Free Python Course Guide chapter

Output, variables and data

How Python displays information, stores values and updates a program’s state. This is the same chapter students can use in the Course Guide after signing in.

Fast reminder

Quick facts

String: Text stored between quotation marks.
Variable: A named place in memory that stores a value.
Assignment: Giving a value to a variable using =.
Sequence: Instructions carried out in order, usually from top to bottom.

Section 1

Displaying information

Use print() and predict the exact output of a sequence.

The print function

print() sends information to the console. Text is a string and needs matching quotation marks. Each call normally ends with a new line. Python is case-sensitive, so print and Print are different names.

Labels and values

A comma lets one print() call display several values with spaces between them. Keep calculations outside quotation marks if Python should evaluate them. print("Total:", 6 + 4) displays Total: 10; print("6 + 4") displays the text 6 + 4.

Worked example

A clear status report

Situation: Display a heading and a calculated total.

The statements run in order and the expression is calculated before it is displayed.

print("SCORE REPORT")
print("Total:", 8 + 7)

Expected output

SCORE REPORT
Total: 15

Section 2

Variables and assignment

Store values with meaningful names and update them as a program runs.

Names and values

An assignment such as score = 10 stores the integer 10 using the name score. The equals sign means assign, not “is mathematically equal to”. Choose names that explain the purpose of the value.

Changing state

A later assignment replaces the current value. In score = score + 1, Python reads the current value on the right, adds one and stores the new value back in score.

Worked example

Updating a score

Situation: A player begins with 12 points and gains 5.

The second assignment uses the old value to calculate the replacement value.

score = 12
score = score + 5
print("Score:", score)

Expected output

Score: 17

Specification link

OCR reference

This chapter supports OCR GCSE Computer Science J277, component J277/02.

2.2.1
2.2.2

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