9. Selection constructs and writing readable code: elif

Leaning Outcomes

You will learn to:

Use ELIF

Write readable code

Activity 8.1

Using elif

This program simulates a fortune cookie. A random number is used to decide your ‘fortune’.

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Copy and run this program.

# a random number is given by the randint() function

import random

answer= random.randint(1,6)

if answer == 1:

​print("You will make a new friend this week")

elif answer == 2:

​print("You will do well in your GCSEs")

elif answer == 3:

​print("You will find something you thought you’d lost")

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The program is not yet complete. Include your own ‘fortunes’ for the numbers 4, 5 and 6.

Note: random.randint(1,6) is a function that returns a random number between 1 and 6. The ‘import random’ command allows the program to access the random.randint() function.

Activity 8.2

Writing readable code: a style guide

Program code is read more often that it is written. Here are some guidelines on how to write Python code so that it is easy to read.

A style guide for Python code

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Indent by four spaces for each indentation level.

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Use blank lines to separate different parts of the program.

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Use two blank lines to separate functions.

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Choose meaningful names for variables, using CamelCase or with words separated by underscores.

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Put imports at the top of the file.

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Include one space around each side of an assignment and other operators.

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Use complete sentences with the first word capitalised for comments.

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Write comments that add clarity and explain what the program does. Do not simplyrepeat what the code already says.

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Write function names in lowercase, with words separated by underscores.

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Use meaningful function names which describe the purpose of the function.

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Write constants in CAPITAL_LETTERS.

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Use meaningful constant names, which describe the purpose of the constant.

Note: Functions are subprograms which start with the “deffunction_name():. Constants are variables whose value never changes. You will be covering functions in later lessons.  

For more detail see http://www.python.org/dev/peps/pep-0008/

Apply the rules in the style guide above for this Python code.

def a(s):

if s<50:

print("You have lost")

else:

print("You have won")  

Activity 8.3

Select some of your programs and make them more readable using the rules in the style guide.Lesson 9 activities