Python Variables, Constants and Literals

    This Python tutorial will discuss Python variables, constants, and literals. What are they, what are their types, and how to use Python variables, constants, and literals?

    Python Variables

    In Python, variables are those entities used to store values of a particular data type. Simply put, whenever you create a variable, it occupies some space in the memory according to the value assigned to it. The Python interpreter allocates memory to the variable based on the data type. Variables are used to get references for the values. For example, if you have a variable x with a value of 40,000, then instead of writing 40,000, you can write x to use the value . 

    x=40000
print(x)

    #Output 

    40000

    Variable Declaration and Assignment

    Suppose you have some experience with other high-level programming languages, such as C++ or Java. In that case, you must have noticed that if you declare a variable, you must write its data type along with it before assigning a value. In Python, however, you do not need to declare a data type along with the variable. You can directly assign a value to it and the Python interpreter will understand the data type you have assigned to the variable.

    Let’s understand this with an example:

    C++ Python 
    int x;

// Variable declaration in C++
x=20;

// Variable assignment in C++
cout<<x;

    //Output of C++ 

    20

    		 
    x = 20 # we do not declare the type of variable in Python

print(x)

    #Output of Python Code 

    20

    In Python, we use equal to (=) to assign a value to a variable, known as an assignment operator . The variable should be on the left of the assignment operator and the value on the right. You do not have this feature of variable declaration in Python. Here, you have to assign some value, and if you do not assign a value to the variable, then the interpreter will throw an error. You can assign any value to the variable, whether it could be an object, an address, a number, a string, a function, a list, a class, a tuple, etc.

    Variable Overwrite

    You can overwrite the variable's value by assigning it a value again in a new line. Take the following example to understand it: 

    x = 20 # we have assigned a value 20 to a variable x
print(x)
x = 40 # Now we overwrite the value of x 20 by 40 now x has a value of 40
print(x)

    #Output 

    20 40

    Multiple Assignments

    Python gives you this cool feature of multiple assignments of the variable. You can assign multiple values to multiple variables with a single assignment operator. While using multiple assignments, be careful and remember that the number of values on the right of the Assignment operator should be equal to the number of variables on the left. Here is an example: 

    a, b, c, d="apple", "boy", "cat", "dog"
print(a)
print(b)
print(c)
print(d)

    #Output 

    apple
boy
cat
dog

    You can assign a single value to many variables in Python at once. e.g. 

    steve_age = mark_age = keral_age = milli_age =20
print(steve_age)
print(keral_age)

    #Output 

    20 20

    Python CONSTANTS?

    Unlike other programming languages, like C++ or Java, Python does not support constants. You can use the naming convention to capitalize ( PEP 8 ). According to it, if you write a variable in upper case, it is termed as a constant, but actually, it’s a variable, but we treat it as a constant.

    Let’s understand this with an example: 

    normal_variable_all_lower_case = 100
CONSTANT_ALL_UPPER_CASE = 20

    Though both are variables, the name in uppercase is a constant in the professional field.

    Convention Rules for Writing Variables and Constants:

    • Use a full variable name instead of a letter. For example, use values instead of v .
    • Always use lowercase while writing a variable name. e.g. variable=40.
    • Always use UPPERCASE while using a constant name. e.g. CONSTANT=40.
    • Never use a unique character while writing a variable name except for underscore (_).
    • Use underscores to separate the variable name. e.g. steve_age = 30

    Python Literals

    Literals can be defined as the data given to the variables and constants. This creates confusion. Let's understand it with an example: 

    string= "This is a Python string literal"

    Here in this example, we assign data, a string, to the variable string using an assignment operator. Here the text (“ This is a Python string literal”) is a string literal.

    Types of Literals in Python

    1. String Literals

    A given data to a variable or constant will be known as a string variable if the quotes surround it, and the quotes could be (“) or (‘). With the literal string, we can use the escape character with a special sign backslash (\).

    Example 

    string_literal_1="Hello World inside double quote"
string_literal_2='Hello world inside single quote'
string_literal_3="""multi
                      line
                      string"""
string_literal_4="using \
                   escape character for \
                   every next line"
print(string_literal_1)
print(string_literal_2)
print(string_literal_3)
print(string_literal_4)

    #Output 

    Hello World inside double quote
Hello world inside single quote
multi
line
string
using escape character for every next line

    2. Boolean Literals

    There are only two Boolean literals, True and False. 0 is considered as False. e.g. 

    bool_1=False
bool_2=True
print(bool_1)
print(bool_2)
print(0==False)

    #Outputs 

    False
True
True

    3. Numerical Literals

    Numerical literals are immutable, and there are three kinds of numerical literals:

    1. Integer,
    2. Float, and
    3. Complex.

    e.g. 

    integer = 23
float_contains_decimal_points= 23.0
complex_real_imag=23+7j
print(integer)
print(float_contains_decimal_points)
print(complex_real_imag.real)
print(complex_real_imag.imag)

    #Output 

    23
23.0
23.0
7.0

    4. Special Literal (None)

    Python has a particular literal known as None, which means nothing. 

    special_literal=None
print(special_literal)

    #Output 

    None

    5. Literal Collection

    The literal collection is the collection of literals. There are 4 types of literal collections:

    1. List,
    2. Dictionary,
    3. Sets, and
    4. Tuples.

    e.g. 

    list_1=[1,"String",True,None]
dictionary={1:"String","string":3,4:True}
sets={1,True,"string",2.3}
tuples=("string",True,["list1","list2"])
print(list_1)
print(dictionary)
print(sets)
print(tuples)

    #Output 

    [1, 'String', True, None]
{1: 'String', 'string': 3, 4: True}
{2.3, 1, 'string'}
('string', True, ['list1', 'list2'])

    Conclusion

    That was all about Python variables, constants, and literals. These are fundamental concepts in any programming language. Therefore, knowing them is essential to make the most out of a program .

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