python programming - ii. the basics
DESCRIPTION
Feel free to download the material for offline viewing later, better images' resolutions, and crispier fonts.TRANSCRIPT
Engr. Ranel O. Padon
PYTHON PROGRAMMINGII. 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 CodeHigh-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. Notepad++/Sublime Text and command prompt
2. Notepad++/Sublime Text and IDLE
3. IDLE
4. PyScripter, PyCharm, 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 \n\tWorld \n\tPo!”
\t = tab
ESCAPE SEQUENCES
print “Hello \n\tWorld \n\tPo!”
\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 commentprint ‘Magandang Araw Po!’
#this function computes the sum of two integersdef 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
ARITHMETIC OPERATIONS
TRUE DIVISION RESULT
TRUE DIVISION RESULT
THE PEMMDAS PRECEDENCE
THE PEMMDAS PRECEDENCE
THE PEMMDAS PRECEDENCE
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
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
STRING FORMATTING
STRING FORMATTING
STRING FORMATTING
STRING FORMATTING
STRING CONVERSION SPECIFIER
STRING CONVERSION SPECIFIER
RELATIONAL OPERATOR
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.
RELATIONAL OPERATOR
RELATIONAL OPERATOR
RELATIONAL OPERATOR
PROPER INDENTATION
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)
PRACTICE EXERCISE 1
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 6
Write a program that reads in 3 integers and determines and prints
the largest number.
PRACTICE EXERCISE 7
Write a program that reads in 3 integers and determines and prints
the smallest & largest numbers.
The Amusing Evolution of a Programmer
http://www.ariel.com.au/jokes/The_Evolution_of_a_Programmer.html
REFERENCES
Deitel, Deitel, Liperi, & Wiedermann - Python: How to Program (2001).
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.