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<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8">
<title>Introduction to Python | Girl Develop It Class 2</title>
<meta name="description" content="This is the official Girl Develop It Core Intro to Python course. The course is meant to be taught in four two-hour sessions. Each of the slides and practice files are customizable according to the needs of a given class or audience.">
<meta name="apple-mobile-web-app-capable" content="yes" />
<meta name="apple-mobile-web-app-status-bar-style" content="black-translucent" />
<link rel="shortcut icon" href="favicon.ico">
<link rel="stylesheet" href="css/reveal.min.css">
<link rel="stylesheet" href="css/theme/gdiaa.css" id="theme">
<link rel="stylesheet" href="lib/css/light.css">
<link rel="stylesheet" href="css/print/pdf.css" media="print">
<script src="lib/js/head.min.js"></script>
<!--[if lt IE 9]>
<script src="lib/js/html5shiv.js"></script>
<![endif]-->
</head>
<body>
<div class="reveal">
<!-- Any section element inside of this container is displayed as a slide -->
<div class="slides">
<!-- Opening slide -->
<section>
<img src="images/gdi_logo_badge.png" class="img--bare" height="450px" />
<div class="box--small">
<h3><span class="green">Intro to Python Class 2</span></h3>
</div>
</section>
<!-- Block 1 30 minutes -->
<section>
<h3>Review</h3>
<ul class="list--xtall box--small">
<li>Arithmetic and variables</li>
<li>Data types</li>
<li>Text editor, command line, and python shell</li>
</ul>
</section>
<section>
<h3>What we will cover today</h3>
<ul span class="box--small list--xtall">
<li class ="fragment">Boolean Expressions and Conditionals</li>
<li class ="fragment">Loops</li>
<li class ="fragment">Functions</li>
</ul>
</section>
<!-- BOOLEANS & CONDITIONALS -->
<section>
<h3>Boolean Expressions</h3>
<p class="box copy--small">We can tell the computer to compare values and return True or False. These are called <strong>Boolean expressions</strong></p>
<ul class="list--tall copy--xsmall">
<li class="fragment">Test for equality by using <code>==</code>. We can't use <code>=</code> because that is used for assignment</li>
<li class="fragment">Test for greater than and less than using <code>></code> and <code><</code></li>
</ul>
<pre class="fragment"><code contenteditable class="python" style="min-height: 50px;">
a = 5
b = 5
print(a == b)
# Combine comparison and assignment
c = a == b
print(c)
print(3 < 5)
</code></pre>
</section>
<section>
<h3>Boolean Expressions continued</h3>
<p class="box--small copy--small">The following chart shows the various Boolean operators</p>
<table class="copy--xsmall" style="width: auto; margin: 0 auto;">
<tr>
<td style="width: 200px;"><code>a == b</code></td>
<td>a is equal to b</td>
</tr>
<tr>
<td style="width: 200px;"><code>a != b</code></td>
<td>a does not equal b</td>
</tr>
<tr>
<td style="width: 200px;"><code>a < b</code></td>
<td>a is less than b</td>
</tr>
<tr>
<td style="width: 200px;"><code>a > b</code></td>
<td>a is greater than b</td>
</tr>
<tr>
<td style="width: 200px;"><code>a <= b</code></td>
<td>a is less than or equal to b</td>
</tr>
<tr>
<td style="width: 200px;"><code>a >= b</code></td>
<td>a is greater than or equal to b</td>
</tr>
</table>
<pre class=""><code contenteditable class="python" style="min-height: 50px;">
a = 3
b = 4
print(a != b)
print(a <= 3)
print(a >= 4)
</code></pre>
<p class="copy--xsmall">Remember: Equals does not equal "equals equals"</p>
</section>
<section>
<h3>Conditionals</h3>
<p class="copy--small box--small">When we want different code to execute dependending on certain criteria, we use a <strong>conditional</strong></p>
<div class="fragment box--small">
<p class="copy--xsmall">We achieve this using <strong>if</strong> statements</p>
<pre><code contenteditable class="small python">
if x == 5:
print('x is equal to 5')
</code></pre></div>
</section>
<section>
<h3>Conditionals</h3>
<div class="fragment box--small">
<p class="copy--xsmall">We often want a different block to execute if the statement is false.<br/>This can be accomplished using <strong>else</strong></p>
<pre><code contenteditable class="small python">
if x == 5:
print('x is equal to 5')
else:
print('x is not equal to 5')
</code></pre>
</div>
</section>
<section>
<h3>Indentation</h3>
<p class="copy--small box--small">In Python, <strong>blocks</strong> <span class="green">begin when text is indented</span> and<br/><span class="red">ends when it returns to the previous indentation</span></p>
<div class="fragment">
<p class="copy--small box--small ">Let's look at the previous example again with a few minor changes and examine the meaning of its indentation</p>
<pre><code contenteditable class=" python">
if x == 5:
print('x is equal to 5')
x_is_5 = True
print('Still in the x == 5 block')
else:
print('x is not equal to 5')
x_is_5 = False
print('Still in the else block of x == 5')
print('Outside of the if or else blocks.')
print('x_is_5:')
print(x_is_5)
</code></pre></div>
</section>
<section>
<h3>Chained conditionals</h3>
<p class="box--small copy--small">Conditionals can also be <strong>chained</strong></p>
<div class="fragment"><p class="box--small copy--small ">Chained conditionals use <code>elif</code> as an additonal check after the preceeding <code>if</code> predicate was False. For example</p>
<pre><code contenteditable class=" python small">
if x > 5:
print('x is greater than 5')
elif x < 5:
print('x is less than 5')
else:
print('x is equal to 5')
</code></pre></div>
</section>
<section>
<h3>Nested conditionals</h3>
<p class="box--small copy--small">Conditionals can also be <strong>nested</strong></p>
<div class="fragment"><p class="box--small copy--small">Nested conditionals occur inside of other conditionals and are indented over once more.</p><p class="box--small copy--small">When the code block is complete, they are unindented</p>
<pre><code contenteditable class="small python">
if x > 5:
print('x is greater than 5')
if x > 10:
print('...it is also greater than 10')
print('Done evaluating the x > 10 block')
print('Done evaluating the x > 5 block')
</code></pre></div>
</section>
<!-- Let's develop it: 10 minutes -->
<section>
<h3>Let's Develop It</h3>
<p class="box--small copy--small">Write a program that uses if statements to determine<br/>what to do given some user input</p>
<p class="box--small copy--small">The code below is an example:</p>
<pre><code contenteditable class=" python">
health = 100
print("A vicious warg is chasing you.")
print("Options:")
print("1 - Hide in the cave.")
print("2 - Climb a tree.")
input_value = input("Enter choice:")
if input_value == '1':
print('You hide in a cave.')
print('The warg finds you and injures your leg with its claws')
health = health - 10
elif input_value == '2':
print('You climb a tree.')
print('The warg eventually looses interest and wanders off')
</code></pre>
</section>
<!-- LOOPS -->
<!-- Block 2 25 minutes -->
<section>
<h3>Iteration</h3>
<p class="box--small copy--small">It is often useful to perform a task and to repeat the process until a certain point is reached.</p>
<p class="box--small copy--small fragment">The repeated execution of a set of statements is called <strong>iteration</strong></p>
<div class="fragment"><p class="box--small copy--small">One way to acheive this, is with the <strong>while</strong> loop.</p>
<pre><code contenteditable class=" small python">
x = 10
while x > 0:
print(x)
x = x - 1
print('Done')
</code></pre></div>
<p class="box--small copy--small fragment">The while statement takes a predicate, and as long as it evaluates to True, the code block beneath it is repeated.</p>
<p class="box--small copy--small fragment">This creates a <strong>loop</strong>. Without the <code>x = x - 1</code> statement, <br/>this would be an <strong>infinite loop</strong></p>
</section>
<section>
<h3>While loops</h3>
<p class="box--small copy--small">Consider the following example that uses iteration to derive a factorial</p>
<p class="box--small copy--xsmall fragment">A factorial of a number is equal to that number * every positive integer less than that number. E.g. The factorial of 4 is 4 * 3 * 2 * 1, which equals 24</p>
<div class="fragment"><pre><code contenteditable class="small python">
input_value = input('Enter a positive integer:') # input('')
n = int(input_value)
result = 1
while n > 1:
result = result * n
n = n - 1
print("The factorial of " + input_value + " is:")
print(result)
</code></pre></div>
<p class="copy--small box--small fragment">This implementation does not work for negative numbers. Why?</p>
</section>
<section>
<h3>For loops</h3>
<p class="copy--small box--small">It is also useful to loop through a collection of elements, visiting each one to do some work, then stopping once all elements are processed.</p>
<p class="copy--small box--small fragment">This can be accomplished with a <strong>for</strong> loop</p>
<div class="fragment"><p class="copy--small box--small ">First, we need a collection. We create a <strong>list</strong> of numbers to loop over. This is called <code>numbers</code> in the following example</p>
<pre><code contenteditable class="small python">
numbers = [1, 3, 8]
for number in numbers:
print("The current number is:")
print(number)
</code></pre></div>
</section>
<section>
<h3>For loops continued</h3>
<p class="copy--small box--small">Let's examine the example carefully</p>
<pre><code contenteditable class="small python">
numbers = [1, 3, 8]
for number in numbers:
print("The current number is:")
print(number)
</code></pre>
<p class="fragment copy--small box--small">The for loop has three parts:</p>
<ul class="list--tall copy--xsmall">
<li class="fragment">The collection to loop over - numbers</li>
<li class="fragment">The name to give each element when the loop begins again - number</li>
<li class="fragment">The block of statements to execute with the element - The two print statements</li>
</ul>
</section>
<!-- Let's Develop It - 10 minutes -->
<section>
<h3>Let's Develop It</h3>
<ul class="list--xtall copy--small box">
<li class="fragment">Write a program that takes numbers from user input and adds thems all together for a final result.</li>
<li class="fragment">This program should stop taking input, display the answer and exit when the user types "quit".</li>
</ul>
</section>
<!-- FUNCTIONS -->
<!-- Block 3 30 minutes -->
<section>
<h3>Functions</h3>
<p class="copy--small box--small">A named section of code that performs a specific task</p>
<p class="copy--small box--small fragment">When one uses a function, one makes a function <strong>call</strong></p>
<div class="fragment"><p class="copy--small box--small ">We have already made a function call<br/>when using the <code>type</code>, <code>int</code>, or <code>float</code> functions</p>
<pre><code contenteditable class=" python small">
a = '3'
print(type(a))
a = float(a)
</code></pre></div>
</section>
<section>
<h3>Function calls</h3>
<pre><code contenteditable class="small python">
a = 3
print(type(a))
</code></pre>
<p class="copy--small box--small">A function can take <strong>arguments</strong></p>
<p class="copy--small box--small">In the example above, the variable <code>a</code> is passed<br/>as an argument to the function <code>type</code></p>
<p class="copy--small box--small fragment">Arguments can also be called <strong>parameters</strong></p>
<div class="fragment "><pre><code contenteditable class="python" style="min-height: 50px;">
# Some more function call examples
int('32')
str(32)
</code></pre></div>
</section>
<section>
<h3>Function definition</h3>
<p class="copy--small box--small">The following example is a <strong>function definition</strong>.<br/>This allows us to create our own functions</p>
<pre><code contenteditable class="small python">
def print_plus_5(x):
print(x + 5)
</code></pre>
<p class="copy--small box--small fragment">The function definition has the following parts</p>
<ul class="copy--xsmall box--small list--tall">
<li class="fragment">The <code>def</code> keyword signifies we are defining a function</li>
<li class="fragment">The name of the function being defined - <code>print_plus_5</code></li>
<li class="fragment">The arguments in parentheses - <code>x</code></li>
<li class="fragment">The function <strong>body</strong>, which is a block of indented code that executes when the function is called. - <code>print x + 5</code></li>
</ul>
</section>
<section>
<h3>Function returns</h3>
<p class="copy--small box--small">A function can also <strong>return</strong> a value</p>
<div class="copy--small box--small fragment"><p>To do this, one uses the <strong>return</strong> keyword</p>
<pre><code contenteditable class=" small python">
def plus_5(x):
return x + 5
y = plus_5(4)
</code></pre></div>
<ul class="list--tall copy--xsmall">
<li class="fragment">This allows us to call a function to obtain a value for later use.<br/>(Not the same as printing the value)</li>
<li class="fragment">In this example, the function call <code>plus_5(4)</code> evaluates to 9, and <code>y</code> is set to this value</li>
<li class="fragment">To determine what a function will return, use the <strong>substitution method</strong>.</li>
<li class="fragment">If return is not used, the function returns <strong>None</strong></li>
</ul>
</section>
<section>
<h3>Functions with no arguments</h3>
<p class="copy--small box--small">A function does not have to take arguments,<br/>as in the following example:
<pre><code contenteditable class="small python">
def newline():
print('')
newline()
# prints an empty line. Nothing is returned
</code></pre>
<p class="copy--xsmall box--small ">This is useful when the function does some work but doesn't need any parameters.<br/>i.e. The function is intended to always do the same thing</p>
</section>
<section>
<h4>Functions with more than one argument</h4>
<p class="copy--small box--small">A function can also take more than one argument separated by commas. For example:</p>
<pre><code contenteditable class="small python">
def find_rectangle_area(width, height):
return width * height
area = find_rectangle_area(3, 4)
# area is set to the value 12
</code></pre>
</section>
<section>
<h3>Import statements</h3>
<p class="copy--small box--small">The <strong>import</strong> statement allows us to use Python code that is defined in one file in a different file</p>
<p class="copy--small box--small fragment">Import statements can be used to import various specialized libraries - such as scikit or nympy - into our code</p>
<p class="copy--small box--small fragment"><strong>def library:</strong> A published collection of useful functions for doing a specific type of coding. There are math, statistics, data science, and graphics libraries, to name a few types.</p>
<p class="copy--small box--small fragment">The <strong>from</strong> keyword allows us to only import parts of a Python file</p>
<div class="fragment "><pre><code contenteditable class="python" style="min-height: 50px;">
from math import sqrt
sqrt(2)
</code></pre></div>
</section>
<!-- Let's develop it: 15 minutes -->
<section>
<h3>Let's Develop It</h3>
<ul class="list--xtall copy--small box--small">
<li>Write a program that uses at least one function to solve a geometry problem</li>
<li>Hint: You might use a loop that obtains user input, does the calculation, then prints the answer. As before, the user should be able to quit by entering "quit"</li>
<li>Hint: You can import your function in the shell and call it with different parameters to test it out</li>
<li>Hint: Download <a href="http://nicklang.com/gdi-intro-python/examples/geometry.py">geometry.py</a> and use it as an example</li>
</ul>
<p class="copy--small box--small">If you'd like to try something different or in addition,<br/>try the next slide...</p>
</section>
<section>
<h3>Let's Develop It</h3>
<ul class="list--tall copy--small box--small">
<li>Write a program that asks the user to guess a number between a given range, such as 1 to 10</li>
<li>The program should give the user hints such as "too high" or "too low". Alternatively, the hints might be "warm" or "cold" depending on how close they are to the number</li>
<li>The computer will need to have a random number for the user to guess:</li>
<pre><code contenteditable class="python" style="min-height: 50px;">
#At the top of the file
from random import randint
# Use this line where you need to have a random number.
# (Hint, this is probably used before the user input loop)
random_number = randint(1, 10)
</code></pre>
</ul>
</section>
<!-- OUTRO -->
<section>
<h3>Questions?</h3>
</section>
<section>
<h3>Homework</h3>
<ul>
<li><p>Write a function that a bar could use to check to see if a customer is of drinking age. <pre>isOfDrinkingAge(age)</pre></p></li>
<li><p>If it is a saturday in spring and it is above 65 degrees, Kermit plants flowers. Write a function to check whether he will plant flowers today. <pre>willKermitPlantFlowers(dayOfWeek, season, currentTemperature)</pre></p></li>
<li><p>Zach knows something is wrong with his basement if the temperature is below 50 or the humidity is above 70%. Write a function that can check whether his basement has a problem. <pre>basementIsOk(temperature, humidity)</pre></p></li>
</ul>
</section>
<section>
<h3>Homework</h3>
<p>Given any list of any sort of mixed types,write a function that prints the type each item in the list. </p>
<p>You can try this list: <pre>[1, 'hello', 12.33, 'data', [1,2]]</pre></p>
<br>
<pre>typeIdentifier(list)</pre>
<pre><code contenteditable class="small python">
#should output something like this:
1 is a <class int>
hello is a <class string>
12.33 is a <class float>
</code></pre>
</section>
<section>
<h3>Homework</h3>
<p>Write a function that asks the user to guess a number between 1 and 100</p>
<ul>
<li class="future"><p>If their guess is within 20, tell them they are 'warm'</p></li>
<li class="future"><p>If their guess is within 10, tell them they are 'hot'</p></li>
<li class="future"><p>If their guess is within 5, tell them they are 'scalding'</p></li>
<li class="future"><p>if their guess is within 50, tell them they are 'cool'</p></li>
<li class="future"><p>otherwise tell them they are 'cold'</p></li>
<li class="future"><p>If they guess the number, congratulate them and ask if they'd like to play again.</p></li>
</ul>
<h6>Optional Extra Challenge: Let them know if they are 'warmer' or 'colder' than their last guess.</h6>
</section>
<section>
<h3>Optional Function Practice</h3>
<pre><code>
# write a function to...
# ...add 10 to any number
# ...divide any number by 100
# ...add any 2 numbers
# ...subtract any 2 numbers
# ...convert celsius to farenheight
# ...convert farenheight to celsius
# ...convert inches to centimeters
# ...convert centimeters to inches
# ...calculate sales tax for any given total amount
# ...calculate the area of a triangle (1/2 base * height)
# ...calculate the volume of a rectangular prism (length * width * height)
</code></pre>
</section>
<section>
<h3>Optional Boolean Practice</h3>
<p>Do this excercise from Learn Python The Hard Way</p>
<i>Make sure to do these problems by hand, not with python! </i>
<h6><a href="https://lpthw.readthedocs.org/en/latest/ex28/">https://lpthw.readthedocs.org/en/latest/ex28/</a></h6>
</section>
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<script>
// Full list of configuration options available here:
// https://github.com/hakimel/reveal.js#configuration
Reveal.initialize({
controls: true,
progress: true,
history: true,
rollingLinks: true,
theme: Reveal.getQueryHash().theme, // available themes are in /css/theme
transition: Reveal.getQueryHash().transition || 'default', // default/cube/page/concave/zoom/linear/none
// Optional libraries used to extend on reveal.js
dependencies: [
{ src: 'lib/js/classList.js', condition: function() { return !document.body.classList; } },
{ src: 'plugin/markdown/showdown.js', condition: function() { return !!document.querySelector( '[data-markdown]' ); } },
{ src: 'plugin/markdown/markdown.js', condition: function() { return !!document.querySelector( '[data-markdown]' ); } },
{ src: 'plugin/highlight/highlight.js', async: true, callback: function() { hljs.initHighlightingOnLoad(); } },
{ src: 'plugin/zoom-js/zoom.js', async: true, condition: function() { return !!document.body.classList; } },
{ src: 'plugin/notes/notes.js', async: true, condition: function() { return !!document.body.classList; } }
]
});
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