Boston Python Workshop 4/Twitter handout: Difference between revisions
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There's nothing like the reilef of finding what you're looking for. |
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===Twitter goals=== |
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* practice for loops |
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* practice using functions |
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* practice implementing functions |
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* see what it's like to use an API |
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* have fun collecting data from Twitter |
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===Concept review=== |
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====Indentation reminder==== |
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In Python, indentation matters. Everything is indented by a multiple |
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of some number of spaces, often 4. |
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In <code>if</code> statements, you indent everything you want to be run if the if |
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conditional is <code>True</code>. For example: |
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<pre> |
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>>> James = 35 |
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>>> Alice = 30 |
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>>> if James > Alice: |
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... print "James is older than Alice." |
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... |
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James is older than Alice. |
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>>></pre> |
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Because James really is older than Alice, the <code>if</code> conditional is <code>True</code>, |
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so Python does execute the code indented under the if line. In this |
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case we print "James is older than Alice." |
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<pre> |
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>>> James = 35 |
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>>> Alice = 30 |
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>>> if James < Alice: |
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... print "James is younger than Alice." |
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... |
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>>></pre> |
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Because James is not older than Alice, the <code>if</code> conditional is <code>False</code>, so |
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Python does not execute the code indented under the if line. |
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In for loops, you indent everything you want to be run each loop For |
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example: |
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<pre> |
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>>> names = ["Jessica", "Adam", "Liz"] |
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>>> for name in names: |
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... print "Hello", name |
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... |
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Hello Jessica |
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Hello Adam |
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Hello Liz</pre> |
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The <code>print</code> line is indented 4 spaces under the <code>for</code>. That's how |
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Python knows to execute the print line for every name in names. |
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====Functions==== |
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Let's review what we know about functions: |
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* They do some useful bit of work. |
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* They let us re-use code without having to type it out each time. |
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* They take input and possibly produce output (we say they return a value). You can assign a variable to this output. |
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* You define a function using the def keyword. |
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* You call a function by using its name followed by its arguments in parenthesis. |
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Here's an example: |
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<pre> |
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>>> def add(x, y): |
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... return x + y |
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... |
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>>> add(1, 2) |
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3 |
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>>> add(-1, 1) |
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0 |
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>>> add(.5, .75) |
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1.25</pre> |
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====pass==== |
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<code>pass</code> is a keyword that just means "do nothing". It most often shows up |
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as a place-holder for code that doesn't exist yet. For example: |
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<pre> |
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>>> def testFunction(): |
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... pass |
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... |
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>>></pre> |
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====Imports==== |
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Imports look like this: |
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<pre> |
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>>> import random |
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>>> import time</pre> |
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In the above example, <code>random</code> and <code>time</code> are both Python modules. Modules |
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are Python files outside of the current Python file that contain |
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Python code, like functions and variables. You can use code from |
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modules by first importing the module. Here's an example from the |
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<code>random</code> module: |
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<pre> |
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>>> import random |
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>>> random.randint(0, 10) |
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7 |
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>>> random.randint(0, 10) |
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6 |
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>>> random.randint(0, 10) |
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1 |
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>>> random.randint(0, 10) |
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3 |
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>>> random.randint(0, 10) |
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4 |
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>>> random.randint(0, 10) |
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9</pre> |
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<code>randint</code> is a function in the <code>random</code> module. It takes a lower bound as |
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the first argument and an upper bound as the second argument and |
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returns a random integer between those bounds. |
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Latest revision as of 20:14, 15 January 2012
There's nothing like the reilef of finding what you're looking for.