time. The museums in center city are legendary as is the center city library ( and all of the Free Library branches every where in the city ) —- Fairmount Park is one of the largest city parks in the world and you can ( truthfully ) spend weeks exploring it from the 17th century Swedes cabins in the North end of the park, to the covered bridge, the 18th century road and the Valley Green Inn to the hermits cave and the East Falls, the trails throughout the park and just the boreal forest surroundings. Manyunk is so cool with it’s Paris like neighborhood as is The Italian neighborhoods around South Philly and its’ market —- Society Hill and it’s streets of charming 18th century houses makes a wonderful walk as does the Antique Shops on Pine Street, Freeman’s Auction House on Chestnut Street has some really cool Tuesday auctions

	#!/usr/bin/env bash

	# FeedTube, a feed video downloader for Youtube
	# Copyright Carlos Fenollosa <cf@cfenollosa.com>, 2018. Licensed under the GNU GPL v3: https://www.gnu.org/licenses/gpl-3.0.en.html
	# Check out README.md for more details

	# Manual switches. Possible values are "yes" or "" (empty)
	ASCII_ONLY="yes" # Output video filename will only contain ascii characters

	# Check help switch and show usage