Initialising variables in Python: Numeric Types, String and Boolean

This post covers some methods of initialising Numeric type (int, float, complex), String and Boolean data type variables in python.

This notebook is available here: https://github.com/AdityaGarg1995/BeginnerPython

Initialising Numeric Variables

Initialising Integer Variables

## Initialising integers
### Assigning a value explicitly
x = 9 ## Initialises x as integer with value = 9
y = -9 ## Initialises y as integer with value = -9

### Without assigning a value explicitly
z = int() ## Initialises z as integer with value = 0

print('Value of x = ')
print(x) 
print('Data type of x is: ')
print(type(x))

print('Value of y = ')
print(y)
print('Data type of y is: ')
print(type(y))

print('Value of z = ')
print(z)
print('Data type of z is: ')
print(type(z))

Integer Variable initialisation : Code and output

Initialising Float variables

## Initialising floats
### Assigning a value explicitly
x = 1.5 ## Initialises x as float with value = 1.5
y = -1.5 ## Initialises y as float with value = -1.5

### Without assigning a value explicitly
z = float() ## Initialises z as float with value = 0.0

print('Value of x = ')
print(x) 
print('Data type of x is: ')
print(type(x))

print('Value of y = ')
print(y)
print('Data type of y is: ')
print(type(y))

print('Value of z = ')
print(z)
print('Data type of z is: ')
print(type(z))

Float Variable initialisation : Code and output

Initialising Complex Number Variables

Reference: https://docs.python.org/3/library/functions.html#complex

## Initialise complex number

### Initialise complex number by explicitly providing real and imaginary values
x = complex (1, 5) 
y = complex (-1.5, 9.7)
z = complex (6.889, -9.006)


print('Value of x = ')
print(x) 
print('Data type of x is: ')
print(type(x))

print('Value of y = ')
print(y)
print('Data type of y is: ')
print(type(y))

print('Value of z = ')
print(z)
print('Data type of z is: ')
print(type(z))

### Initialise complex number using other variables for real and imaginary values

a = 1.5
b = 9.7

x = complex(a,b)
y = complex (-a, b)
z = complex (a, -b)

print('Value of x = ')
print(x) 
print('Data type of x is: ')
print(type(x))

print('Value of y = ')
print(y)
print('Data type of y is: ')
print(type(y))

print('Value of z = ')
print(z)
print('Data type of z is: ')
print(type(z))

### Initialise complex number using string input

x = complex('1+2j')
y = complex('1-2j')
z = complex('-1+2j')

print('Value of x = ')
print(x) 
print('Data type of x is: ')
print(type(x))

print('Value of y = ')
print(y)
print('Data type of y is: ')
print(type(y))

print('Value of z = ')
print(z)
print('Data type of z is: ')
print(type(z))

Complex Number Variable initialisation : Code and output [1]

Complex Number Variable initialisation : Code and output [2]

Complex Number Variable initialisation : Code and output [3]

Initialising String Variables

Strings are immutable sequences of Unicode code points. String literals are written in a variety of ways:

• Single quotes: 'allows embedded "double" quotes'
• Double quotes: "allows embedded 'single' quotes"
• Triple quoted: '''Three single quotes''', """Three double quotes""" → Triple quoted strings may span multiple lines — all associated whitespace will be included in the string literal.

Initialising non-empty single line string variables

x = 'Hello World' ## Initialises with single quotes
y = "Hello World" ## Initialises with double quotes

v = str('Hello World')  ## Initialise using constructor with single quotes
w = str("Hello World")  ## Initialise using constructor with double quotes

print('Value of x = ')
print(x) 
print('Data type of x is: ')
print(type(x))

print('Value of y = ')
print(y)
print('Data type of y is: ')
print(type(y))



print('Value of v = ')
print(v)
print('Data type of v is: ')
print(type(v))

print('Value of w = ')
print(w)
print('Data type of w is: ')
print(type(w))

Non-Empty Single line String Variable Initialisation

Initialising Multi-line String Variables

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Initialising by simply putting string in multiple lines will throw error

Initialising multi-line string variables is achieved using triple quoting: use three pairs of single or double quotes to enclose the string as described below.

## Initialise multi-line string variables --> Needs triple quoting

## Initialises multi-line string variable by triple quoting using single quotes
x = '''Hello 
World''' 
## Initialises multi-line string variable by triple quoting using single quotes
y = """Hello 
World"""


## Initialises multi-line string variable by triple quoting using single quotes
v = str('''Hello 
World''')
## Initialises multi-line string variable by triple quoting using single quotes
w = str("""Hello 
World""") 


print('Value of x = ')
print(x) 
print('Data type of x is: ')
print(type(x))

print('Value of y = ')
print(y)
print('Data type of y is: ')
print(type(y))



print('Value of v = ')
print(v)
print('Data type of v is: ')
print(type(v))

print('Value of w = ')
print(w)
print('Data type of w is: ')
print(type(w))

Multi-line String Variable initialisation

Initialising Empty String Variable

## Initialise empty string
x = '' ## Initialises with single quotes
y = "" ## Initialises with double quotes
z = str() ## Initialises using constructor


print('Value of x = ')
print(x) 
print('Data type of x is: ')
print(type(x))

print('Value of y = ')
print(y)
print('Data type of y is: ')
print(type(y))

print('Value of z = ')
print(z)
print('Data type of z is: ')
print(type(z))

Initialising Boolean Variables

Boolean variables can be initialised using the keywords True and False.

Additionally, all non-zero numeric types and non-empty strings evaluate to True if given as bool() constructor input.

## Intialising Boolean variables using True and False keywords
x = True
y = False

print('Value of x = ')
print(x) 
print('Data type of x is: ')
print(type(x))

print('Value of y = ')
print(y)
print('Data type of y is: ')
print(type(y))

## All non-zero numeric types and non-empty strings evaluate to True if given as bool() constructor input
### Initialising boolean using Numeric inputs to constructor
x = bool(20)
y = bool(-30)
z = bool(0)


print('Value of x = ')
print(x) 
print('Data type of x is: ')
print(type(x))

print('Value of y = ')
print(y)
print('Data type of y is: ')
print(type(y))

print('Value of z = ')
print(z)
print('Data type of z is: ')
print(type(z))

## All non-zero numeric types and non-empty strings evaluate to True if given as bool() constructor input

### Initialising boolean using Complex Number inputs to constructor

x = bool(complex(20, 30))
y = bool(complex(-10, -30))
z = bool(complex(0,0))


print('Value of x = ')
print(x) 
print('Data type of x is: ')
print(type(x))

print('Value of y = ')
print(y)
print('Data type of y is: ')
print(type(y))

print('Value of z = ')
print(z)
print('Data type of z is: ')
print(type(z))

## All non-zero numeric types and non-empty strings evaluate to True if given as bool() constructor input
### Initialising boolean using String inputs to constructor
x = bool('Hello')
y = bool("Hello")
z = bool('')


print('Value of x = ')
print(x) 
print('Data type of x is: ')
print(type(x))

print('Value of y = ')
print(y)
print('Data type of y is: ')
print(type(y))

print('Value of z = ')
print(z)
print('Data type of z is: ')
print(type(z))

Initialise Boolean using True and False Keywords

Initialise Boolean using Numeric Input to constructor [1]

Initialise Boolean using Numeric Input to constructor [2]

Initialise Boolean using String Input to constructor

Disallowed Variable Names

Variable names cannot start with a number — if so initialised, an error is thrown, as in below example.