Introduction to Python

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Contents

How to install Python on Linux
How to run a Python program
The basic of Python codes
Data expressions
Built-in functions in Python
Interactive input/output
Conditional statement for Python
Loop structure for Python
Creating your own functions
Python modules
Reading/writing files for Python
Error handling code
Object Oriented Programming (OOP)
Tkinter package for GNU programming

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The basic of Python codes

Type declaration can be omitted and simply input numbers or words in a variable. The following is an example:

mes = "Hello World!" print mes

After runnning the above, you can have

$ Hello World!

You can connect words as a sentence:

a="I " b="love " c="New Orleans." print a+b+c

The output will be

$ I love New Orleans.

For expression of strings, you can use either single or double quotation.

Using numbers without a decimal point is recognized as an integer. Combining decimal numbers and integers results in a float data type.

test = 8e3 + 7**7 print test

The out is following:

$ 831543.0

In python, the complex variables are simply expressed as x+yj.

u=3.0+8.0j v=1.5-9.2j print u*v

$ (78.1-15.6j)

The basic arithmetic operations are +, -, *, and /. The power is expressed by **. In addition to them, // gives rounded off values.

test2 = 10.0//3.0 print test2

$ 3.0

String parameters can be operated by arithmetic operators shown above. For example,

print "Never give up!\n" * 3

$ Never give up! $ Never give up! $ Never give up!

You do not have to declear the type of variables, but you can change it in the context of commands.

print 2 + int(3.0) print 7.0 + float(4)

$ 5 $ 11.0

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