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<div class="presentation">
<div class="slide" id="slide0">
</div>
<div class="slide" id="history-of-python">
<h1>History of Python</h1>
<dl class="docutils">
<dt>Developed by Guido von Rossum in 1989 at CWI</dt>
<dd><ul class="first last simple">
<li>CWI is a research institution funded by the Dutch government</li>
<li>Guido needed something that was faster for development than C, less tied to Unix then Perl and bash.</li>
</ul>
</dd>
</dl>
</div>
<div class="slide" id="who-uses-python">
<h1>Who uses Python?</h1>
<ul class="simple">
<li>Google (Guido works there)</li>
<li>DemonWare (Call of Duty servers)</li>
<li>CCP Games (EVE Online)</li>
<li>CRC (web development, scientific libraries)</li>
<li>Dropbox</li>
<li>Canonical (creators of Ubuntu)</li>
</ul>
</div>
<div class="slide" id="what-is-python">
<h1>What is Python?</h1>
<ul class="simple">
<li>An object-oriented, dynamically typed, interpreted, general purpose programming language</li>
<li>Open source, BSD-like license</li>
<li>Supported on lots of platforms</li>
</ul>
</div>
<div class="slide" id="general-purpose">
<h1>General Purpose</h1>
<dl class="docutils">
<dt>Used for lots of different programming tasks</dt>
<dd><ul class="first last simple">
<li>Automatic repetitive administrative tasks</li>
<li>Scientific calculations (libraries like SciPy and NumPy)</li>
<li>Web development (Django, Pyramid, Flask, Google App Engine, so on and so forth)</li>
</ul>
</dd>
</dl>
</div>
<div class="slide" id="interpreted">
<h1>Interpreted</h1>
<p>Python code is translated to machine code at runtime, not in a prior compilation step.</p>
<dl class="docutils">
<dt>Several interpreters</dt>
<dd><ul class="first last simple">
<li>Standard CPython</li>
<li>PyPy project</li>
<li>Stackless</li>
</ul>
</dd>
</dl>
</div>
<div class="slide" id="dynamically-typed">
<h1>Dynamically Typed</h1>
<ul class="simple">
<li>Languages like Chapel, C, Java require variables to have their type declared on creation</li>
<li>Python does not; a variable can hold any kind of value.</li>
</ul>
<p>Examples:</p>
<pre class="literal-block">
a = "a string"
a = 1
</pre>
</div>
<div class="slide" id="id1">
<h1>Dynamically Typed</h1>
<ul>
<li><p class="first">Variable's <em>properties</em> are important, not it's data type.</p>
</li>
<li><dl class="first docutils">
<dt>Also known as "duck typing".</dt>
<dd><ul class="first last simple">
<li>"If it walks like a duck and quacks like a duck, it's a duck".</li>
</ul>
</dd>
</dl>
</li>
</ul>
</div>
<div class="slide" id="object-oriented">
<h1>Object-Oriented</h1>
<ul class="simple">
<li>Data and the functions related to it is associated through objects</li>
<li>Objects are instances classes.</li>
<li>More on this later.</li>
</ul>
</div>
<div class="slide" id="data-types">
<h1>Data Types</h1>
<ul>
<li><dl class="first docutils">
<dt>Several generic, basic data types:</dt>
<dd><ul class="first last simple">
<li>Integers</li>
<li>Floats</li>
<li>Strings</li>
<li>Booleans</li>
<li>Objects</li>
</ul>
</dd>
</dl>
</li>
</ul>
</div>
<div class="slide" id="collections">
<h1>Collections</h1>
<ul class="simple">
<li>Lists</li>
<li>Dictionaries</li>
<li>Tuples</li>
</ul>
</div>
<div class="slide" id="running-python">
<h1>Running Python</h1>
<p>The interactive interpreter
From your shell prompt, type:</p>
<pre class="literal-block">
$ python
</pre>
<p>Get something like:</p>
<pre class="literal-block">
Python 2.6.1 (r261:67515, Jun 24 2010, 21:47:49)
[GCC 4.2.1 (Apple Inc. build 5646)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>>
</pre>
</div>
<div class="slide" id="the-interactive-interpreter">
<h1>The Interactive Interpreter</h1>
<p>You can type in valid Python expressions in order to test things out:</p>
<pre class="literal-block">
>>> name = "Guido von Rossum"
>>> year = 1990
>>> print name
Guido von Rossum
>>> print year
1990
>>> 1 + 2
3
>>>
</pre>
</div>
<div class="slide" id="string-interpolation">
<h1>String Interpolation</h1>
<p>We assigned some variables and printed some things.</p>
<p>But it can be more interesting.:</p>
<pre class="literal-block">
>>> print "%s made Python." % name
Guido von Rossum made Python.
</pre>
<p>We can use <em>string interpolation</em> to substitute a variable's value into a string.</p>
</div>
<div class="slide" id="excercise-1">
<h1>Excercise 1</h1>
<p>Make the interactive interpreter return the following string:</p>
<blockquote>
"Hello, <em>[your name here]</em>"</blockquote>
</div>
<div class="slide" id="lists">
<h1>Lists</h1>
<p>Lists are like arrays in Chapel.</p>
<p>Similar declaration, too.:</p>
<pre class="literal-block">
numbers = [1, 2, 3]
</pre>
<p>However, unlike statically typed languages, lists can contain any data type.:</p>
<pre class="literal-block">
my_list = ["Python", 2, 8.0, []]
</pre>
<p>Can also add to them and remove elements.</p>
<p>Order matters.</p>
</div>
<div class="slide" id="tuples">
<h1>Tuples</h1>
<p>Like lists, however, you cannot modify them once created.</p>
<p>Example:</p>
<pre class="literal-block">
coordinates = (3, 4)
</pre>
<p>Tuple with a single element:</p>
<pre class="literal-block">
weird_tuple = ("Guido",)
</pre>
<p>Parentheses are also used for grouping, hence the comma.</p>
</div>
<div class="slide" id="iteration-loops">
<h1>Iteration/Loops</h1>
<p>Used to repeat a single instruction multiple times.</p>
<p>Really useful for operating on collections.</p>
<p>For and while loops.</p>
</div>
<div class="slide" id="for-loops">
<h1>For Loops</h1>
<p>Structure::</p>
<pre class="literal-block">
for variable_name in collection_name:
# do things
</pre>
<p>Note: everything inside the loop is <em>indented</em>!</p>
</div>
<div class="slide" id="quick-note-on-indentation">
<h1>Quick Note on Indentation</h1>
<ul>
<li><p class="first">Python uses indentation to control code structure.</p>
</li>
<li><p class="first">Other languages use braces ( { and } )</p>
</li>
<li><dl class="first docutils">
<dt>Python only cares that your indentation is consistent</dt>
<dd><ul class="first last simple">
<li>Don't mix tabs and spaces</li>
<li>Most often, people use 4 spaces as the indent-level</li>
</ul>
</dd>
</dl>
</li>
</ul>
</div>
<div class="slide" id="back-to-loops">
<h1>Back to Loops</h1>
<p>Example:</p>
<pre class="literal-block">
>>>> author_names = ["Matz", "Guido", "Larry"]
>>> for name in author_names:
... print name
...
Matz
Guido
Larry
</pre>
</div>
<div class="slide" id="exercise-2">
<h1>Exercise 2</h1>
<p>Print your name 20 times.</p>
<p>Hint: Instead of a list or tuple in the <tt class="docutils literal">collection_name</tt> spot, use <tt class="docutils literal">range(0,20)</tt>.</p>
<p>It's kind of like Chapel's range syntax.</p>
</div>
<div class="slide" id="dictionaries">
<h1>Dictionaries</h1>
<ul class="simple">
<li>A collection of <em>key, value pairs</em>.</li>
<li>Associates a <em>key</em> (which can be a number, string, object, whatever), with a <em>value</em>.</li>
<li>Unordered - when accessing a dictionary, items may not come out in the same order they were added.</li>
</ul>
</div>
<div class="slide" id="dictionary-examples">
<h1>Dictionary Examples</h1>
<p>A basic dictionary:</p>
<pre class="literal-block">
>>> {"shoe_size": 12}
</pre>
<p>Multiple items:</p>
<pre class="literal-block">
>>> {"name": "Frank", "height": 6.0}
</pre>
</div>
<div class="slide" id="accessing-a-dictionary">
<h1>Accessing a Dictionary</h1>
<p>First, let's create a dictionary, with a variable:</p>
<pre class="literal-block">
>>> my_dictionary = {"name": "Fred"}
</pre>
<p>Next, we can retrieve the value associated with the <tt class="docutils literal">name</tt> key:</p>
<pre class="literal-block">
>>> my_dictionary["name"]
'Fred'
</pre>
</div>
<div class="slide" id="looping-with-dictionaries">
<h1>Looping with Dictionaries</h1>
<p>Using just the dictionary in the for statement we saw before only works on the dictionary keys.</p>
<p>To access both, we use the <tt class="docutils literal">items</tt> method on the dictionary. (Those will be explained soon):</p>
<pre class="literal-block">
>>>> language_authors = {"Matz": "Ruby", "Guido": "Python",
... "Larry": "Perl"}
>>> for key, value in language_authors.items():
... print "%s wrote %s" % (key, value)
...
Larry wrote Perl
Matz wrote Ruby
Guido wrote Python
</pre>
</div>
<div class="slide" id="things-to-note">
<h1>Things to note</h1>
<p>Instead of one loop variable, we had two.</p>
<p>When we used multiple values in string interpolation, we used a tuple.</p>
<p>The loop didn't print the values in the same order we put them in.</p>
</div>
<div class="slide" id="functions">
<h1>Functions</h1>
<p>Functions break up programs into logical pieces</p>
<p>Very much like procedures in Chapel</p>
<p>A stepping stone to objects.</p>
<p>An example:</p>
<pre class="literal-block">
def adder(val1, val2):
return val1 + val2
</pre>
<p>Functions have <em>names</em> (<tt class="docutils literal">adder</tt>), take <em>arguments</em> (<tt class="docutils literal">val1, val2</tt>) and can <em>return</em> a result.</p>
</div>
<div class="slide" id="arguments">
<h1>Arguments</h1>
<p>We use the previous function like this:</p>
<pre class="literal-block">
>>> adder(2, 3)
5
</pre>
<p>The value <tt class="docutils literal">2</tt> is put into <tt class="docutils literal">val1</tt>, and <tt class="docutils literal">3</tt> into <tt class="docutils literal">val2</tt>.
<tt class="docutils literal">val1</tt> and <tt class="docutils literal">val2</tt> are confined to the <tt class="docutils literal">adder</tt> function:</p>
<pre class="literal-block">
>>>> val1
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
NameError: name 'val1' is not defined
</pre>
<p>This is called <em>scope</em>.</p>
</div>
<div class="slide" id="null-arguments">
<h1>Null arguments</h1>
<p>You can also have functions without any arguments:</p>
<pre class="literal-block">
def print_hello():
print "Hello"
</pre>
<dl class="docutils">
<dt>2 things here:</dt>
<dd><ul class="first last simple">
<li>The parentheses are simply empty.</li>
<li>Notice we didn't return anything; in Python we don't have to.</li>
</ul>
</dd>
</dl>
</div>
<div class="slide" id="interlude-using-python-files">
<h1>Interlude - Using Python Files</h1>
<p>You can use <tt class="docutils literal">gedit</tt> to edit Python files, saving them with the extension <tt class="docutils literal">.py</tt>.</p>
<p>Then, you can run the files with this command:</p>
<pre class="literal-block">
$ python my_file.py
</pre>
</div>
<div class="slide" id="control-flow">
<h1>Control Flow</h1>
<p>Python uses <tt class="docutils literal">if</tt> statements that look similar to Chapel's, but without the braces.</p>
<p>Basic structure:</p>
<pre class="literal-block">
if something:
transform(1,2)
elif something_else:
transform(2,3)
else:
transform(3,4)
</pre>
</div>
<div class="slide" id="check-if-a-value-is-in-a-collection">
<h1>Check if a value is in a collection</h1>
<p>Using a conditional with the <tt class="docutils literal">in</tt> keyword to see if a particular value is contained in a collection:</p>
<pre class="literal-block">
>>> if "Yes" in ["Yes", "No"]:
... print "Yep, it's there."
...
Yep, it's there.
>>> if "Joe" not in ["Sam", "Frank"]:
... print "Joe's not there."
...
Joe's not there.
</pre>
</div>
<div class="slide" id="exercise-3">
<h1>Exercise 3</h1>
<p>Create a function that returns "weekday" if a day's name is a weekday, "weekend" if it's not.</p>
<dl class="docutils">
<dt>Hints:</dt>
<dd><ul class="first last">
<li><p class="first">Just worry about lower case values</p>
</li>
<li><p class="first">Getting user input:</p>
<pre class="literal-block">
>>>> day = raw_input("Input a day's name >> ")
Input a day's name >> Monday
>>> day
'Monday'
</pre>
</li>
</ul>
</dd>
</dl>
<p>Bonus: If the word given isn't a valid calendar day, return "neither"</p>
</div>
<div class="slide" id="object-oriented-programming">
<h1>Object Oriented Programming</h1>
<ul>
<li><p class="first">Object-oriented programming tries to model program strutures after things in the real world.</p>
</li>
<li><dl class="first docutils">
<dt>Objects have:</dt>
<dd><ul class="first last simple">
<li><em>properties</em> that describe them (the bike is red)</li>
<li><em>methods</em> that make them do things (the man runs).</li>
</ul>
</dd>
</dl>
</li>
<li><p class="first">Together, these are called <em>members</em></p>
</li>
<li><p class="first">Benefit: information is contained only in the area it's necessary ("information hiding")</p>
</li>
<li><dl class="first docutils">
<dt>Objects are:</dt>
<dd><ul class="first last simple">
<li>defined by writing a <em>class</em></li>
<li>created by <em>instantiating</em> a class</li>
</ul>
</dd>
</dl>
</li>
</ul>
</div>
<div class="slide" id="classes">
<h1>Classes</h1>
<p>Think of classes like a <em>template</em> for objects; it describes how they will work</p>
<p>But, the objects contain specific information</p>
</div>
<div class="slide" id="example">
<h1>Example</h1>
<ul>
<li><dl class="first docutils">
<dt>The Car Class describes cars:</dt>
<dd><ul class="first last simple">
<li>They have four wheels, color(s), number of seats, make, model, VIN,
can accelerate, deccelerate, turn, etc.</li>
</ul>
</dd>
</dl>
</li>
<li><p class="first">The <em>actual</em> color, number of seats, VIN, make, model corresponds to the specific car.</p>
</li>
<li><p class="first">The <em>verbs</em> (the things they can do) are shared amongst all of them.</p>
</li>
</ul>
</div>
<div class="slide" id="id2">
<h1>Example</h1>
<ul class="simple">
<li>The Dog Class describes dogs: They have a color, four legs, eye color, breed(s), can bark, run, etc.</li>
<li>Fido is a black labrador</li>
<li>Butch is a white bulldog</li>
</ul>
</div>
<div class="slide" id="making-the-connection">
<h1>Making the connection</h1>
<ul class="simple">
<li>Properties are <em>variables</em> - these can be any valid data type, including other objects!</li>
<li>Methods are <em>functions</em> - these <em>do</em> things, and are common to all instances of the object</li>
<li>Objects hold <em>state</em> in their properties, which is then changed by methods.</li>
</ul>
</div>
<div class="slide" id="defining-a-class">
<h1>Defining a class</h1>
<p>Example:</p>
<pre class="literal-block">
>>>> class Dog(object):
... def __init__(self, name=None, breed=None):
... self.name = name
... self.breed = breed
... def bark(self):
... print '%s says, "Woof!"' % self.name
... def bark(self, target):
... print "%s barks at %s!" % (self.name, target.name)
...
>>> fido = Dog(name="Fido", breed="Black Lab")
>>> fido.bark()
Fido says, "Woof!"
</pre>
</div>
<div class="slide" id="things-of-note">
<h1>Things of note</h1>
<ul>
<li><dl class="first docutils">
<dt>All classes:</dt>
<dd><ul class="first last">
<li><dl class="first docutils">
<dt>should be defined as <tt class="docutils literal">class ClassName(object)</tt></dt>
<dd><ul class="first last simple">
<li><tt class="docutils literal">ClassName</tt> inherits from <tt class="docutils literal">object</tt>.</li>
</ul>
</dd>
</dl>
</li>
<li><dl class="first docutils">
<dt>define an initializer function, <tt class="docutils literal">__init__</tt></dt>
<dd><ul class="first last simple">
<li>This is a "magic method" that Python uses.</li>
<li>Similar to C++/Java constructors - it sets up initial state</li>
</ul>
</dd>
</dl>
</li>
</ul>
</dd>
</dl>
</li>
</ul>
</div>
<div class="slide" id="id3">
<h1>Things of note</h1>
<ul class="simple">
<li>All methods take <tt class="docutils literal">self</tt> as the first argument</li>
<li>Different methods can have the same name, if they take different number of arguments.</li>
<li><tt class="docutils literal">self</tt> is <em>not</em> passed in when you call the function; Python's interpreter uses it, not the programmer.</li>
<li>Variables attached to <tt class="docutils literal">self</tt> can be accessed in any other method in that class.</li>
<li>I snuck in named arguments there; done for clarity.</li>
</ul>
</div>
<div class="slide" id="more-theory-inheritance">
<h1>More Theory: Inheritance</h1>
<ul>
<li><dl class="first docutils">
<dt>Classes can <em>inherit</em> from others.</dt>
<dd><ul class="first last simple">
<li>This means that the <em>subclass</em> shares properties and methods with it's <em>superclass</em></li>
<li>Also referred to as <em>child</em> and <em>parent</em> classes</li>
</ul>
</dd>
</dl>
</li>
</ul>
<p>Examples:</p>
<ul class="simple">
<li>A parent class could be Vehicle, and subclasses would be Car, Motorcycle, Truck, Tractor, etc</li>
<li>Another parent class could be Animal, subclasses being Cat, Dog, Giraffe, Elephant, etc</li>
</ul>
</div>
<div class="slide" id="hierarchies">
<h1>Hierarchies</h1>
<p>You can also have hierarchies:</p>
<ul>
<li><dl class="first docutils">
<dt>Animal</dt>
<dd><ul class="first last">
<li><dl class="first docutils">
<dt>Mammal</dt>
<dd><ul class="first last simple">
<li>Dog</li>
<li>Cat</li>
</ul>
</dd>
</dl>
</li>
<li><dl class="first docutils">
<dt>Bird</dt>
<dd><ul class="first last simple">
<li>Eagle</li>
</ul>
</dd>
</dl>
</li>
</ul>
</dd>
</dl>
</li>
</ul>
</div>
<div class="slide" id="inheritance-in-python">
<h1>Inheritance in Python</h1>
<p><tt class="docutils literal">class ChildClass(ParentClass)</tt></p>
<p>except for the parent class, which looks like</p>
<p><tt class="docutils literal">class ParentClass(object)</tt></p>
<p>Why?</p>
<ul class="simple">
<li><tt class="docutils literal">object</tt> is a type, just like <tt class="docutils literal">int</tt> or <tt class="docutils literal">str</tt>. Helps Python allocate memory correctly.</li>
</ul>
</div>
<div class="slide" id="exercise-4">
<h1>Exercise 4</h1>
<p>Create a Python class that represents a mathematical vector (<a class="reference external" href="http://en.wikipedia.org/wiki/Euclidean_vector">http://en.wikipedia.org/wiki/Euclidean_vector</a>)</p>
<p>Vectors are pairs of x, y coordinates. We want the following members:</p>
<ul class="simple">
<li>x coordinate</li>
<li>y coordinate</li>
<li>adding 2 vectors (x1 added to x2, y1 added to y2)</li>
<li>subtracting 2 vectors (x1 minus x2, y1 minus x2)</li>
<li>a __repr__(self) method that returns the coordinates as the string "(x, y)"</li>
</ul>
</div>
<div class="slide" id="exercise-4-hints">
<h1>Exercise 4 Hints</h1>
<p>Should look something like this:</p>
<pre class="literal-block">
v1 = Vector(1,3)
v2 = Vector(8,9)
v1.add(v2)
print v1
(9, 12)
</pre>
<p>Bonus: Write a method that multiplies both x and y by a single number (scalar multiplication)</p>
</div>
<div class="slide" id="modules-and-packages">
<h1>Modules and Packages</h1>
<ul class="simple">
<li>Python code is organized into modules and packages.</li>
<li><em>Modules</em> are individual Python files.</li>
<li><em>Packages</em> are directories that contain Python modules</li>
<li>Modules and packages are used to distribute re-usable code.</li>
</ul>
</div>
<div class="slide" id="standard-library">
<h1>Standard Library</h1>
<ul>
<li><p class="first">Python has a philosophy of "batteries included".</p>
</li>
<li><p class="first">LOTS of modules/packages bundled with Python.</p>
</li>
<li><p class="first">Examples:</p>
<pre class="literal-block">
os
zlib
datetime
hashlib
threading
socket
unittest
</pre>
</li>
<li><p class="first">External packages, too, like SciPy, NumPy, PyCUDA, Django, SQLAlchemy, Pygments, etc</p>
</li>
</ul>
</div>
<div class="slide" id="using-packages-and-modules">
<h1>Using packages and modules</h1>
<p>2 forms:</p>
<ul class="simple">
<li><tt class="docutils literal">import os</tt></li>
<li><tt class="docutils literal">from os import path</tt></li>
</ul>
</div>
<div class="slide" id="getting-help-with-packages-modules">
<h1>Getting help with packages/modules</h1>
<ul class="simple">
<li>Use the <tt class="docutils literal">dir</tt> function to inspect an object's members, packages and modules included</li>
<li>Use the <tt class="docutils literal">help</tt> function to get help for an object.</li>
</ul>
<p>Example (output shortened):</p>
<pre class="literal-block">
>>>> import os
>>> dir(os)
[.... 'walk', 'write']
>>> help(os.walk)
Help on function walk in module os: