2. Data Types

See: https://www.w3schools.com/python/python_datatypes.asp

Data Type

Example

Description

Integers

4 or 0 or -5

Positive and negative whole numbers

Floats

3.14

Numbers with a decimal point

Strings

"Hello" or '2.5'

Characters enclosed by single or double quotation marks

Booleans

True or False

Values representing true and false values

Some common built-in data types are:

Text Type:

str

Numeric Types:

int, float

Sequence Types:

list, tuple, range

Mapping Type:

dict

Set Types:

set, frozenset

Boolean Type:

bool

None Type:

NoneType

2.1. Strings

A string is a sequence of characters surrounded by either single quotation marks (’ ‘), or double quotation marks (” “).
Text with quotes within it can use done using the other quote mark.
e.g. “it’s”
e.g. ‘Jim said “Go home”, then left.’
Text with both quotes within it can use done using triple quotes.
‘’’My favourite quote from Jim’s essay was “Go home”. Short and sharp.’’’
Escaping via can be used to force the quote to be used literally.
e.g. ‘it's’
Triple quotes are used for documentation strings. Triple single or triple double quotes can be used.
Triple quotes can also be used for multi line strings.
e.g. ‘’’n is an integer’’’
e.g. “””angle is a float from 0 to 90”””

2.2. Numbers

Numbers are written without quotes.
An integer is a whole number.
e.g. 2
A float is a decimal.
e.g. 3.5

2.3. Booleans

Booleans have the value True or False.

2.4. Types

The type() function can be used to get the data type for a variable.

# String
print(type('hello'))   # <class 'str'>

# Integer
print(type(1))         # <class 'int'>

# Float
print(type(1.64))      # <class 'float'>

# Boolean
print(type(True))      # <class 'bool'>

# None
print(type(None))      # <class 'NoneType'>

Questions

  1. Predict the output from print(type('123')).

  2. Predict the output from print(type(123)).

  3. Predict the output from print(type('False')).

2.5. Type casting

See: https://www.w3schools.com/python/python_casting.asp

Data types can’t be mixed.
They need to be converted to the same type so that they can be used together.
The conversion of one type to another is called type casting.
An integer can be converted to a string using the str() function.
The premierships integer is converted to a string so it can be combined with the rest of the strings for printing.
team = 'Richmond'
premierships = 11
print(team + ' has won ' + str(premierships) + ' premierships.')

int() converts a string consisting of an integer to an integer number

c = int("3")      # c will be 3

float() converts a string consisting of a decimal to a decimal number

g = float("4.23") # g will be 4.23

str() converts a number to a string with a number in it

j = str(3.01) # j will be "3.01"

Questions

  1. Predict the output from print(int(2.5)).

  2. Predict the output from print(int("3")).

  3. Predict the output from print(float(1)).

  4. Predict the output from print(float("4.23")).

  5. Predict the output from print(str(3.01)).