DAT8/code/00_python_intermediate_workshop.py at master · justmarkham/DAT8 · GitHub

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'''

Python Intermediate Workshop

'''

LISTS

'''

# creating

a = [1, 2, 3, 4, 5] # create lists using brackets

# slicing

a[0] # returns 1 (Python is zero indexed)

a[1:3] # returns [2, 3] (inclusive of first index but exclusive of second)

a[-1] # returns 5 (last element)

# appending

a[5] = 6 # error because you can't assign outside the existing range

a.append(6) # list method that appends 6 to the end

a = a + [0] # use plus sign to combine lists

# checking length

len(a) # returns 7

# checking type

type(a) # returns list

type(a[0]) # returns int

# sorting

sorted(a) # sorts the list

sorted(a, reverse=True) # reverse=True is an 'optional argument'

sorted(a, True) # error because optional arguments must be named

'''

STRINGS

'''

# creating

a = 'hello' # can use single or double quotes

# slicing

a[0] # returns 'h' (works like list slicing)

a[1:3] # returns 'el'

a[-1] # returns 'o'

# concatenating

a + ' there' # use plus sign to combine strings

5 + ' there' # error because they are different types

str(5) + ' there' # cast 5 to a string in order for this to work

# uppercasing

a[0] = 'H' # error because strings are immutable (can't overwrite characters)

a.upper() # string method (this method doesn't exist for lists)

# checking length

len(a) # returns 5 (number of characters)

'''

EXERCISE:

1. Create a list of the first names of your family members.

2. Print the name of the last person in the list.

3. Print the length of the name of the first person in the list.

4. Change one of the names from their real name to their nickname.

5. Append a new person to the list.

6. Change the name of the new person to lowercase using the string method 'lower'.

7. Sort the list in reverse alphabetical order.

Bonus: Sort the list by the length of the names (shortest to longest).

'''

names = ['Wesley', 'Larry', 'Wan'] # list of names

names[-1] # last element

len(names[0]) # length of first string

names[0] = 'Wes' # overwrite existing element

names.append('Gabriel') # append new element

names[-1] = names[-1].lower() # change last string to be lowercase

sorted(names, reverse=True) # sort the list in reverse order

sorted(names, key=len) # sort the list by length

'''

FOR LOOPS AND LIST COMPREHENSIONS

'''

# for loop to print 1 through 5

nums = range(1, 6) # create a list of 1 through 5

for num in nums: # num 'becomes' each list element for one loop

print num

# for loop to print 1, 3, 5

other = [1, 3, 5] # create a different list

for x in other: # name 'x' does not matter, not defined in advance

print x # this loop only executes 3 times (not 5)

# for loop to create a list of 2, 4, 6, 8, 10

doubled = [] # create empty list to store results

for num in nums: # loop through nums (will execute 5 times)

doubled.append(num*2) # append the double of the current value of num

# equivalent list comprehension

doubled = [num*2 for num in nums] # expression (num*2) goes first, brackets

# indicate we are storing results in a list

'''

EXERCISE 1:

Given that: letters = ['a', 'b', 'c']

Write a list comprehension that returns: ['A', 'B', 'C']

EXERCISE 2 (BONUS):

Given that: word = 'abc'

Write a list comprehension that returns: ['A', 'B', 'C']

EXERCISE 3 (BONUS):

Given that: fruits = ['Apple', 'Banana', 'Cherry']

Write a list comprehension that returns: ['A', 'B', 'C']

'''

letters = ['a', 'b', 'c']

[letter.upper() for letter in letters] # iterate through a list of strings,

# and each string has an 'upper' method

word = 'abc'

[letter.upper() for letter in word] # iterate through each character

fruits = ['Apple', 'Banana', 'Cherry']

[fruit[0] for fruit in fruits] # slice the first character from each string

'''

DICTIONARIES

'''

# dictionaries are made of key-value pairs (like a real dictionary)

family = {'dad':'Homer', 'mom':'Marge', 'size':2}

# check the length

len(family) # returns 3 (number of key-value pairs)

# use the key to look up a value (fast operation regardless of dictionary size)

family['dad'] # returns 'Homer'

# can't use a value to look up a key

family['Homer'] # error

# dictionaries are unordered

family[0] # error

# add a new entry

family['cat'] = 'snowball'

# keys must be unique, so this edits an existing entry

family['cat'] = 'snowball ii'

# delete an entry

del family['cat']

# keys can be strings or numbers or tuples, values can be any type

family['kids'] = ['bart', 'lisa'] # value can be a list

# accessing a list element within a dictionary

family['kids'][0] # returns 'bart'

# useful methods

family.keys() # returns list: ['dad', 'kids', 'mom', 'size']

family.values() # returns list: ['Homer', ['bart', 'lisa'], 'Marge', 2]

family.items() # returns list of tuples:

# [('dad', 'Homer'), ('kids', ['bart', 'lisa']), ('mom', 'Marge'), ('size', 2)]

'''

EXERCISE:

1. Print the name of the mom.

2. Change the size to 5.

3. Add 'Maggie' to the list of kids.

4. Fix 'bart' and 'lisa' so that the first letter is capitalized.

Bonus: Do this last step using a list comprehension.

'''

family['mom'] # returns 'Marge'

family['size'] = 5 # replaces existing value for 'size'

family['kids'].append('Maggie') # access a list, then append 'Maggie' to it

family['kids'][0] = 'Bart' # capitalize names by overwriting them

family['kids'][1] = 'Lisa'

# or, capitalize using a list comprehension and the 'capitalize' string method

family['kids'] = [kid.capitalize() for kid in family['kids']]

# or, slice the string, uppercase the first letter, and concatenate with other letters

family['kids'] = [kid[0].upper() + kid[1:] for kid in family['kids']]

'''

REQUESTS

'''

# import module (make its functions available)

import requests

# use requests to talk to the web

r = requests.get('http://www.google.com')

type(r) # special 'response' object

r.text # HTML of web page stored as string

type(r.text) # string is encoded as unicode

r.text[0] # string can be sliced like any string

'''

APIs

What is an API?

- Application Programming Interface

- Structured way to expose specific functionality and data access to users

- Web APIs usually follow the "REST" standard

How to interact with a REST API:

- Make a "request" to a specific URL (an "endpoint"), and get the data back in a "response"

- Most relevant request method for us is GET (other methods: POST, PUT, DELETE)

- Response is often JSON format

- Web console is sometimes available (allows you to explore an API)

API Providers: https://apigee.com/providers

Echo Nest API Console: https://apigee.com/console/echonest

API key: http://bit.ly/myechonest

'''

# 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 # looks like a dictionary

type(r.text) # actually stored as a string

r.json() # decodes JSON

type(r.json()) # JSON can be represented as a dictionary

top = r.json() # store that dictionary

# store the artist data

artists = top['response']['artists'] # list of 15 dictionaries

# create a list of artist names only

names = [artist['name'] for artist in artists] # can iterate through list to access dictionaries

DAT8/code/00_python_intermediate_workshop.py at master · justmarkham/DAT8 · GitHub

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