00_python_intermediate_workshop.py

## QUIZ TO REVIEW BEGINNER WORKSHOP

a = 5
b = 5.0
c = a/2
d = b/2

'''
What is type(a)?
  int
What is type(b)?
  float
What is c?
  2
What is d?
  2.5
'''

e = [a, b]
f = range(10)

'''
What is type(e)?
  list
What is len(e)?
  2
What is type(f)?
  list
What are the contents of f?
  integers 0 through 9
What is 'range' called?
  a function
How do I get help on 'range'?
  help(range)
'''

g = ['mon','tues','wed','thurs','fri']

'''
How do I slice out 'mon'?
  g[0]
How do I slice out 'mon' through 'wed'?
  g[0:3]
What are two ways to slice out 'fri'?
  g[4] or g[-1]
How do I check the type of 'mon'?
  type(g[0])
'''

g.remove('wed')
sorted(g)
h = sorted(g, reverse=True)

'''
What are the contents of g?
  ['mon','tues','thurs','fri']
What are the contents of h?
  ['tues','thurs','mon','fri']
What is 'remove' called?
  a list method
How do I get help on 'remove'?
  help(g.remove)
What is 'reverse=True' called?
  an optional argument
'''

i = 'Hello'
j = 'friend'
k = i + j
l = i + 3
m = i[0]

'''
What is 'k'?
  'Hellofriend'
What is 'l'?
  undefined (due to error)
What is 'm'?
  'H'
'''



## FOR LOOPS AND BASIC LIST COMPREHENSIONS

# print 1 through 5
nums = range(1, 6)
for num in nums:
    print num

# for loop to create a list of cubes
cubes = []
for num in nums:
    cubes.append(num**3)

# equivalent list comprehension
cubes = [num**3 for num in nums]    # [1, 8, 27, 64, 125]

'''
EXERCISE:
Given that: letters = ['a','b','c']
Write a list comprehension that returns: ['A','B','C']
Hint: 'hello'.upper() returns 'HELLO'

[letter.upper() for letter in letters]

BONUS EXERCISE:
Given that: word = 'abc'
Write a list comprehension that returns: ['A','B','C']

[letter.upper() for letter in word]
'''



## LIST COMPREHENSIONS WITH CONDITIONS

nums = range(1, 6)

# for loop to create a list of cubes of even numbers
cubes_of_even = []
for num in nums:
    if num % 2 == 0:
        cubes_of_even.append(num**3)

# equivalent list comprehension
# syntax: [expression for variable in iterable if condition]
cubes_of_even = [num**3 for num in nums if num % 2 == 0]    # [8, 64]



## DICTIONARIES

# dictionaries are similar to lists:
# - both can contain multiple data types
# - both are iterable
# - both are mutable

# dictionaries are different from lists:
# - dictionaries are unordered
# - dictionary lookup time is constant regardless of dictionary size

# dictionaries are like real dictionaries:
# - dictionaries are made of key-value pairs (word and definition)
# - dictionary keys must be unique (each word is only defined once)
# - you can use the key to look up the value, but not the other way around

# create a dictionary (and open Variable Explorer in Spyder)
family = {'dad':'homer', 'mom':'marge', 'size':6}

# examine a dictionary
family[0]           # throws an error (there is no ordering)
family['dad']       # returns 'homer'
len(family)         # returns 3
family.keys()       # returns list: ['dad', 'mom', 'size']
family.values()     # returns list: ['homer', 'marge', 6]
family.items()      # returns list of tuples:
                    #   [('dad', 'homer'), ('mom', 'marge'), ('size', 6)]

# modify a dictionary
family['cat'] = 'snowball'          # add a new entry
family['cat'] = 'snowball ii'       # edit an existing entry
del family['cat']                   # delete an entry
family['kids'] = ['bart', 'lisa']   # value can be a list

# accessing a list element within a dictionary
family['kids'][0]   # returns 'bart'

'''
EXERCISE:
Given that: d = {'a':10, 'b':20, 'c':[30, 40]}
First, print the value for 'a'
Then, change the value for 'b' to be 25
Then, change the 30 to be 35
Finally, append 45 to the end of the list that contains 35 and 40

d['a']
d['b'] = 25
d['c'][0] = 35
d['c'].append(45)

BONUS EXERCISE:
Write a list comprehension that returns a list of the keys in uppercase

[key.upper() for key in d.keys()]
'''



## APIs

# API Providers: https://apigee.com/providers
# Echo Nest API Console: https://apigee.com/console/echonest
# Echo Nest Developer Center: http://developer.echonest.com/

import requests     # import module (make its functions available)

# use requests to talk to the web
r = requests.get('http://www.google.com')
r.text
type(r.text)

# request data from the Echo Nest API
r = requests.get('http://developer.echonest.com/api/v4/artist/top_hottt?api_key=KBGUPZPJZS9PHWNIN&format=json')
r.text
r.json()        # decode JSON
type(r.json())
top = r.json()

# pretty print for easier readability
import pprint
pprint.pprint(top)

# pull out the artist data
artists = top['response']['artists']    # list of 15 dictionaries

# reformat data into a table structure
artists_data = [artist.values() for artist in artists]  # list of 15 lists
artists_header = artists[0].keys()                      # list of 2 strings



## WORKING WITH PUBLIC DATA

# List of data sources: https://github.com/justmarkham/DAT5/blob/master/other/public_data.md
# FiveThirtyEight: http://fivethirtyeight.com/
# FiveThirtyEight data: https://github.com/fivethirtyeight/data
# NFL ticket prices data: https://github.com/fivethirtyeight/data/tree/master/nfl-ticket-prices

# Question: What is the average ticket price for Ravens' home vs away games?

# open a CSV file from a URL
import csv
r = requests.get('https://raw.githubusercontent.com/fivethirtyeight/data/master/nfl-ticket-prices/2014-average-ticket-price.csv')
data = [row for row in csv.reader(r.iter_lines())]      # list of lists

# open a downloaded CSV file from your working directory
with open('2014-average-ticket-price.csv', 'rU') as f:
    data = [row for row in csv.reader(f)]       # list of lists

# examine the data
type(data)
len(data)
data[0]
data[1]

# save the data we want
data = data[1:97]

# step 1: create a list that only contains events
data[0][0]
data[1][0]
data[2][0]
events = [row[0] for row in data]

# EXERCISE
# step 2: create a list that only contains prices (stored as integers)
prices = [int(row[2]) for row in data]

# step 3: figure out how to locate the away teams
events[0]
events[0].find(' at ')
stop = events[0].find(' at ')
events[0][:stop]

# step 4: use a for loop to make a list of the away teams
away_teams = []
for event in events:
    stop = event.find(' at ')
    away_teams.append(event[:stop])

# EXERCISE
# step 5: use a for loop to make a list of the home teams
home_teams = []
for event in events:
    start = event.find(' at ') + 4
    stop = event.find(' Tickets ')
    home_teams.append(event[start:stop])

# step 6: figure out how to get prices only for Ravens home games
zip(home_teams, prices)     # list of tuples
[pair[1] for pair in zip(home_teams, prices)]   # iterate through tuples and get price
[price for team, price in zip(home_teams, prices)]  # better way to get price
[price for team, price in zip(home_teams, prices) if team == 'Baltimore Ravens']    # add a condition

# step 7: create lists of the Ravens home and away game prices
ravens_home = [price for team, price in zip(home_teams, prices) if team == 'Baltimore Ravens']
ravens_away = [price for team, price in zip(away_teams, prices) if team == 'Baltimore Ravens']

# EXERCISE
# step 8: calculate the average of each list
float(sum(ravens_home)) / len(ravens_home)
float(sum(ravens_away)) / len(ravens_away)