DAP event

CUSP

Writing Idiomatic Python;

Python Packaging;

Static Website Generator;

-Mohit Sharma

meet.ps/cusp-edap

http://slides.com/mohitsharma44/deck/live

Idiomatic python

Why ?

>>> import this

How ?

Stay tuned...

Always code as if the guy who ends up maintaining your code will be a violent psychopath who knows where you live.

- John Woods

Lets get started..

A Word of Advice

if language == "Python" or language == "Shell" or language == "Java" or language == "C++":
    print("""
 For the brave souls who get this far: You are the chosen ones,
 the valiant knights of programming.
""")

if language in ("Python", "Shell", "Java", "C++"):
    print("""
 For the brave souls who get this far: You are the chosen ones,
 the valiant knights of programming.
""")

Multiple Condition Checking

def some_useful_print_function(car):
    return "Company: "+car.company + "Name: "+car.name + \
        "Type: "+car.type + "Year: "+car.year + "Price: "\
        +car.price

def some_useful_print_function(car):
    return "Company: %s " + "Name: %s "+ "Type: %s " + "Year: %d " +\
        "Price: %f " %(car.company, car.name, car.type, car.year, 
         car.price)

def some_useful_print_function(car):
    return "Company: {vehicle.company} " + "Name: {vehicle.name} "+ \
        "Type: {vehicle.type} " + "Year: {vehicle.year} " + \
        "Price: {vehicle.price} ".format(vehicle=car)

result = None
for value in values:
    if acceptable(value):
        result = value 
        break    
if not result:
    raise ValueError("No acceptable language found!")

result = None
for value in values:
    if acceptable(value):
        result = value 
        break    
else:
    raise ValueError("No acceptable language found!")

for ... else

for i in range(1000000):
    ...

for i in xrange(1000000):
    ...

Looping over range of numbers

fruits = ["apples", "mangoes", "banana"]

for i in range(len(fruits)):
    print fruits[i]

fruits = ["apples", "mangoes", "banana"]
for fruit in fruits:
    print fruit

Looping over a collection

fruits = ["apples", "mangoes", "banana"]

for i in range(len(fruits)):
    print i, ' = ', fruits[i]

fruits = ["apples", "mangoes", "banana"]

for i, fruit in enumerate(fruits):
    print i, ' = ', fruit

Looping over collection and indices

Looping over two collections

colors = ["red", "blue", "green", "yellow"]
fruits = ["apples", "mangoes", "banana"]

# Take min of two collections and loop over the smallest:
n = min(len(colors), len(fruits))
for i in range(n):
    print fruits[i], " = ", colors[i]

# It creates a 3rd list that consists of tuples 
# which consists its own set of objects 
# that points back to the actual list
for fruit, color in zip(fruits, colors):
    print fruit, " = ", color

# iterator for zip
from itertools import izip
for fruit, color in izip(fruits, colors):
    print fruit, " = ", color

fruits = ["apples", "mangoes", "banana"]

for fruit in sorted(fruits):
    print fruit

# Reversed
for fruit in sorted(fruits, reverse=True):
  print fruit

fruits = ["apples", "mangoes", "banana"]

# In place list sorting
fruit.sort()

# Reversed
fruit.sort(reverse=True)

sorting a list

fruits = ["apples", "mangoes", "banana"]

result = ""
for fruit in fruits:
    result += fruit + " "

fruits = ["apples", "mangoes", "banana"]

result = " ".join(fruits)

String from a List

fruits = ["apples", "mangoes", "banana"]

fruit = "apples"
if fruit not in fruits:
    fruits.append(fruit)

fruits = set(["apples", "mangoes", "banana"])

fruit = "apples"
fruits.append(fruit)

Sets

fruits = ["apples", "mangoes", "banana"]

fruit = "apples"
if fruit not in fruits:
    fruits.append(fruit)

fruits = set(["apples", "mangoes", "banana"])

fruit = "apples"
fruits.append(fruit)

Sets

# Removing an element
for k in d.keys():
  if k.startswith('r'):
    del d[k]

d = {k: d[k] for k in d if not k.startswith('r')}

Looping over dictionary keys

d = dict(izip(fruits, colors))

Construct a dictionary from multiple sequences

from collections import defaultdict

colors = ["red", "blue", "green", "yellow"]
d = defaultdict(int)
for color in colors:
    d[name] += 1

Counting in dictionaries

from collections import defaultdict

colors = ["red", "blue", "green", "amber", "gray"]
d = defaultdict(list)
for color in colors:
    key = len(color)
    d[key].append(color)

Grouping in dictionaries

try:
    os.remove('somefile.tmp')
except OSError, e:
    print "Watchout, Man! \n"+str(e)

@contextmanager
def ignored(*exception):
    try:
      yield
    except exception, e:
      print "Watchout, Man! \n"+str(e)

with ignored(OSError):
    os.remove('somefile.tmp')

Context Managers

# List Comprehension
sum([i**2 for i in xrange(10)])

# List Comprehension
sum(i**2 for i in xrange(10))

Generator Expressions

A word of Caution

# Dear maintainer:
# Once you are done trying to 'optimize' this 
# routine,and have realized what a terrible
# mistake that was, please increment the
# following counter as a warning to the next 
# guy:
#
# total_hours_wasted_here = 42

Premature optimization is the root of all evil

Python Packaging

from init to deploy

...made easy

Setting up your environment

* Project X requires numpy v1.5.0 because it is using

numpy.refft

* Project Y requires numpy v1.6.0 because it is using

numpy.fft

* Install packages without root privileges.

Virtualenv !!!

Setting up your environment

$ mkdir venv
$ virtualenv venv

* Install virtualenv

$ pip install virtualenv

* Create a virtual environment

$ source venv/bin/activate

* Activate virtualenv

(venv)$ deactivate

* Restore environment

* Check your installed packages

$ pip freeze

Structure of a python package

my_package

setup.py

my_package

tests

docs

__init__.py

test_module1.py

conf.py

subpackage

module1.py

Pyscaffold

* Install pyscaffold

(venv)$ pip install pyscaffold

* You can also install a particular version (optional)

(venv)$ pip install "pyscaffold>=2.4"

* Install sphinx

(venv)$ pip install sphinx

Time for demo!

Generating Static Website

Pelican

(venv)$ pelican-quickstart

* Install markdown

(venv)$ pip install markdown

* quickstart

* Install pelican

(venv)$ pip install pelican

first_post
##########

:date: 2016-04-21 13:32
:category: Test

Hello World from Pelican!

* Your first post

> Where do you want to create your new web site? [.] 
> What will be the title of this web site? cusp-edap
> Who will be the author of this web site? mohit
> What will be the default language of this web site? [en] 
> Do you want to specify a URL prefix? e.g., http://example.com   (Y/n) 
> What is your URL prefix? (see above example; no trailing slash) http://localhost:8000
> Do you want to enable article pagination? (Y/n) 
> How many articles per page do you want? [10] 
> What is your time zone? [Europe/Paris] America/NewYork
Please enter a valid time zone:
 (check [http://en.wikipedia.org/wiki/List_of_tz_database_time_zones])
> What is your time zone? [Europe/Paris] America/New York
> Do you want to generate a Fabfile/Makefile to automate generation and publishing? (Y/n) n
> Do you want an auto-reload & simpleHTTP script to assist with theme and site development? (Y/n)

* Questionaire

Publishing on github pages

* Remove all files from the old working tree

(venv)$ git rm -rf .

* copy output to gh-pages branch, commit and push

* checkout another branch

(venv)$ git checkout --orphan gh-pages

* Checkout to master and merge gh-pages

(venv)$ git checkout master
(venv)$ git merge gh-pages
(venv)$ git push origin master