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Python Program to Add Two Binary Numbers



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In this article, you will learn and get code to add two binary numbers entered by user using a Python program. Here are the list of programs on binary number addition:

How to Add Two Binary Numbers ?

Here are the rules for binary number addition:

1 + 0 = 1
0 + 1 = 1
0 + 0 = 0
1 + 1 = 10 (0 and carry 1)
1 + 1 + 1 = 11 (1 and carry 1)

For example

  1 1 1 0 1
+ 1 1 1 1 1
-----------
1 1 1 1 0 0

Add Two Binary Numbers Directly

This program find and prints the sum of two given binary numbers in a direct way. Here direct way means, this program is created using int() and bin(), pre-defined function of Python. Let's have a look at the program. I'll explain it later on:

# ----codescracker.com----

print("Enter First Binary Number: ")
nOne = int(input())
print("Enter Second Binary Number: ")
nTwo = int(input())

nOne = str(nOne)
nTwo = str(nTwo)
iSum = int(nOne, 2) + int(nTwo, 2)
bSum = bin(iSum)

print("Result = " + bSum)

Here is its sample run:

python program add binary numbers

Now supply any two binary numbers say 1110 as first and 1111 as second binary number. Here is the sample run with exactly same input:

add two binary numbers python

That is, 1110 + 1111 = 11101 or 0b1110 + 0b1111 = 0b11101.

Note - The int(num, 2) returns a decimal integer equivalent of binary number stored in num. Here 2 is the base of number stored in num

Therefore the following statement:

iSum = int(nOne, 2) + int(nTwo, 2)

converts nOne and nTwo into its decimal integer equivalent and adds them. Its addition result gets initialized to iSum variable. And using bin() method, we've converted the decimal integer value into its equivalent binary number.

Note - The bin() returns binary equivalent string of an integer passed as its argument.

The dry run of above program with user input 1110 and 1111 goes like:

Modified Version of Previous Program

This program is the modified version of previous program with some better looking output:

# ----codescracker.com----

print(end="Enter First Binary Number: ")
nOne = int(input())
print(end="Enter Second Binary Number: ")
nTwo = int(input())

nOne = str(nOne)
nTwo = str(nTwo)
iSum = int(nOne, 2) + int(nTwo, 2)
bSum = bin(iSum)

print("\n" + nOne + " + " + nTwo + " = " + bSum[2:])

Here is its sample run with user input, 111 as first and 111 as second binary number:

binary number addition python

Note - The bSum[2:] is used to print from 2nd index. It is used to skip 0b of bSum. That is 0 is at 0th and b is at 1st index.

Add Two Binary Numbers using User-Defined Code

This program is created with complete user-based code to add two binary numbers entered by user. Because in this program, we've not used any type of pre-defined function:

# ----codescracker.com----

print(end="Enter First Binary Number: ")
nOne = int(input())
print(end="Enter Second Binary Number: ")
nTwo = int(input())

nOne = str(nOne)
nTwo = str(nTwo)
mLen = max(len(nOne), len(nTwo))
nOne = nOne.zfill(mLen)
nTwo = nTwo.zfill(mLen)
addRes = ""
carry = 0

for i in range(mLen - 1, -1, -1):
    re = carry
    if nOne[i] == '1':
        re = re+1
    else:
        re = re+0
    if nTwo[i] == '1':
        re = re+1
    else:
        re = re+0
    if re%2==1:
        addRes = '1' + addRes
    else:
        addRes = '0' + addRes
    if re<2:
        carry = 0
    else:
        carry = 1

if carry!=0:
    addRes = '1' + addRes

print(addRes)

Here is its sample run, 11101 as first and 11111 as second binary number:

add two binary value using python

Note - The zfill() method is used to add zeros (0) at beginning of the string. Its length is specified through its argument.

Note - The max() returns the maximum number from numbers provided as its argument.

Modified Version of Previous Program

This program is again the modified version of previous program. In this program, we've shorten the logical code to create the program that looks little smaller than previous one:

# ----codescracker.com----

print(end="Enter First Binary Number: ")
nOne = int(input())
print(end="Enter Second Binary Number: ")
nTwo = int(input())

nOne = str(nOne)
nTwo = str(nTwo)
mLen = max(len(nOne), len(nTwo))
nOne = nOne.zfill(mLen)
nTwo = nTwo.zfill(mLen)
addRes = ""
carry = 0

for i in range(mLen - 1, -1, -1):
    re = carry
    re += 1 if nOne[i] == '1' else 0
    re += 1 if nTwo[i] == '1' else 0
    addRes = ('1' if re%2==1 else '0') + addRes
    carry = 0 if re<2 else 1

if carry!=0:
    addRes = '1' + addRes

print("\n" + nOne + " + " + nTwo + " = " + addRes)

Here is its sample run with user input 101 as first and 100 as second binary number:

python add binary numbers

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