Python Idioms

PythonIdioms.py

__author__ = 'svalleru'

# Monkey patching
class Spam(object):
    def __init__(self, name):
        self._name = name

    def beans(self):
        print "Good morning, %s. Here are your delicious fried beans." % (self._name,)

s = Spam('Mrs. Higgs')
s.beans()

def beans_with_pepper(self):
    print "Hello, %s. Enjoy your fried beans with perpper" % (self._name,)
Spam.beans = beans_with_pepper  # monkey patch the class

s.beans()
# Good morning, Mrs. Higgs. Here are your delicious fried beans.
# Hello, Mrs. Higgs. Enjoy your fried beans with perpper
# ===

# List comprehensions
fruits = ['watermelon', 'apple', 'mango', 'kiwi', 'apricot', 'lemon', 'guava']
values = [2, 42, 18, 92, "boom", ['a', 'b', 'c']]
ufruits = [fruit.upper() for fruit in fruits]
afruits = [fruit for fruit in fruits if fruit.startswith('a')]
doubles = [v * 2 for v in values]

print "ufruits:", " ".join(ufruits)
print "afruits:", " ".join(afruits)
print "doubles:",
for d in doubles:
    print d,
# ufruits: WATERMELON APPLE MANGO KIWI APRICOT LEMON GUAVA
# afruits: apple apricot
# doubles: 4 84 36 184 boomboom ['a', 'b', 'c', 'a', 'b', 'c']
# ===

# More list comps
x, y, z, n = (int(input()) for _ in range(4))
print ([[a,b,c] for a in range(0,x+1) for b in range(0,y+1) for c in range(0,z+1) if a + b + c != n ])
#stdin: 
#1
#1
#1
#2
#stdout: [[0, 0, 0], [0, 0, 1], [0, 1, 0], [1, 0, 0], [1, 1, 1]]

# Sort with lambda key
fruits = ['watermelon', 'Apple', 'Mango', 'KIWI', 'apricot', 'LEMON', 'guava']
sfruits = sorted(fruits, key=lambda e: e.lower())
print " ".join(sfruits)
# Apple apricot guava KIWI LEMON Mango watermelon
d = {"keyword1": 3, "keyword2": 1, "keyword3": 5, "keyword4": 2}
print sorted(d, key=d.get, reverse=False)
# ['keyword2', 'keyword4', 'keyword1', 'keyword3']
# ===

# Decorator method
def debugger(old_func):
    def new_func(*args, **kwargs):
        print "*" * 40
        print "** function", old_func.__name__, "**"

        if args:
            print "\targs are ", args
        if kwargs:
            print "\tkwargs are ", kwargs

        print "*" * 40

        old_func(*args, **kwargs)  # call the 'real' function

    return new_func  # return the new function object

@debugger
def hello(greeting, whom):
    print "%s, %s" % (greeting, whom)

hello('hello', 'world')
hello('hi', 'Earth')
# ****************************************
# ** function hello **
# 	args are  ('hello', 'world')
# ****************************************
# hello, world
# ****************************************
# ** function hello **
# 	args are  ('hi', 'Earth')
# ****************************************
# hi, Earth
# ===

# Decorator class
class debugger(object):
    def __init__(self, phase=None, release=None):
        self._phase = phase
        self._release = release

    def __call__(self, oldf):
        def newf(*args, **kwargs):
            print
            print "*" * 40
            print "** function", oldf.__name__, "**"
            print "{0}: {1}".format(self._phase, self._release)
            print "*" * 40
            return oldf(*args, **kwargs)
        return newf

@debugger('phase I', 'FINAL')
def hello(greeting, whom):
    print "%s, %s" % (greeting, whom)

hello('hello', 'world')
hello('hi', 'Earth')
# ****************************************
# ** function hello **
# phase I: FINAL
# ****************************************
# hello, world
#
# ****************************************
# ** function hello **
# phase I: FINAL
# ****************************************
# hi, Earth
# ===

# Looping idioms
from itertools import izip

names = 'jack jim jill'.split()
colors = 'red blue yellow green'.split()

for name in names:
    print name.capitalize()
# Jack
# Jim
# Jill
for i, name in enumerate(names):
    print i, name.capitalize()
# 0 Jack
# 1 Jim
# 2 Jill
for name, color in zip(names, colors):
    print name, '-->', color
# jack --> red
# jim --> blue
# jill --> yellow
for name, color in izip(names, colors):
    print name, '-->', color
# jack --> red
# jim --> blue
# jill --> yellow
for name in reversed(names):
    print name
# jill
# jim
# jack
for name in sorted(names):
    print name
# jack
# jill
# jim
for name in sorted(names, key=len):
    print name
# jim
# jack
# jill
for name in sorted(names, reverse=True):
    print name
# jim
# jill
# jack
d = dict(izip(names, colors))
for name, color in d.iteritems():
    print name, '-->', color
# jim --> blue
# jack --> red
# jill --> yellow
# ===

# Sort a Dict based on value
from collections import OrderedDict

d = {v: v ** 2 for v in range(5)}
for k, v in OrderedDict(sorted(d.items(), key=lambda x: x[1], reverse=True)).iteritems():
    print k, v
# 4 16
# 3 9
# 2 4
# 1 1
# 0 0
# ===

# Dictionary comprehension
d = {v: v ** 2 for v in range(10)}
print d
# {0: 0, 1: 1, 2: 4, 3: 9, 4: 16, 5: 25, 6: 36, 7: 49, 8: 64, 9: 81}
# ===

# List indexes / List enumeration
l = ['0', '1', '2', '3', '4']
for i, v in enumerate(l):
    print 'index: {0} val: {1}'.format(i, v)
# index: 0 val: 0
# index: 1 val: 1
# index: 2 val: 2
# index: 3 val: 3
# index: 4 val: 4
# ===

# Set operations
s = set('abracadabra')
t = set('simsalabim')
print s | t  # Union
print s & t  # Intersection
print s - t  # Diff
# set(['a', 'c', 'b', 'd', 'i', 'm', 'l', 's', 'r'])
# set(['a', 'b'])
# set(['c', 'r', 'd'])
# ===

# List operations
l = [str(i) for i in range(10)]
print ''.join(l)
print list(''.join(l))
# 0123456789
# ['0', '1', '2', '3', '4', '5', '6', '7', '8', '9']
# ===

# Lambda Dict
lambda_dict = {
    'lambda1': lambda x, y: x ** y,
    'lambda2': lambda x: x ** 2,
    'lambda3': lambda x: x ** 3
}
print lambda_dict['lambda1'](3, 4), lambda_dict['lambda2'](4)
# 81 16
# ===

# Setter, Getters
class Person(object):
    def __init__(self, FirstName=None, LastName=None):
        self.fn = FirstName
        self.ln = LastName
    @property
    def FirstName(self):
        return self.fn
    @FirstName.setter
    def FirstName(self, value=None):
        self.fn = value
    @property
    def LastName(self):
        return self.ln
    @LastName.setter
    def LastName(self, value=None):
        self.ln = value
p1 = Person('Sponge', 'Bob')
print p1.FirstName, p1.LastName
# Sponge Bob
# ===

# Args, Key-word args
def args_demo(*args, **kwargs):
    print type(args), type(kwargs)
    for i in args:
        print i
    for k, v in kwargs.iteritems():
        print k, v
args_demo(1, 2, 3, a='6', b='7', c='8')
# <type 'tuple'> <type 'dict'>
# 1
# 2
# 3
# a 6
# c 8
# b 7
# ===