Data types and conversions¶

Definition¶

A data type is the kind of data which will be stored in a variable. Common data types are string, integer, floating point number, character and Boolean.

Note

Python will automatically determine which data type it will store data as. You need to be aware of data types in order to convert data from one type to another.

Data types¶

Data type	Meaning	Examples
Integer	A whole number	`1`, `5`, `17`, `0`
Float	Floating point number A decimal/real number	`5.27`, `2.0`, `3.14`
Boolean	True or False	`True`, `False`
Char	A character - one letter or symbol, in Python this is a string)	`'H'`, `'7'`, `'g'`, `'@'`
String	A list of characters	`'Hello'`, `'Some text'`
List	A list (similar to an array)	`['Earth', 'Fire', 'Water']`

Type conversion / casting¶

Conversion function	Convert from what to what	Examples
`int()`	string or float to integer	`int('132')`, `int(132.0)`
`float()`	string or integer to float	`float('132')`, `float(132)`
`str()`	float or integer to string	`str(132)`

Easy example¶

age = 15
print('You are ' + str(age))

You are 15

Note

You can also use print('You are ', age) in Python to save needing to do the string conversion and concatenation.

Syntax¶

int(string)    #convert string to integer
int(float)     #convert float to integer
float(integer) #convert integer to float
float(string)  #convert string to float
str(integer)   #convert integer to string
str(float)     #convert float to string
type(value)    #find the type of the value given

Examples¶

Example 1 - Creating an integer¶

numberOfSweets = 10

numberOfSweets will be an integer which stores the value 10.

Example 2 - Creating a floating point number¶

height = 168.3

height will be a floating point number which stores the value 168.3.

Example 3 - Convert a number into a string for output¶

numberOfSweets = 10
print('You have ' + str(numberOfSweets) + ' sweets')

You have 10 sweets

Example 4 - Convert a string into a number for arithmetic¶

numberOfSweetsNow = 10
buySweets = input('How many sweets do you buy? ')
totalSweets = numberOfSweetsNow + int(buySweets)
print(str(totalSweets))

How many sweets do you buy? 15
25

Example 5 - Converting variables for inputs and outputs¶

ageYears = input('How old are you in years? ')
ageWeeks = int(ageYears) * 52
print('You are ' + str(ageWeeks) + ' weeks old.') #convert ageWeeks to a string

How old are you in years? 10
You are 520 weeks old.

Note

You can also do type conversions in the same line of code as an input. For example, ageYears = int(input('How old are you in years? ')).

Example 6 - Find out the data type of a value¶

print(type('hello'))

<class 'str'>

Example 7 - Find out the data type of a variable¶

keyColours = ['red', 'green', 'blue']
print(type(keyColours))

<class 'list'>

Example 8 - Find the ASCII character number of a character¶

print(ord('A'))
print(ord('a'))
print(ord('b'))

65
97
98

Example 9 - Find the character of an ASCII number¶

print(chr(65))

Key points¶

Note

Python can use both ‘ and ” for strings. So "hello" and 'hello' are both exactly the same.

Hint

You can find out what data type a value or a variable is storing by using type(value).

Note

Python doesn’t have a different data type for strings and characters. It treats a character as a string of length one.