#!/usr/bin/env python

from math import sqrt

animals = ['cat', 'dog', 'monkey']

for animal in animals:

print animal

# for List

nums = [0, 1, 2, 3, 4]

square = []

for num in nums:

square.append( num ** 2 )

print square

## learn this type of assignment in the [ ]

even_squares = [ num ** 2 for num in nums if num % 2 == 0 ]

print even_squares

## dictionary is similar to the Map(Key:Value)

d = {'cat':'cute', 'dog':'furry'}

print d['cat']

print 'cat' in d # check whether there is a key in the dictionary

d['fish'] = 'wet'

print d['fish']

print d.get('monkey', 'N/A') # get an element with a default N/A

print d.get('fish', 'N/A')

del d['fish']

print d.get('fish', 'N/A')

## some examples about dictionary and for loop

for animal in d:

value = d[animal]

print animal + ": " + value

## use iteritems to get the key and value NOTE!!!!

d = {'person':2, 'cat':4, 'spider':8}

for animal, leg in d.iteritems():

print "%s has %d legs" % (animal, leg)

nums = [1, 2, 3, 4, 5]

square_pair = {x: x ** 2 for x in nums if x % 2 == 0}

print square_pair

### Sets

animals = {'cat', 'dog'}

print 'cat' in animals

print 'fog' in animals

animals.add('fish')

print 'fish' in animals

print len(animals)

animals.add('cat')

print animals

animals.remove('cat')

print animals

## list the elements of Sets

animals = {'cat', 'dog', 'fish'}

for idx, animal in enumerate(animals):

print "$%d: %s" % (idx+1, animal)

### construct the Sets

nums = {int(sqrt(x)) for x in range(30)} # Sets will avoid the repeated numbers

print nums

### Tuple: value cannot be changed

d = {(x, x+1): x for x in range(10)}

print d

t = (5, 6)

print type(t)

print d[t]

print d[(1, 2)]