Chapter 15. Modules

1. Chapter 15. Modules Dr. Bernard Chen Ph.D. University of Central Arkansas Spring 2012

2. Modules • Nodules are the highest level program organization unit, which packages program codes and data for reuse • Actually, each “file” is a module (Look into Lib in Python)

3. Why Use Modules? • Modules provide an easy way to organize components into a system, by serving as packages of names • Modules have at least three roles: • Code Reuse • Implementing shared services or data • Make everything “lives” in a Module

4. Module Creation • To define a module, use your text editor to type Python code into a text file • You may create some functions or variables in that file • You can call modules anything, but module filenames should end in .py suffix

5. Modules Usage • Clients can use the module file we just wrote by running “import” statement >>> import math >>> import random >>> import module1 # assume this is the file name we saved

6. Modules examples We will create two modules: module1 and module2 module2 will import data and functions from module1

7. module1.py print “First line of module1” def print_out(aa): print aa*3 x=1 y=2

8. module2.py print “First line of module2” import module1 module1.print_out(“Hello World!! ”) # Use module1’s function print module1.x, module1.y # Reference module1’s variable x=10 y=20 print x, y

9. module2 output • The result of execute this program is: • Hello World!! Hello World!! Hello World!! • 1 2 • 10 20

10. module3.py • You may import as many modules as you like, for example: import module1 import module2 print module1.x print module2.x • The result of execute this program is: 1 10

11. Important Notice • Import Happen Only ONCE If you try to import a module for the second time, Python will NOT execute it

12. Class Practice • Create two modules, each module has two functions and two variables • Create a third program which calls all functions and prints all variables in module1 and module2 you created