Python 3 - Variable Types

#!/usr/bin/python3

counter = 100          # An integer assignment
miles   = 1000.0       # A floating point
name    = "John"       # A string

print (counter)
print (miles)
print (name)

Here, 100, 1000.0 and "John" are the values assigned to counter, miles, and name variables, respectively. This produces the following result −

100
1000.0
John

Multiple Assignment

Python allows you to assign a single value to several variables simultaneously.

For example −

a = b = c = 1

Here, an integer object is created with the value 1, and all the three variables are assigned to the same memory location. You can also assign multiple objects to multiple variables. For example −

a, b, c = 1, 2, "john"

Here, two integer objects with values 1 and 2 are assigned to the variables a and b respectively, and one string object with the value "john" is assigned to the variable c.

Standard Data Types

The data stored in memory can be of many types. For example, a person s age is stored as a numeric value and his or her address is stored as alphanumeric characters. Python has various standard data types that are used to define the operations possible on them and the storage method for each of them.

Python has five standard data types −

Numbers

String

List

Tuple

Dictionary

Python Numbers

Number data types store numeric values. Number objects are created when you assign a value to them. For example −

var1 = 1
var2 = 10

You can also delete the reference to a number object by using the del statement. The syntax of the del statement is −

del var1[,var2[,var3[....,varN]]]]

You can delete a single object or multiple objects by using the del statement.

For example −

del var
del var_a, var_b

Python supports three different numerical types −

int (signed integers)

float (floating point real values)

complex (complex numbers)

All integers in Python3 are represented as long integers. Hence, there is no separate number type as long.

Examples

Here are some examples of numbers −

A complex number consists of an ordered pair of real floating-point numbers denoted by x + yj, where x and y are real numbers and j is the imaginary unit.

Python Strings

Strings in Python are identified as a contiguous set of characters represented in the quotation marks. Python allows either pair of single or double quotes. Subsets of strings can be taken using the spce operator ([ ] and [:] ) with indexes starting at 0 in the beginning of the string and working their way from -1 to the end.

The plus (+) sign is the string concatenation operator and the asterisk (*) is the repetition operator. For example −

#!/usr/bin/python3

str =  Hello World! 

print (str)          # Prints complete string
print (str[0])       # Prints first character of the string
print (str[2:5])     # Prints characters starting from 3rd to 5th
print (str[2:])      # Prints string starting from 3rd character
print (str * 2)      # Prints string two times
print (str + "TEST") # Prints concatenated string

Hello World!
H
llo
llo World!
Hello World!Hello World!
Hello World!TEST

#!/usr/bin/python3

pst = [  abcd , 786 , 2.23,  john , 70.2 ]
tinypst = [123,  john ]

print (pst)          # Prints complete pst
print (pst[0])       # Prints first element of the pst
print (pst[1:3])     # Prints elements starting from 2nd till 3rd 
print (pst[2:])      # Prints elements starting from 3rd element
print (tinypst * 2)  # Prints pst two times
print (pst + tinypst) # Prints concatenated psts

[ abcd , 786, 2.23,  john , 70.200000000000003]
abcd
[786, 2.23]
[2.23,  john , 70.200000000000003]
[123,  john , 123,  john ]
[ abcd , 786, 2.23,  john , 70.200000000000003, 123,  john ]

#!/usr/bin/python3

tuple = (  abcd , 786 , 2.23,  john , 70.2  )
tinytuple = (123,  john )

print (tuple)           # Prints complete tuple
print (tuple[0])        # Prints first element of the tuple
print (tuple[1:3])      # Prints elements starting from 2nd till 3rd 
print (tuple[2:])       # Prints elements starting from 3rd element
print (tinytuple * 2)   # Prints tuple two times
print (tuple + tinytuple) # Prints concatenated tuple

( abcd , 786, 2.23,  john , 70.200000000000003)
abcd
(786, 2.23)
(2.23,  john , 70.200000000000003)
(123,  john , 123,  john )
( abcd , 786, 2.23,  john , 70.200000000000003, 123,  john )

#!/usr/bin/python3

tuple = (  abcd , 786 , 2.23,  john , 70.2  )
pst = [  abcd , 786 , 2.23,  john , 70.2  ]
tuple[2] = 1000    # Invapd syntax with tuple
pst[2] = 1000     # Vapd syntax with pst

#!/usr/bin/python3

dict = {}
dict[ one ] = "This is one"
dict[2]     = "This is two"

tinydict = { name :  john , code :6734,  dept :  sales }

print (dict[ one ])       # Prints value for  one  key
print (dict[2])           # Prints value for 2 key
print (tinydict)          # Prints complete dictionary
print (tinydict.keys())   # Prints all the keys
print (tinydict.values()) # Prints all the values

This is one
This is two
{ name :  john ,  dept :  sales ,  code : 6734}
dict_keys([ name ,  dept ,  code ])
dict_values([ john ,  sales , 6734])