Python Variables, Constants and Literals

By | August 27, 2021
Python Variables, Constants & Literals

In this Python tutorial, we are going to discuss Python variables, constants, and literals. What are they, their types, and how to use Python variables, constants, and literals.

Python Variables

In Python, variables are those entities that are used to store values of a particular data type. In simple words, whenever you create a variable, it occupies some space in the memory according to the value assigned to it.

Vamware

Based on the data type, the Python interpreter allocates memory to the variable. Variables are used to get references for the values. For example, if you have a variable x with a value 40,000 then instead of writing 40,000 you can just write x to use the value.

x=40000
print(x)

#Output

40000

Variable Declaration and Assignment

If you have some experience with other high-level programming languages, such as C++ or Java, you must have noticed that if you declared a variable, you need to 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 itself 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 which is 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, either 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 value of the variable 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 the multiple assignments be careful and must remember that the number of values on the right of the Assignment operator should be equal to the number of variables on the left of the Assignment operator. 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

In Python, you can assign a single value to many variables 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 variable name written in uppercase is termed as 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 special character while writing a variable name except for underscore (_).
  • Use underscore to separate the variable name. e.g. steve_age = 30

Python Literals

Literals can be defined as the data is 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, which is 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 it is surrounded by the quotes and the quotes could be (“) or (‘). With the string literal, we can use the escape character by using a special sign backslash (\).

e.g.

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 3 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 special 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 important to make the most out of a program.

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