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.
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.
Choose a valid name
Use a name such as total_score that explains what is stored. Names can contain letters, digits and underscores, but cannot start with a digit or contain spaces. score2 is valid; 2score is not. A name cannot be a keyword such as for, and uppercase and lowercase letters are different.
Specification link
OCR reference
This chapter supports OCR GCSE Computer Science J277, component J277/02.
- 2.2.1
- 2.2.2