Boston Python Workshop 6/Twitter handout

From OpenHatch wiki

Twitter goals

  • 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

Indentation reminder

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

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

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

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

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.


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