Python Program to Convert Octal to Decimal

This article is created to cover some programs in Python, to convert octal number entered by user to its equivalent decimal value. Here are the list of programs:

Note - Before creating these programs, if you're not aware about steps used for the conversion, then refer to Octal to Decimal Steps, Formula, Example to get every required things about the topic.

Octal to Decimal using while Loop

To convert octal to decimal number in Python, you have to ask from user to enter a number in octal number system, then convert that number into its equivalent decimal value as shown in the program given below:

The question is, write a Python program to convert octal to decimal using while loop. Here is its answer:

print("Enter the Octal Number: ")
octnum = int(input())

chk = 0
i = 0
decnum = 0
while octnum!=0:
    rem = octnum%10
    if rem>7:
        chk = 1
        break
    decnum = decnum + (rem * (8 ** i))
    i = i+1
    octnum = int(octnum/10)

if chk == 0:
    print("\nEquivalent Decimal Value =", decnum)
else:
    print("\nInvalid Input!")

Here is the initial output produced by this Python program:

octal to decimal python

Now supply the input say 1357 as octal number, and press ENTER key to convert and print its equivalent decimal value as shown in the snapshot given below:

convert octal to decimal python

Here is another sample run with octal number input 961:

python convert octal to decimal

Note - 9 is an invalid octal digit.

The dry run of above program with user input 1357 goes like:

Octal to Decimal using int()

This program uses int() method to convert octal number to decimal. The int() method returns integer (decimal) equivalent of value passed as its argument. The end= used in the program given below, to skip printing of an automatic newline using print():

print("Enter the Octal Number: ", end="")
onum = input()

dnum = int(onum, 8)
print("\nEquivalent Decimal Value =", dnum)

Here is its sample run with user input 124:

python convert octal to decimal

Octal to Decimal using Function

This program is created using user-defined function named OctToDec(). This function takes a value (octal) as its argument and returns its decimal equivalent using int() method.

def OctToDec(o):
    return int(o, 8)

print("Enter the Octal Number: ", end="")
onum = input()

dnum = OctToDec(onum)
print("\nEquivalent Decimal Value =", dnum)

Octal to Decimal using Class

This program is created using a class, an object-oriented feature of Python. In this program, an object obj is created of class fresherearth to access its member function OctToDec() using dot (.) operator. The member function OctToDec() returns the decimal equivalent of octal value passed as its argument.

class fresherearth:
    def OctToDec(self, o):
        return int(o, 8)

print("Enter the Octal Number: ", end="")
onum = input()

obj = fresherearth()
dnum = obj.OctToDec(onum)
print("\nEquivalent Decimal Value =", dnum)

Same Program in Other Languages

Python Online Test


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