Python Constants and Literals

In this post, we will learn about the constants and literals in Python.

Constants:

Assigning value to a constant in Python:

Declaration and assigning values to the constants:

PI=3.14
GRAVITY=9.8

Create a main file main.py:

import constant as cons
print(cons.PI)
print(cons.GRAVITY)

Output:​

In the above program, firstly we created a constant.py module file. After that, we assigned the constant value 3.14 and 9.8 to PI and GRAVITY respectively. Then, we created a main.py file and imported the constant module. After this, we print the values of PI and GRAVITY.

Rules of naming constants:

1. Constant should have a combination of letters in lowercase (a to z) or uppercase (A to Z) or digits (0 to 9) or an underscore (_). For example:

   Codes_Dope
   codes_dope
   CODES_DOPE
   _codes_dope7
   

2. Constant name should not start with a digit.
   
3. If we want to create a variable name having two words, we should use underscore to separate them. For example:

   MY_NAME
   CURRENT_SALARY
   

4. Generally, the constants value are declared using capital letters. This is done to differentiate them from variables.

   PI
   G
   MASS
   SPEED_OF_LIGHT
   TEMP
   

5. No other special character (!,#,^,@,$) is used except underscore(_) for declaring a constant.
   
6. We should create a name that makes sense. For example, GRAVITY makes more sense than G. It makes code easy to understand.

​Literals:

a=57
b=57.9
c="Hello World"
d=57+2j

Here 57, 57.9, "Hello World", 57+2j are considered as literals.

Literals are of five types:

1. Numeric Literal.
   
2. String Literal.
3. Boolean Literal.
4. Literal collections.
5. Special literals.

Numeric Literals:​

1. Integer.
   
2. Float.
3. Complex.

Integer:

a = 0b1000 #Binary Literals
b = 100    #Decimal Literal 
c = 0o561  #Octal Literal
d = 0x45f  #Hexadecimal Literal
print(a,b,c,d)

Output:​

Float:

a = 10.6 
b = 5.5e2
print(a,b)

Output:​

Complex:

a=5+3j

#real part is zero here
b=8j 
print(a.real,a.imag)
print(b.real.b.imag)

Output:

we use real literal (a.real) and imaginary literal (a.imag) to create real and imaginary parts of the complex numbers, respectively.

String Literals:

#in single quote
a='CodesDope'

#in double quotes
b=''CodesDope''

#in triple quotes”
c='''Codes
	Dope'''
print(a)
print(b)
print(c)

Output:

Character literal:

It is a type of string literal. In this a single character is surrounded by single or double quotes.​

a='b'
c="d"
print(a)
print(c)

Output:

​Boolean Literals:

a=(0==False)
b=(0==True)
c=5-False
d=True+7

print(a)
print(b)
print(c)
print(d)

Output:

​In python, True value is represented by 1 and False value is represented by 0.

In above program, a is true and b is false because 0 is equal to False. 

Similarly, we can use the True and False in numeric expressions as the values.

Value of c is 5 because false value is equal to 0. So, 5-0=0. Value of d is 8 because True value is equal to 1. So, 1+7=8.   

Literals Collection:

There are 4 different types of literals collection:

1. List literals.
2. Tuple literals.
3. Dict literals.
4. Set literals.

List Literals:

roll_nos=[5,6,7,8,'invalid']
fruits = ["apple", "mango", "orange"]

print(roll_nos)
print(fruits)

Output:

Tuple Literals:

number = (1,2,3,4) 
names=('Jack', 'John', 'Pam') 
  
print(number) 
print(names) 

Output:

Dictionary Literals:

student_1={'name':'Jack','roll_no':5,'age':18}
student_2={'name':'Pam','roll_no':25,'age':19}

print(student_1)
print(student_2)

Output:

Set Literals:

Set has no duplicate elements.

alphabets={'a','b','b','c'}
numbers={1,2,3,4}

print(alphabets)
print(numbers)

Output:

Here, we can see that the order of alphabets set is altered and the duplicate value of 'b' is not considered in the set. 

Special Literals:

balance = None
print(balance) 

Output:

Difference between variables, constants and literals:

Yeah! we finished this concept.

Now move to the next chapter.