Modules and Functions, Lecture notes of Web Programming and Technologies

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ESCI 386 – Scientific Programming,

Analysis and Visualization with

Python

Lesson 9 - Modules and Functions

Defining and Using a Function

def sphere_area(r):

pi = 3.

return 4pir**

>>> sphere_area(5)

Lambda Operator

• Python also has a simple way of defining a one-line function.
• These are created using the Lambda operator.
• The code must be a single, valid Python statement.
• Looping, if-then constructs, and other control statements cannot be use in Lambdas.

bar = lambda x,y: x + y bar(2,3) 5 cube_volume = lambda l, w, h: lwh cube_volume(2, 4.5, 7)

Modules

 A module is simply a collection of functions and

other Python statements that can be loaded

using the import command, and then accessed.

 In addition to functions being defined within

modules, constants can also be defined.

 The functions and constants are accessed by

prefacing them with the name of the module.

Module Example

pi = 3.

def area(r): return 4.0pir**

def volume(r): return (4.0/3.0)pir**

import Sphere Sphere.pi

Sphere.area(5)

Sphere.volume(5)

Saved to ‘Sphere.py’

Namespace Consideration

• We can import the module using a shorter

alias if we want.

import Sphere as s s.area(4)

Namespace Consideration (cont.)

• We can use * to import all constants and

functions from a module without having to use

the module name.

from Sphere import * area(4)

• However, this is not recommended!
• You might inadvertently import two functions with the same

name from two different modules, which can cause confusion.

Documentation Strings

• A document string is an optional string at the

beginning of a module or function that describes the module or function and its use.

• The document string can be accessed via the

doc attribute.

• It is a good idea to include at least a one-line document

string in your functions and modules.

• The documents string should show usage and explain any

options.