Data types
- Integer: a whole number, such as 42. Real (also called float): a number with a decimal part, such as 3.14. Boolean: True or False.
- Character: a single letter, digit or symbol, such as 'A'. String: a sequence of characters, such as "Hello".
- Choosing the right type saves memory and avoids errors. A phone number is stored as a string, because it can start with 0 and is never used in calculations.
Casting
- Casting converts data from one type to another: int("42") gives the integer 42, and str(42) gives the string "42".
- Input from the keyboard is a string, so cast it to a number before doing maths with it.
Arrays
- An array stores several values of the same type under one name. Each value has an index, which usually starts at 0: names[0] is the first item.
- A 2D array is like a table, and needs two indexes, such as grid[row][column]. Check the question to see which index comes first.
- In many languages an array has a fixed size. Python uses lists, which can grow and shrink.
Records
- A record groups related data of different types into fields. A student record might have a name (string), an age (integer) and whether they have paid (Boolean).
Key terms
- Integer
- A whole number.
- Real
- A number with a decimal part (also called a float).
- Boolean
- A data type with only two values: True or False.
- Character
- A single letter, digit or symbol.
- String
- A sequence of characters, such as a word or sentence.
- Casting
- Converting data from one data type to another.
- Array
- A data structure that stores several values of the same type under one name.
- Index
- The position of an item in an array, usually counted from 0.
- Record
- A data structure that groups related fields of different types.