Introduction to python

Why do people use Python?
• Software Quality:
Python is designed to be readable, and hence maintainable.
• Developer productivity:
Python code is typically 1/3 to 1/5 the size of equivalent C++ or JAVA
code

What can I do with Python?
• System Programming
• GUIs
• Internet Scripting
• Database Programming
• Games, Images, AI, XML and more

What are Python’s Technical Strength
• It’s OO
• It’s free
• It’s Portable
• It’s Powerful
• It’s Easy to use
• It’s Easy to learn

What is the Downside of Python?
• Perhaps the only downside to Python is that the execution speed
may not always as fast as compiled languages such as C and C++
• Python is not compiled all the way down to binary machine code, it
compiled to byte code instead.

Who Uses Python Today?
• Google and Yahoo currently use Python in Internet service
• IBM use Python for hardware testing
• Industrial Light and Magic use Python in the production of movie
animation
• For more details, visit www.python.org

Install Python
• Go to http://www.python.org/download/releases/3.2/ and
download Python3.2, then select Windows x86 MSI Installer
(3.2) or Windows X86-64 MSI Installer (3.2)

Install Python
• Or you can search for Python, choose “Download” and then
select Python 3.2 Windows x86 MSI Installer or Python 3.2
Windows X86-64 MSI Installer

Hello World Program
• Implement by three different languages
• In C
• In JAVA
• In Python

“Hello World” in C
main()
{
printf("hello, worldn");
}

“Hello World” in JAVA
class myfirstjavaprog
{
public static void main(String args[])
{
System.out.println("Hello World!");
}
}

“Hello World” in Python
print (“Hello World!!”)

Be familiar with Python
>>> print ("Hello, World! ")
Hello, World!
>>> 10 + 25
35
>>> 124 – 125
-1
>>> 1/3
0.333333333333333

• Python command print – Displays data, values, and expressions
• The single and double quotation mark string objects, which are
collections of texts surrounded by quotes.
Some Python commands

>>> print ("Hello, World! ")
Hello, World!
>>> "hello"
'hello'
>>> "world"
'world'
>>> "hello"+"world"
'helloworld'

>>> "hello" * 3
'hellohellohello'
>>> "hello" * 300

>>> width = 20
>>> height = 45
>>> area = width * height
>>> area
900
Declare a variable and assign its
value Example: Area of a
rectangle

>>> a=3
>>> b=4
>>> a+1
>>> b*3
>>> b/3
>>> b/3.0
>>> b**2
>>> 2+4.0
>>> 2.0**b
What are the outputs? Why?

How do you run programs?
Three different methods:
• 1. Interactive Coding
• 2. Files (such as NotePad, WordPad)
• 3. Integrated Development Environment (IDE)

Create and run a program in the
Python IDLE
• From File -> New Window
• Type your program
print ("Hello, World! ")
• Save your program
(Give a name you like, such as test.py)
• Run the program
(by selecting the Run Module or pressing the F5 key)

Your first Python program- hello.py
# This program says hello and asks for my name.
hello = 'Hello world! '
print(hello)
print('What is your name?')
myName = input()
print('It is good to meet you, ' + myName)

hello.py executed sequentially
# This program says hello and asks for my name.
Any text following a # sign is a comment. Comments are not
for the computer, but for you, the programmer.
1.hello = 'Hello world! ' # assign the string to a name
2.print(hello) # call the print( ) function
3.print('What is your name?') # call the print( ) function
4.myName = input() # call the input( ) function
5.print('It is good to meet you, ' + myName)

Introduction to python

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