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<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml" lang="" xml:lang="">
<head>
<meta charset="utf-8" />
<meta name="generator" content="pandoc" />
<meta
name="viewport"
content="width=device-width, initial-scale=1.0, user-scalable=yes"
/>
<title>README</title>
<style type="text/css">
code {
white-space: pre-wrap;
}
span.smallcaps {
font-variant: small-caps;
}
span.underline {
text-decoration: underline;
}
div.column {
display: inline-block;
vertical-align: top;
width: 50%;
}
</style>
</head>
<body>
<h1 id="python-programming-for-beginners">
Python Programming For Beginners
</h1>
<p>
Python is a very popular coding language. Little people use it for serious
projects, but it is still useful to learn. It was created in 1991 by
<code>Guido van Rossum</code>.<br />
Look at a few uses of python:
</p>
<pre><code>.
├── DOCS
│ ├── _static
│ └── tutorial
├── Readings
├── exploring-python
├── learn-python3-samples
│ ├── advance
│ ├── async
│ ├── basic
│ ├── commonlib
│ ├── context
│ ├── db
│ ├── debug
│ ├── function
│ ├── functional
│ ├── gui
│ │ └── turtle
│ ├── io
│ ├── mail
│ ├── micropython
│ │ ├── hellorobot
│ │ ├── rccar
│ │ ├── smallcar
│ │ └── tank
│ ├── module
│ ├── multitask
│ ├── oop_advance
│ ├── oop_basic
│ ├── regex
│ ├── socket
│ ├── test
│ └── web
│ └── mvc
│ └── templates
├── prac-4-beginners
│ ├── code
│ │ ├── 05-interactive-code
│ │ │ └── m-n-m
│ │ ├── 06-organizing-code-with-functions
│ │ │ └── rocks-game
│ │ ├── 07-data-structures
│ │ │ ├── rocks-game
│ │ │ └── simple_dict
│ │ ├── 08-problem-solving
│ │ │ └── tictactoe
│ │ ├── 09-working-with-files
│ │ │ └── rocks-game
│ │ ├── 10-external-libraries
│ │ │ └── rocks-game
│ │ └── 11-error-handling
│ │ └── rocks-game
│ ├── practices
│ │ ├── ch04_first_lines
│ │ ├── ch05_interactive_code
│ │ ├── ch06-organizing-code-with-functions
│ │ ├── ch07_data_structures
│ │ ├── ch08_problem_solving
│ │ │ └── readme_files
│ │ ├── ch09_working_with_files
│ │ ├── ch10_external_libraries
│ │ └── ch11-error-handling
│ ├── readme_resources
│ └── solutions
│ ├── ch-04-writing-your-first-lines-of-code
│ ├── ch-05-interactive-code
│ ├── ch-06-organizing-code-with-functions
│ ├── ch-07-data-structures
│ ├── ch-08-problem-solving
│ ├── ch-09-working-with-files
│ ├── ch-10-external-libraries
│ └── ch-11-error-handling
├── projecteuler-solutions
├── projects-DS
│ ├── Data-Structures-Notes-master
│ │ ├── BST_and_Heaps
│ │ ├── Doubly_Linked_List
│ │ ├── Interview_Problems
│ │ └── Linked_Lists
│ ├── Data-Structures-and-Algorithms-master
│ │ ├── assets
│ │ └── src
│ │ ├── algorithms
│ │ │ ├── strings
│ │ │ │ └── knuth-morris-pratt
│ │ │ └── tree
│ │ │ ├── breadth-first-search
│ │ │ └── depth-first-search
│ │ ├── analysis-of-algorithms
│ │ │ └── asymptotic-notation
│ │ └── data-structures
│ │ ├── graph
│ │ ├── linked lists
│ │ └── tree
│ │ ├── binary-search-tree
│ │ └── binary-tree
│ ├── Data-Structures-master
│ │ ├── avl_tree
│ │ ├── binary_search_tree
│ │ ├── doubly_linked_list
│ │ ├── heap
│ │ ├── javascript
│ │ │ └── tests
│ │ ├── lru_cache
│ │ ├── python
│ │ │ ├── binary_search_tree
│ │ │ ├── doubly_linked_list
│ │ │ ├── heap
│ │ │ ├── linked_list
│ │ │ └── queue
│ │ └── queue
│ └── data_struct_and_algo-master
└── python-mega-algo
├── arithmetic_analysis
│ └── image_data
├── backtracking
├── bit_manipulation
├── blockchain
├── boolean_algebra
├── cellular_automata
├── ciphers
├── compression
│ └── image_data
├── computer_vision
├── conversions
├── data_structures
│ ├── binary_tree
│ ├── disjoint_set
│ ├── hashing
│ │ └── number_theory
│ ├── heap
│ ├── linked_list
│ ├── queue
│ ├── stacks
│ └── trie
├── digital_image_processing
│ ├── dithering
│ ├── edge_detection
│ ├── filters
│ ├── histogram_equalization
│ │ ├── image_data
│ │ └── output_data
│ ├── image_data
│ ├── resize
│ └── rotation
├── divide_and_conquer
├── dynamic_programming
├── electronics
├── file_transfer
│ └── tests
├── fractals
├── fuzzy_logic
├── genetic_algorithm
├── geodesy
├── graphics
├── graphs
│ └── tests
├── hashes
├── knapsack
│ └── tests
├── linear_algebra
│ └── src
├── machine_learning
│ ├── forecasting
│ └── lstm
├── maths
│ ├── images
│ └── series
├── matrix
│ └── tests
├── networking_flow
├── neural_network
├── other
├── physics
├── project_euler
│ ├── problem_001
│ ├── problem_002
│ ├── problem_003
│ ├── problem_004
│ ├── problem_005
│ ├── problem_006
│ ├── problem_007
│ ├── problem_008
│ ├── problem_009
│ ├── problem_010
│ ├── problem_011
│ ├── problem_012
│ ├── problem_013
│ ├── problem_014
│ ├── problem_015
│ ├── problem_016
│ ├── problem_017
│ ├── problem_018
│ ├── problem_019
│ ├── problem_020
│ ├── problem_021
│ ├── problem_022
│ ├── problem_023
│ ├── problem_024
│ ├── problem_025
│ ├── problem_026
│ ├── problem_027
│ ├── problem_028
│ ├── problem_029
│ ├── problem_030
│ ├── problem_031
│ ├── problem_032
│ ├── problem_033
│ ├── problem_034
│ ├── problem_035
│ ├── problem_036
│ ├── problem_037
│ ├── problem_038
│ ├── problem_039
│ ├── problem_040
│ ├── problem_041
│ ├── problem_042
│ ├── problem_043
│ ├── problem_044
│ ├── problem_045
│ ├── problem_046
│ ├── problem_047
│ ├── problem_048
│ ├── problem_049
│ ├── problem_050
│ ├── problem_051
│ ├── problem_052
│ ├── problem_053
│ ├── problem_054
│ ├── problem_055
│ ├── problem_056
│ ├── problem_057
│ ├── problem_058
│ ├── problem_059
│ ├── problem_062
│ ├── problem_063
│ ├── problem_064
│ ├── problem_065
│ ├── problem_067
│ ├── problem_069
│ ├── problem_070
│ ├── problem_071
│ ├── problem_072
│ ├── problem_074
│ ├── problem_075
│ ├── problem_076
│ ├── problem_077
│ ├── problem_080
│ ├── problem_081
│ ├── problem_085
│ ├── problem_086
│ ├── problem_087
│ ├── problem_089
│ ├── problem_091
│ ├── problem_097
│ ├── problem_099
│ ├── problem_101
│ ├── problem_102
│ ├── problem_107
│ ├── problem_109
│ ├── problem_112
│ ├── problem_113
│ ├── problem_119
│ ├── problem_120
│ ├── problem_121
│ ├── problem_123
│ ├── problem_125
│ ├── problem_129
│ ├── problem_135
│ ├── problem_173
│ ├── problem_174
│ ├── problem_180
│ ├── problem_188
│ ├── problem_191
│ ├── problem_203
│ ├── problem_206
│ ├── problem_207
│ ├── problem_234
│ ├── problem_301
│ └── problem_551
├── quantum
├── scheduling
├── scripts
├── searches
├── sorts
├── strings
└── web_programming
286 directories</code></pre>
<p>
Python syntax was made for readability, and easy editing. For example, the
python language uses a <code>:</code> and indented code, while javascript
and others generally use <code>{}</code> and indented code.
</p>
<p>
Lets create a
<a href="https://repl.it/languages/python3">python 3</a> repl, and call it
<em>Hello World</em>. Now you have a blank file called <em>main.py</em>.
Now let us write our first line of code:
</p>
<p><em>helloworld.py</em></p>
<pre><code>print('Hello world!')</code></pre>
<blockquote>
<p>
Brian Kernighan actually wrote the first “Hello, World!” program as part
of the documentation for the BCPL programming language developed by
Martin Richards.
</p>
</blockquote>
<p>
Now, press the run button, which <sub>obviously</sub> runs the code. If
you are not using replit, this will not work. You should research how to
run a file with your text editor.
</p>
<p>
If you look to your left at the console where hello world was just
printed, you can see a <code>></code>, <code>>>></code>, or
<code>$</code> depending on what you are using. After the prompt, try
typing a line of code.
</p>
<pre><code>Python 3.6.1 (default, Jun 21 2017, 18:48:35)
[GCC 4.9.2] on linux
Type "help", "copyright", "credits" or "license" for more information.
> print('Testing command line')
Testing command line
> print('Are you sure this works?')
Are you sure this works?
></code></pre>
<p>
The command line allows you to execute single lines of code at a time. It
is often used when trying out a new function or method in the language.
</p>
<p>
Another cool thing that you can generally do with all languages, are
comments. In python, a comment starts with a <code>#</code>. The computer
ignores all text starting after the <code>#</code>.
</p>
<p><em>shortcom.py</em></p>
<pre><code># Write some comments!</code></pre>
<p>
If you have a huge comment, do <strong>not</strong> comment all the 350
lines, just put <code>'''</code> before it, and <code>'''</code> at the
end. Technically, this is not a comment but a string, but the computer
still ignores it, so we will use it.
</p>
<p><em>longcom.py</em></p>
<pre><code>'''
Dear PYer,
I am confused about how you said you could use triple quotes to make
SUPER
LONG
COMMENTS
!
I am wondering if this is true,
and if so,
I am wondering if this is correct.
Could you help me with this?
Thanks,
Random guy who used your tutorial.
'''
print('Testing')</code></pre>
<p>
Unlike many other languages, there is no <code>var</code>,
<code>let</code>, or <code>const</code> to declare a variable in python.
You simply go <code>name = 'value'</code>.
</p>
<p><em>vars1.py</em></p>
<pre><code>x = 5
y = 7
z = x*y # 35
print(z) # => 35</code></pre>
<p>
Remember, there is a difference between integers and strings.
<em>Remember: String = <code>""</code>.</em> To convert between these two,
you can put an int in a <code>str()</code> function, and a string in a
<code>int()</code> function. There is also a less used one, called a
float. Mainly, these are integers with decimals. Change them using the
<code>float()</code> command.
</p>
<p><em>vars2.py</em></p>
<pre><code>x = 5
x = str(x)
b = '5'
b = int(b)
print('x = ', x, '; b = ', str(b), ';') # => x = 5; b = 5;</code></pre>
<p>
Instead of using the <code>,</code> in the print function, you can put a
<code>+</code> to combine the variables and string.
</p>
<p>There are many operators in python:</p>
<ul>
<li><code>+</code></li>
<li><code>-</code></li>
<li><code>/</code></li>
<li>
<code>*</code><br />
These operators are the same in most languages, and allow for addition,
subtraction, division, and multiplicaiton.<br />
Now, we can look at a few more complicated ones:
</li>
<li><code>%</code></li>
<li><code>//</code></li>
<li><code>**</code></li>
<li><code>+=</code></li>
<li><code>-=</code></li>
<li><code>/=</code></li>
<li>
<code>*=</code><br />
Research these if you want to find out more…
</li>
</ul>
<p><em>simpleops.py</em></p>
<pre><code>x = 4
a = x + 1
a = x - 1
a = x * 2
a = x / 2</code></pre>
<p>
You should already know everything shown above, as it is similar to other
languages. If you continue down, you will see more complicated ones.
</p>
<p><em>complexop.py</em></p>
<pre><code>a += 1
a -= 1
a *= 2
a /= 2</code></pre>
<p>
The ones above are to edit the current value of the variable.<br />
Sorry to JS users, as there is no <code>i++;</code> or anything.
</p>
<blockquote>
<p>
Fun Fact:<br />
The python language was named after Monty Python.
</p>
</blockquote>
<p>
If you really want to know about the others, view
<a href="https://www.tutorialspoint.com/python/python_basic_operators.htm"
>Py Operators</a
>
</p>
<p>
Like the title?<br />
Anyways, a <code>'</code> and a <code>"</code> both indicate a string, but
<strong>do not combine them!</strong>
</p>
<p><em>quotes.py</em></p>
<pre><code>x = 'hello' # Good
x = "hello" # Good
x = "hello' # ERRORRR!!!</code></pre>
<p><em>slicing.py</em></p>
<h3 id="string-slicing">String Slicing</h3>
<p>
You can look at only certain parts of the string by slicing it, using
<code>[num:num]</code>.<br />
The first number stands for how far in you go from the front, and the
second stands for how far in you go from the back.
</p>
<pre><code>x = 'Hello everybody!'
x[1] # 'e'
x[-1] # '!'
x[5] # ' '
x[1:] # 'ello everybody!'
x[:-1] # 'Hello everybod'
x[2:-3] # 'llo everyb'</code></pre>
<h3 id="methods-and-functions">Methods and Functions</h3>
<p>Here is a list of functions/methods we will go over:</p>
<ul>
<li><code>.strip()</code></li>
<li><code>len()</code></li>
<li><code>.lower()</code></li>
<li><code>.upper()</code></li>
<li><code>.replace()</code></li>
<li><code>.split()</code></li>
</ul>
<p>
I will make you try these out yourself. See if you can figure out how they
work.
</p>
<p><em>strings.py</em></p>
<pre><code>x = " Testing, testing, testing, testing "
print(x.strip())
print(len(x))
print(x.lower())
print(x.upper())
print(x.replace('test', 'runn'))
print(x.split(','))</code></pre>
<p>Good luck, see you when you come back!</p>
<p>
Input is a function that gathers input entered from the user in the
command line. It takes one optional parameter, which is the users prompt.
</p>
<p><em>inp.py</em></p>
<pre><code>print('Type something: ')
x = input()
print('Here is what you said: ', x)</code></pre>
<p>
If you wanted to make it smaller, and look neater to the user, you could
do…
</p>
<p><em>inp2.py</em></p>
<pre><code>print('Here is what you said: ', input('Type something: '))</code></pre>
<p>
Running:<br />
<em>inp.py</em>
</p>
<pre><code>Type something:
Hello World
Here is what you said: Hello World</code></pre>
<p><em>inp2.py</em></p>
<pre><code>Type something: Hello World
Here is what you said: Hello World</code></pre>
<p>
Python has created a lot of functions that are located in other .py files.
You need to import these <strong>modules</strong> to gain access to the,,
You may wonder why python did this. The purpose of separate modules is to
make python faster. Instead of storing millions and millions of functions,
, it only needs a few basic ones. To import a module, you must write
<code>input <modulename></code>. Do not add the .py extension to the
file name. In this example , we will be using a python created module
named random.
</p>
<p><em>module.py</em></p>
<pre><code>import random</code></pre>
<p>
Now, I have access to all functions in the random.py file. To access a
specific function in the module, you would do
<code><module>.<function></code>. For example:
</p>
<p><em>module2.py</em></p>
<pre><code>import random
print(random.randint(3,5)) # Prints a random number between 3 and 5</code></pre>
<blockquote>
<p>
Pro Tip:<br />
Do <code>from random import randint</code> to not have to do
<code>random.randint()</code>, just <code>randint()</code><br />
To import all functions from a module, you could do
<code>from random import *</code>
</p>
</blockquote>
<p>
Loops allow you to repeat code over and over again. This is useful if you
want to print Hi with a delay of one second 100 times.
</p>
<h4 id="for-loop"><code>for</code> Loop</h4>
<p>
The for loop goes through a list of variables, making a seperate variable
equal one of the list every time.<br />
Let’s say we wanted to create the example above.
</p>
<p><em>loop.py</em></p>
<pre><code>from time import sleep
for i in range(100):
print('Hello')
sleep(.3)</code></pre>
<p>
This will print Hello with a .3 second delay 100 times. This is just one
way to use it, but it is usually used like this:
</p>
<p><em>loop2.py</em></p>
<pre><code>import time
for number in range(100):
print(number)
time.sleep(.1)</code></pre>
<p>
<a
href="https://storage.googleapis.com/replit/images/1539649280875_37d22e6d49e8e8fbc453631def345387.pn"
></a>
</p>
<h4 id="while-loop"><code>while</code> Loop</h4>
<p>
The while loop runs the code while something stays true. You would put
<code>while <expression></code>. Every time the loop runs, it
evaluates if the expression is True. It it is, it runs the code, if not it
continues outside of the loop. For example:
</p>
<p><em>while.py</em></p>
<pre><code>while True: # Runs forever
print('Hello World!')</code></pre>
<p>Or you could do:</p>
<p><em>while2.py</em></p>
<pre><code>import random
position = '<placeholder>'
while position != 1: # will run at least once
position = random.randint(1, 10)
print(position)</code></pre>
<p>
The if statement allows you to check if something is True. If so, it runs
the code, if not, it continues on. It is kind of like a while loop, but it
executes <strong>only once</strong>. An if statement is written:
</p>
<p><em>if.py</em></p>
<pre><code>import random
num = random.randint(1, 10)
if num == 3:
print('num is 3. Hooray!!!')
if num > 5:
print('Num is greater than 5')
if num == 12:
print('Num is 12, which means that there is a problem with the python language, see if you can figure it out. Extra credit if you can figure it out!')</code></pre>
<p>
Now, you may think that it would be better if you could make it print only
one message. Not as many that are True. You can do that with an
<code>elif</code> statement:
</p>
<p><em>elif.py</em></p>
<pre><code>import random
num = random.randint(1, 10)
if num == 3:
print('Num is three, this is the only msg you will see.')
elif num > 2:
print('Num is not three, but is greater than 1')</code></pre>
<p>
Now, you may wonder how to run code if none work. Well, there is a simple
statement called <code>else:</code>
</p>
<p><em>else.py</em></p>
<pre><code>import random
num = random.randint(1, 10)
if num == 3:
print('Num is three, this is the only msg you will see.')
elif num > 2:
print('Num is not three, but is greater than 1')
else:
print('No category')</code></pre>
<p>
So far, you have only seen how to use functions other people have made.
Let use the example that you want to print the a random number between 1
and 9, and print different text every time.<br />
It is quite tiring to type:
</p>
<p>Characters: 389</p>
<p><em>nofunc.py</em></p>
<pre><code>import random
print(random.randint(1, 9))
print('Wow that was interesting.')
print(random.randint(1, 9))
print('Look at the number above ^')
print(random.randint(1, 9))
print('All of these have been interesting numbers.')
print(random.randint(1, 9))
print("these random.randint's are getting annoying to type")
print(random.randint(1, 9))
print('Hi')
print(random.randint(1, 9))
print('j')</code></pre>
<p>Now with functions, you can seriously lower the amount of characters:</p>
<p>Characters: 254</p>
<p><em>functions.py</em></p>
<pre><code>import random
def r(t):
print(random.randint(1, 9))
print(t)
r('Wow that was interesting.')
r('Look at the number above ^')
r('All of these have been interesting numbers.')
r("these random.randint's are getting annoying to type")
r('Hi')
r('j')</code></pre>
<p>
<a
href="https://storage.googleapis.com/replit/images/1539906570970_88961cdd6d7c76c15c92cd79307dbb06.pn"
></a>
</p>
<h2 id="chapter-01---getting-ready-with-python">
Chapter 01 - Getting Ready with Python
</h2>
<h3 id="installing-python-3-and-launching-python-shell">
Installing Python 3, And Launching Python Shell
</h3>
<p>This video should help you get up and running with Python 3</p>
<ul>
<li>
<a href="https://www.youtube.com/watch?v=Ji1WW4Suaww"
>Installing Python 3 and Launch Python Shell</a
>
</li>
</ul>
<p>
Installing Python is really a cakewalk. Search for “Python download” on
www.google.com. Download the installable and install it.
</p>
<p>A quick word of caution on Windows</p>
<ul>
<li>
Make sure that you have the check-box “Add Python 3.6 to PATH”, checked.
</li>
</ul>
<p>Once you have installed Python, you can launch the Python Shell.</p>
<ul>
<li>Windows - Launch cmd prompt by typing in ‘cmd’ command.</li>
<li>Mac or Linux - Launch up terminal.</li>
</ul>
<p>Command to launch Python 3 is different in Mac.</p>
<ul>
<li>In Mac, type in <code>python3</code></li>
<li>
In other operating systems, including windows, type <code>python</code>
</li>
</ul>
<p>You can type code in python shell and code as well!</p>
<p>You can use <code>print(5*4)</code>, and it shows <code>20</code>.</p>
<p>
You can execute the code, and the shell would immediately give you output.
</p>
<p>Using the the Python Shell is an awesome way to learn Python.</p>
<h2 id="chapter-02---introduction-to-python-programming">
Chapter 02 - Introduction To Python Programming
</h2>
<p>
Most programmers find programming a lot of fun, and besides, it also gets
their work done.
</p>
<p>
Programming mainly involves <em>problem solving</em>, where one makes use
of a computer to solve a real world problem.
</p>
<p>
During our journey here, we will approach programming in a very different
way. We will not only introduce you to the Python language, but also help
you pick up essential problem solving skills.
</p>
<p>
As a programmer, you need to be able to look at a problem, and identify
the important programming concepts relevant to solving it. Finally, you
need to be able to use the language features and syntax, to express your
solution on the computer. While all this looks complex, we want to make it
easy for you. Together, we will tackle a variety of programming
challenges, using these same steps. We will start with simple challenges
(such as a Multiplication Table), and gradually increase the difficulty
level over the duration of this book.
</p>
<p>
Learning to program is a lot like learning to ride a bicycle. The first
few steps are the most challenging ones.
</p>
<p>
Once you get over these initial steps, your experience will become more
and more enjoyable.
</p>
<p>
Are you ready for your first programming challenge? Let’s get going now!
We wish you all the best.
</p>
<h4 id="summary">Summary</h4>
<p>In this step, we:</p>
<ul>
<li>Were introduced to the concept of problem solving</li>
<li>Understood how good programmers approach problem solving</li>
</ul>
<h3 id="step-01-our-first-programming-challenge">
Step 01: Our First Programming Challenge
</h3>
<p>
Our first <em>programming challenge</em> aims to do, what every kid does
in math class: read out a multiplication table. We now want to give this
task to the computer. Here is the statement of our problem:
</p>
<h4 id="the-print-multiplication-table-challenge-pmt-challenge">
The <strong>Print Multiplication Table Challenge (PMT-Challenge)</strong>
</h4>
<ol type="1">
<li>
Compute the multiplication table for <code>5</code>, with entries from
<code>1</code> to <code>10</code>.
</li>
<li>Display this table.</li>
</ol>
<p>The display needs to be:</p>
<p>
<strong><em>5 * 1 = 5</em></strong>
</p>
<p>
<strong><em>5 * 2 = 10</em></strong>
</p>
<p>
<strong><em>5 * 3 = 15</em></strong>
</p>
<p>
<strong><em>5 * 4 = 20</em></strong>
</p>
<p>
<strong><em>5 * 5 = 25</em></strong>
</p>
<p>
<strong><em>5 * 6 = 30</em></strong>
</p>
<p>
<strong><em>5 * 7 = 35</em></strong>
</p>
<p>
<strong><em>5 * 8 = 40</em></strong>
</p>
<p>
<strong><em>5 * 9 = 45</em></strong>
</p>
<p>
<strong><em>5 * 10 = 50</em></strong>
</p>
<p>
This is the challenge. For convenience, let’s give it a label, say
<em>PMT-Challenge</em>. What would be the important concepts we need to
learn, to solve this challenge? The following list of concepts would be a
good starting point:
</p>
<ul>
<li><strong>Statements</strong></li>
<li><strong>Expressions</strong></li>
<li><strong>Variables</strong></li>
<li><strong>Literals</strong></li>
<li><strong>Conditionals</strong></li>
<li><strong>Loops</strong></li>
<li><strong>Methods</strong></li>
</ul>
<p>
In the rest of this chapter, we will introduce these concepts to you,
one-by-one. We will also show you how learning each concept, takes us
closer to a solution to <em>PMT-Challenge</em>.
</p>
<h4 id="summary-1">Summary</h4>
<p>In this step, we:</p>
<ul>
<li>Stated our first programming challenge</li>
<li>
Identified what programming concepts we need to learn, to solve this
challenge
</li>
</ul>
<h3 id="step-02-breaking-down-pmt-challenge">
Step 02: Breaking Down <em>PMT-Challenge</em>
</h3>
<p>
Typically when we do programming, we have problems. Solving the problem
typically need a step-by -step approach. Common sense tells us that to
solve a complex problem, we break it into smaller parts, and solve each
part one by one. Here is how any good programmer worth her salt, would
solve a problem:
</p>
<ul>
<li>Simplify the problem, by breaking it into sub-problems</li>
<li>
Solve the sub-problems in stages (in some order), using the language
</li>
<li>Combine these solutions to get a final solution</li>
</ul>
<p>
The <em>PMT-Challenge</em> is no different! Now how do we break it down,
and where do we really start? Once again, your common sense will reveal a
solution. As a first step, we could get the computer to calculate say,
<code>5 * 3</code>. The second thing we can do, is to try and print the
calculated value, in a manner similar to <code>5 * 3 = 15</code>. Then, we
could repeat what we just did, to print out all the entries of the
<code>5</code> multiplication table. Let’s put it down a little more
formally:
</p>
<p>Here is how our draft steps look like</p>
<ul>
<li>Calculate <code>5 * 3</code> and print result as <code>15</code></li>
<li>
Print <code>5 * 3 = 15</code> (<code>15</code> is result of previous
calculation)
</li>
<li>
Do this ten times, once for each table entry (going from
<code>1</code> to <code>10</code>)
</li>
</ul>
<p>Let’s start with that kind of a game plan, and see where it takes us.</p>
<h4 id="summary-2">Summary</h4>
<p>In this step, we:</p>
<ul>
<li>
Learned that breaking down a problem into sub-problems is a great help
</li>
<li>Found a way to break down the <em>PMT-Challenge</em> problem</li>
</ul>
<h3 id="step-03-introducing-operators-and-expressions">
Step 03: Introducing Operators And Expressions
</h3>
<p>
Let’s focus on solving the first sub-problem of <em>PMT-Challenge</em>,
the numeric computation. We want the computer to calculate
<code>5 * 5</code> for example, and print <code>25</code> for us. How do
we get it to do that? That’s what we would be looking at in this step.
</p>
<h4 id="snippet-01-introducing-operators">
Snippet-01: Introducing Operators
</h4>
<p>
Launch up Python shell. We want to calculate <code>5 * 5</code>. How do we
do that?
</p>
<p>Using our knowledge of school math, let’s try <code>5 X 5</code>.</p>
<pre><code> >>> 5 X 5
File "< stdin >", line 1
5 X 5
^
SyntaxError: invalid syntax</code></pre>
<p>
The Python Shell hits back at us, saying “<em>invalid syntax</em>”. This
is how Python complains, when it doesn’t fully understand the code you
type in. Here, it says our code has a “<strong>SyntaxError</strong>”.
</p>
<p>
The reason why it complains, is because ‘<code>X</code>’ is not a valid
<strong>operator</strong> in Python.
</p>
<p>
The way you can do multiplication is by using the ‘<code>*</code>’
<em>operator</em> .
</p>
<p>
“<em>5 into 5</em>” is achieved by the code <code>5 * 5</code>, and you
can see the result <code>25</code> being printed. Similarly,
<code>5 * 6</code> gives us <code>30</code>.
</p>
<pre><code> >>> 5 * 6
30</code></pre>
<p>There are a wide range of other operators in Python:</p>
<ul>
<li><code>5 + 6</code> gives a result of <code>11</code>.</li>
<li>
<p><code>5 - 6</code> leads to <code>-1</code>.</p>
<pre><code>>>> 5 + 6
11
>>> 5 - 6
-1</code></pre>
</li>
</ul>
<p>
<code>10 / 2</code>, gives an output of <code>5.0</code> . There is one
interesting operator, <code>**</code>. Let’s try <code>10 ** 3</code>. We
ran this code, and the result we get is <code>1000</code>. Yes you guessed
right, the operator performs “to the power of”. “<code>10</code> to the
power of <code>3</code>” is <code>10 * 10 * 10</code>, or
<code>1000</code>.
</p>
<pre><code> >>> 10 / 2
5.0
>>> 10 ** 3
1000</code></pre>
<p>
Another interesting operator is <code>%</code>, called “<em>modulo</em>”,
which computes the remainder on integer division. If we do
<code>10 % 3</code>, what is the remainder when <code>10</code> is divided
by <code>3</code>? <code>3 * 3</code> is <code>9</code>, and
<code>10 - 9</code> is <code>1</code>, which is what
<code>%</code> returns in this case.
</p>
<p>Let’s look at some terminology:</p>
<ul>
<li>
Whatever pieces of code we gave Python shell to run, are called
<strong>expressions</strong>. So, <code>5 * 5</code>,
<code>5 * 6</code> and <code>5 - 6</code> are all <em>expressions</em>.
An expression is composed of <em>operators</em> and
<strong>operands</strong>.
</li>