Python Data Types

Python Data Types

Variables can hold values of different data types. Python is a dynamically typed language hence we need not define the type of the variable while declaring it. The interpreter implicitly binds the value with its type.
Python enables us to check the type of the variable used in the program. Python provides us the type() function which returns the type of the variable passed.
Consider the following example to define the values of different data types and checking its type.
A=10  
b="Hi Python"  
c = 10.5  
print(type(a));   
print(type(b));   
print(type(c));   

Output:
<type 'int'>
<type 'str'>
<type 'float'>

Standard data types
A variable can hold different types of values. For example, a person's name must be stored as a string whereas its id must be stored as an integer.
Python provides various standard data types that define the storage method on each of them. The data types defined in Python are given below.
1.     Numbers
2.     String
3.     List
4.     Tuple
5.     Dictionary
In this section of the tutorial, we will give a brief introduction of the above data types. We will discuss each one of them in detail later in this tutorial.

Numbers

Number stores numeric values. Python creates Number objects when a number is assigned to a variable. For example;
1.     a = 3 , b = 5  #a and b are number objects  
Python supports 4 types of numeric data.
1.     int (signed integers like 10, 2, 29, etc.)
2.     long (long integers used for a higher range of values like 908090800L, -0x1929292L, etc.)
3.     float (float is used to store floating point numbers like 1.9, 9.902, 15.2, etc.)
4.     complex (complex numbers like 2.14j, 2.0 + 2.3j, etc.)
Python allows us to use a lower-case L to be used with long integers. However, we must always use an upper-case L to avoid confusion.
A complex number contains an ordered pair, i.e., x + iy where x and y denote the real and imaginary parts respectively).

String

The string can be defined as the sequence of characters represented in the quotation marks. In python, we can use single, double, or triple quotes to define a string.
String handling in python is a straightforward task since there are various inbuilt functions and operators provided.
In the case of string handling, the operator + is used to concatenate two strings as the operation "hello"+" python"returns "hello python".
The operator * is known as repetition operator as the operation "Python " *2 returns "Python Python ".
The following example illustrates the string handling in python.
str1 = 'hello javatpoint' #string str1  
str2 = ' how are you' #string str2  
print (str1[0:2]) #printing first two character using slice operator  
print (str1[4]) #printing 4th character of the string  
print (str1*2) #printing the string twice  
print (str1 + str2) #printing the concatenation of str1 and str2  

OUTPUT 
he
o
hello javatpointhello javatpoint
hello javatpoint how are you
.

List

Lists are similar to arrays in C. However; the list can contain data of different types. The items stored in the list are separated with a comma (,) and enclosed within square brackets [].
We can use slice [:] operators to access the data of the list. The concatenation operator (+) and repetition operator (*) works with the list in the same way as they were working with the strings.
Consider the following example.
l  = [1, "hi", "python", 2]  
print (l[3:]);  
print (l[0:2]);  
print (l);  
print (l + l);  
print (l * 3);   
Output:
[2]
[1, 'hi']
[1, 'hi', 'python', 2]
[1, 'hi', 'python', 2, 1, 'hi', 'python', 2]
[1, 'hi', 'python', 2, 1, 'hi', 'python', 2, 1, 'hi', 'python', 2]

Tuple

A tuple is similar to the list in many ways. Like lists, tuples also contain the collection of the items of different data types. The items of the tuple are separated with a comma (,) and enclosed in parentheses ().
A tuple is a read-only data structure as we can't modify the size and value of the items of a tuple.
Let's see a simple example of the tuple.
t  = ("hi", "python", 2)  
print (t[1:]);  
print (t[0:1]);  
print (t);  
print (t + t);  
print (t * 3);   
print (type(t))  
t[2] = "hi";  
Output:
('python', 2)
('hi',)
('hi', 'python', 2)
('hi', 'python', 2, 'hi', 'python', 2)
('hi', 'python', 2, 'hi', 'python', 2, 'hi', 'python', 2)
<type 'tuple'>
Traceback (most recent call last):
  File "main.py", line 8, in <module>
    t[2] = "hi";
TypeError: 'tuple' object does not support item assignment

Dictionary

Dictionary is an ordered set of a key-value pair of items. It is like an associative array or a hash table where each key stores a specific value. Key can hold any primitive data type whereas value is an arbitrary Python object.
The items in the dictionary are separated with the comma and enclosed in the curly braces {}.
Consider the following example.
d = {1:'Jimmy', 2:'Alex', 3:'john', 4:'mike'};   
print("1st name is "+d[1]);  
print("2nd name is "+ d[4]);  
print (d);  
print (d.keys());  
print (d.values());  
Output:
1st name is Jimmy
2nd name is mike
{1: 'Jimmy', 2: 'Alex', 3: 'john', 4: 'mike'}
[1, 2, 3, 4]
['Jimmy', 'Alex', 'john', 'mike']
 

Python Keywords
Python Keywords are special reserved words which convey a special meaning to the compiler/interpreter. Each keyword have a special meaning and a specific operation. These keywords can't be used as variable. Following is the List of Python Keywords.
True
False
None
and
as
asset
def
class
continue
break
else
finally
elif
del
except
global
for
if
from
import
raise
try
or
return
pass
nonlocal
in
not
is
lambda


Python Literals

Literals can be defined as a data that is given in a variable or constant.
Python support the following literals:
I. String literals:
String literals can be formed by enclosing a text in the quotes. We can use both single as well as double quotes for a String.
Eg:
"Aman" , '12345'
Types of Strings:
There are two types of Strings supported in Python:
a).Single line String- Strings that are terminated within a single line are known as Single line Strings.
Eg:
>>> text1='hello'  
b).Multi line String- A piece of text that is spread along multiple lines is known as Multiple line String.
There are two ways to create Multiline Strings:
1). Adding black slash at the end of each line.
Eg:
>>> text1='hello\  
user'  
>>> text1  
'hellouser'  
>>>  
2).Using triple quotation marks:-
Eg:
>>> str2='''''welcome 
to 
SSSIT'''  
>>> print str2  
welcome  
to  
SSSIT  
>>>  
II.Numeric literals:
Numeric Literals are immutable. Numeric literals can belong to following four different numerical types.
Int(signed integers)
Long(long integers)
float(floating point)
Complex(complex)
Numbers( can be both positive and negative) with no fractional part.eg: 100
Integers of unlimited size followed by lowercase or uppercase L eg: 87032845L
Real numbers with both integer and fractional part eg: -26.2
In the form of a+bj where a forms the real part and b forms the imaginary part of complex number. eg: 3.14j
III. Boolean literals:
A Boolean literal can have any of the two values: True or False.
IV. Special literals.
Python contains one special literal i.e., None.
None is used to specify to that field that is not created. It is also used for end of lists in Python.
Eg:
>>> val1=10  
>>> val2=None  
>>> val1  
10  
>>> val2  
>>> print val2  
None  
>>>  
V.Literal Collections.
Collections such as tuples, lists and Dictionary are used in Python.
List:
  • List contain items of different data types. Lists are mutable i.e., modifiable.
  • The values stored in List are separated by commas(,) and enclosed within a square brackets([]). We can store different type of data in a List.
  • Value stored in a List can be retrieved using the slice operator([] and [:]).
  • The plus sign (+) is the list concatenation and asterisk(*) is the repetition operator.
Eg:
>>> list=['aman',678,20.4,'saurav']  
>>> list1=[456,'rahul']  
>>> list  
['aman', 678, 20.4, 'saurav']  
>>> list[1:3]  
[678, 20.4]  
>>> list+list1  
['aman', 678, 20.4, 'saurav', 456, 'rahul']  
>>> list1*2  
[456, 'rahul', 456, 'rahul']  
>>>  

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