Chicago Python Workshop/Projects

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Welcome to the Saturday afternoon projects section of the Chicago Python Workshop! After lunch, we'll break out into groups to practice Python through using the Twitter API to write the basic parts of a Twitter client. We'll also work through a WordPlay exercise to practice manipulating and matching strings.

Setup[edit]

See the Friday setup instructions.

Twitter[edit]

Twitter.png

Twitter

Use the Twitter API to write the basic parts of a Twitter client. See what your friends are tweeting, get trending topics, search tweets, and more.

Twitter goals[edit]

  • practice for loops
  • practice using functions
  • practice implementing functions
  • see what it's like to use an API
  • have fun collecting data from Twitter

Concept review[edit]

Indentation reminder[edit]

In Python, indentation matters. Everything is indented by a multiple of some number of spaces, often 4.

In if statements, you indent everything you want to be run if the if conditional is True. For example:

>>> James = 35
>>> Alice = 30
>>> if James > Alice:
...     print "James is older than Alice."
...
James is older than Alice.
>>>

Because James really is older than Alice, the if conditional is True, so Python does execute the code indented under the if line. In this case we print "James is older than Alice."

>>> James = 35
>>> Alice = 30
>>> if James < Alice:
...     print "James is younger than Alice."
...
>>>

Because James is not older than Alice, the if conditional is False, so Python does not execute the code indented under the if line.

In for loops, you indent everything you want to be run each loop For example:

>>> names = ["Jessica", "Adam", "Liz"]
>>> for name in names:
...     print "Hello " + name
...
Hello Jessica
Hello Adam
Hello Liz

The print line is indented 4 spaces under the for. That's how Python knows to execute the print line for every name in names.

Functions[edit]

Let's review what we know about functions:

  • They do some useful bit of work.
  • They let us re-use code without having to type it out each time.
  • They take input and possibly produce output (we say they return a value). You can assign a variable to this output.
  • You define a function using the def keyword.
  • You call a function by using its name followed by its arguments in parenthesis.

Here's an example:

>>> def add(x, y):
...     return x + y
...
>>> add(1, 2)
3
>>> add(-1, 1)
0
>>> add(.5, .75)
1.25

pass[edit]

pass is a keyword that just means "do nothing". It most often shows up as a place-holder for code that doesn't exist yet. For example:

>>> def testFunction():
...     pass
...
>>>

Imports[edit]

Imports look like this:

>>> import random
>>> import time

In the above example, random and time are both Python modules. Modules are Python files outside of the current Python file that contain Python code, like functions and variables. You can use code from modules by first importing the module. Here's an example from the random module:

>>> import random
>>> random.randint(0, 10)
7
>>> random.randint(0, 10)
6
>>> random.randint(0, 10)
1
>>> random.randint(0, 10)
3
>>> random.randint(0, 10)
4
>>> random.randint(0, 10)
9

randint is a function in the random module. It takes a lower bound as the first argument and an upper bound as the second argument and returns a random integer between those bounds.

Python Twitter library functions we will use[edit]

A library provides a collection of functions for you, and defines a contract for using those functions. Here are the functions in the python-twitter library that will be useful for the project:

api.GetSearch(searchString)

Given a string to search for, this function will return a list of tweets matching that search string.

api.GetUserTimeline(username)

Given a username, this function will return a list of tweets belonging to that username.

Python Twitter Project Instructions[edit]

Here are the Twitter Project Instructions.

Wordplay[edit]

Crossword.png

Download the Wordplay project[edit]

We've written some skeleton code for the Wordplay project already. Download this code so you're ready to start working with it tomorrow:

  1. Right click the following file, click "Save Target as..." or "Save link as...", and save it to your Desktop directory:
  2. Windows:
    1. Find Wordplay.zip on your Desktop and double-click on it to "unzip" it. That will create a folder called Wordplay containing several files.
  3. Mac OSX
    1. Find Wordplay.zip on your Desktop and double-click on it. This will create a directory for Wordplay, containing the source code for the dependency.
  4. Linux
    1. Find Wordplay.tar.gz on your Desktop and double-click on it to "extract" it. That will create a folder called Wordplay containing several files.

Test the Wordplay code[edit]

Start a command prompt and navigate to the Desktop\Wordplay directory where the Wordplay code lives. For example, if the Wordplay project is at C:\Users\jesstess\Desktop\Wordplay,

cd C:\Users\jesstess\Desktop\Wordplay

will change you into that directory, and

dir

will show you the source code files in that directory. One of the files is "words1.py", which has a ".py" extension indicating that it is a Python script. Type:

python words1.py

at the command prompt to execute the words1.py Python script. You should see a column of English words printed to the screen. If you don't, let a staff member know.

Success![edit]

You've completed setup for the Wordplay project.

Wordplay goals[edit]

  • practice for loops
  • practice using lists
  • practice manipulating strings
  • get experience with regular expressions
  • have fun cheating at crosswords and Words with Friends

Concept review[edit]

Indentation reminder[edit]

In Python, indentation matters. Everything is indented by a multiple of some number of spaces, often 4.

In if statements, you indent everything you want to be run if the if conditional is True. For example:

>>> James = 35
>>> Alice = 30
>>> if James > Alice:
...     print "James is older than Alice."
...
James is older than Alice.
>>>

Because James really is older than Alice, the if conditional is True, so Python does execute the code indented under the if line. In this case we print "James is older than Alice."

>>> James = 35
>>> Alice = 30
>>> if James < Alice:
...     print "James is younger than Alice."
...
>>>

Because James is not older than Alice, the if conditional is False, so Python does not execute the code indented under the if line.

In for loops, you indent everything you want to be run each loop For example:

>>> names = ["Jessica", "Adam", "Liz"]
>>> for name in names:
...     print "Hello", name
...
Hello Jessica
Hello Adam
Hello Liz

The print line is indented 4 spaces under the for. That's how Python knows to execute the print line for every name in names.

range[edit]

>>> range(5)
[0, 1, 2, 3, 4]
>>> for i in range(5):
...     print "Hi" * i
...

Hi
HiHi
HiHiHi
HiHiHiHi

if statements inside for loops[edit]

>>> for i in range(80):
...     if i % 9 == 0:
...         print i, "is divisible by 9."
...
0 is divisible by 9.
9 is divisible by 9.
18 is divisible by 9.
27 is divisible by 9.
36 is divisible by 9.
45 is divisible by 9.
54 is divisible by 9.
63 is divisible by 9.
72 is divisible by 9.

for loops inside for loops[edit]

>>> letters = ["a", "b", "c"]
>>> numbers = [1, 2, 3]
>>> for letter in letters:
...     for number in numbers:
...         print letter * number
...
a
aa
aaa
b
bb
bbb
c
cc
ccc
>>> for number in numbers:
...     for letter in letters:
...         print number * letter
...
a
b
c
aa
bb
cc
aaa
bbb
ccc

Imports[edit]

Imports look like this:

>>> import random
>>> import time

In the above example, random and time are both Python modules. Modules are Python files outside of the current Python file that contain Python code, like functions and variables. You can use code from modules by first importing the module. Here's an example from the random module:

>>> import random
>>> random.randint(0, 10)
7
>>> random.randint(0, 10)
6
>>> random.randint(0, 10)
1
>>> random.randint(0, 10)
3
>>> random.randint(0, 10)
4
>>> random.randint(0, 10)
9

randint is a function in the random module. It takes a lower bound as the first argument and an upper bound as the second argument and returns a random integer between those bounds.

New Wordplay material summary[edit]

in keyword[edit]

in is a keyword checking for containment. You can use it in a couple of ways:

>>> "a" in "apple"
True
>>> "z" in "apple"
False
>>> dogs = ["pug", "boxer", "dalmation"]
>>> "tiger" in dogs
False
>>> "pug" in dogs
True

Reversing lists[edit]

Here's a quick way to reverse a list.

>>> fruits = ["apples", "bananas", "cherries"]
>>> fruits[::-1]
['cherries', 'bananas', 'apples']

Let's break down why this works:

First, remember that we can get individual elements from lists:

>>> fruits[0]
'apples'

We can also slice lists:

>>> fruits[0:2]
['apples', 'bananas']
>>> fruits[:2]
['apples', 'bananas']
>>> fruits[1:]
['bananas', 'cherries']

We can also make a copy of the list by taking a slice from the beginning to the end of the list:

>>> my_fruits = fruits[:]
['apples', 'bananas', 'cherries']

There's an extended slicing syntax that let's you say what direction you want to slice in. By default it is forward, but you can supply a -1 to say backwards:

>>> fruits[::-1]
['cherries', 'bananas', 'apples']

Regular expressions[edit]

  • ^ is an anchor that means "beginning"
  • $ is an anchor that means "end"
  • . means a single wildcard character
  • .* means any number (including zero) of wildcard characters

Examples:

  • rstu will match anything that contains "rstu", for example "understudy".
  • ^aa will match anything that starts with "aa", for example "aardvark".
  • a.b.c will match anything containing "a", then any single character, then "b", then any single character, then "c", for example "iambic".
  • ss.*ss will match anything containing "ss", then anything, then "ss", for example "messiness".
  • ^c.d.e$ will match anything that starts with "c", then any single character, then d, then any single character, then ends with an "e", for example "cadre".

Python Wordplay Project Instructions[edit]

Here are the Wordplay Project Instructions.