Python Programming - II. The Basics

Engr. Ranel O. Padon
PYTHON PROGRAMMING
II. The Basics

PYTHON PROGRAMMING TOPICS
I
•  Introduction to Python Programming
II
•  Python Basics
III
•  Controlling the Program Flow
IV
•  Program Components: Functions, Classes, Modules, and Packages
V
•  Sequences (List and Tuples), and Dictionaries
VI
•  Object-Based Programming: Classes and Objects
VII
•  Customizing Classes and Operator Overloading
VIII
•  Object-Oriented Programming: Inheritance and Polymorphism
IX
•  Randomization Algorithms
X
•  Exception Handling and Assertions
XI
•  String Manipulation and Regular Expressions
XII
•  File Handling and Processing
XIII
•  GUI Programming Using Tkinter

RUNNING A COMPUTER PROGRAM
Source
Translator
Target
Low-Level Language
Assembler
Machine Code
High-Level Language
Compiler
Interpreter

RUNNING A PYTHON PROGRAM
to write & run a Python program you need a Text Editor
and a Python Interpreter (preferably Version 2.x
since version 3.x is not yet mainstream)
 
Possible Ways (Common Ones)
1. Atom/Notepad++/Sublime Text and command prompt
2. Atom/Notepad++/Sublime Text and IDLE
3. IDLE 
4. PyCharm, PyScripter, Aptana Studio, NINJA IDE…

HELLO WORLD
as a salute to all programmers in the world, beginning
programmers usually print in the console the infamous Hello
World mystical line 
 
 

 
 
 

print “Hello World”

HELLO WORLD IN 2 LINES

print “Hello”
print “World”

in Python, the print statement will always
move the cursor to the next line after printing

HELLO WORLD, SUPRESSING NEWLINES

print “Hello”,
print “World”

A comma (,) will suppress the auto newline insertion
in print statements; it will add a space instead.

FORCING NEW LINES
 
 
 

 
 
 

print “Hello nWorld nPo!”

n = new line

FORCING NEW LINES & TABS
 
 
 

 
 
 

print “Hello ntWorld ntPo!”

t = tab

ESCAPE SEQUENCES
 
 
 

 
 
 

print “Hello ntWorld ntPo!”

t = tab

EXERCISE
Using Escape Sequences, print the following, including the
punctuations: 
 
“Mahal ko po si Migueeeel!”, sabi ni Amanda.  
 
“Hindi maari yan, lalo na’t si Miguel ay isang Halimaw!”, ang
tugon ng kanyang ina.

COMMENTS
comments don’t do anything except to serve as a
documentation part of a program 
 
use comments as often as you can because programmers
tend to forget what they’ve programmed after a month or so 
 
 

 
 
 

#this is a comment
print ‘Magandang Araw Po!’

#this function computes the sum of two integers
def sum(x, y):
...

RAW INPUT, TEXT
 
 
 

 
 
 

x = raw_input(“Unang Salita:”)
y = raw_input(“Pangalawang Salita:”)

print x + y

raw_input is a built-in function; it’s included in the standard
library & returns a string data type

RAW INPUT, TEXT TO INTEGER
 
 
 

 
 
 

x = int(raw_input(“Unang Numero:”))
y = int(raw_input(“Pangalawang Numero:”))

print x + y

int is a built-in function; it’s included in the standard library &
converts a string to integer

INPUT, AUTO TEXT TO INTEGER
 
 
 

 
 
 

x = input(“Unang Numero:”)
y = input(“Pangalawang Numero:”)

print x + y

input is a built-in function; it’s included in the standard library
& converts a string number to integer.

VARIABLE ASSIGNMENT
 
 
 

 
 
 

x = input(“Unang Numero:”)
y = input(“Pangalawang Numero:”)

sum = x + y

print “Ang sum po ay”, sum

results could be printed directly or assigned to a variable
before printing

MEMORY CONCEPTS
 
 
 

 
 
 

x = raw_input(“Unang Numero:”)
x = int(x)

print x

ASSOCIATIVITY
 
 
 

 
 
 

import arcpy

input_file = "D:/Project/PRTSAS/Geodatabases/
Market_Values/Pasong Tamo Creek/
GIS_Computed_Market_Values.shp"

rows = arcpy.SearchCursor(input_file)

STRING FORMATTING
1. Rounding-off floating-point values

2. Representing numbers in exponential notation  

3. Aligning a column of numbers  
 
4. Right-justifying and left-justifying outputs 

5. Inserting characters or strings at precise locations  
 
6. Displaying with fixed-size field widths and precision

COMMON ERROR
Error: inserting spaces between the pair of symbols: 
 
==, !=, >= and <=

COMMON ERROR
reversing the order of the pair of operators in any of the operators: !
=, <>, >= and <=

Error: writing them as =!, ><, => and =<

COMMON ERROR
Confusing the equality operator == with the assignment symbol =
is an error.  
 
The equality operator should be read “is equal to” and the
assignment symbol should be read “gets,” “gets the value of” or
“is assigned the value of.”  
 
In Python, the assignment symbol causes a syntax error when
used in a conditional statement.

KEYWORDS/RESERVED WORDS
They cannot be used as identifiers.

COMMON ERROR
Failure to insert a colon (:) in an if structure. 
 
Failure to indent the body of an if structure.

LINE CONTINUATION
A lengthy statement may be spread over several lines with the
backslash () line continuation character.  
 
If a single statement must be split across lines, choose breaking
points that make sense, such as after a comma in a print
statement or after an operator in a lengthy expression.

LINE CONTINUATION
 
 
 

 
 
 

import arcpy

input_file = "D:/Project/PRTSAS/Geodatabases/
Market_Values/Pasong Tamo Creek/
GIS_Computed_Market_Values.shp"

rows = arcpy.SearchCursor(input_file)

ZEN OF PYTHON (import this)
 
 
 

 
 
 

q  typing import this will yield an awesome narrative

PRACTICE EXERCISE 2
Write a program that requests the user to enter two numbers and
prints the sum, product, difference and quotient of the two numbers.

PRACTICE EXERCISE 3
Write a program that reads in the radius of a circle and prints the
circle’s diameter, circumference and area. Use the constant value
3.14159 for π. Do these calculations in output statements.

PRACTICE EXERCISE 4
Write a program that reads in two integers and determines and
prints whether the first is a multiple of the second.

PRACTICE EXERCISE 5
Write a program that reads in a 3-digit number, dissects the number
and prints the 3 individual numbers. 
 
For example, 214 will be printed as: 

Hundreds: 2 

Tens: 1 

Ones: 4

PRACTICE EXERCISE 5 | SOLUTION
a = 14
print "Tens:", a/10
print "Ones:", a%10

a = 214
print "Hundreds:", a/100
hundreds_remainder = a%100
print "Tens:", hundreds_remainder/10
tens_remainder = hundreds_remainder%10
print "Ones:", tens_remainder

PRACTICE EXERCISE 5 | DEBUGGING
a = 214
remainder_100 = a%100
print remainder_100
print "Tens:", remainder_100/10
remainder_10 = remainder_100%10
print "Ones:", remainder_10

PRACTICE EXERCISE 5 | DEBUGGING
a = 214

a = input(“Magbigay ng 3-digit na numero:”)

PRACTICE EXERCISE 6
Write a program that reads in 3 integers and determines and prints
the largest number.

a = 2
b = 1
c = 4
max = a
if b > max:
max = b
if c > max:
max = c
print max

a = input("Unang Numero Po:")
b = input("Pangalawang Numero Po:")
c = input("Pangatlong Numero Po:")
max = a
if b > max:
max = b
if c > max:
max = c
print max

PRACTICE EXERCISE 7
Write a program that reads in 3 integers and determines and prints
the smallest & largest numbers.

a = input("Unang Numero Po:")
b = input("Pangalawang Numero Po:")
c = input("Pangatlong Numero Po:")
max = a
min = a
if b > max:
max = b
if c > max:
max = c
print max
if b < min:
min = b
if c < min:
min = c
print min

The Amusing Evolution of a Programmer 
 
http://www.ariel.com.au/jokes/The_Evolution_of_a_Programmer.html

REFERENCES
q  Deitel, Deitel, Liperi, & Wiedermann - Python: How to Program (2001).
q  Disclaimer: Most of the images/information used here have no proper source
citation, and I do not claim ownership of these either. I don’t want to reinvent the
wheel, and I just want to reuse and reintegrate materials that I think are useful or
cool, then present them in another light, form, or perspective. Moreover, the
images/information here are mainly used for illustration/educational purposes
only, in the spirit of openness of data, spreading light, and empowering people
with knowledge. J

Python Programming - II. The Basics

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