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Binary to decimal and vice-versa in python
• Difficulty Level : Easy
• Last Updated : 11 Sep, 2018

Write Python code for converting a decimal number to it’s binary equivalent and vice-versa.

Example:

```From decimal to binary
Input : 8
Output : 1 0 0 0

From binary to decimal
Input : 100
Output : 4
```

## Recommended: Please try your approach on {IDE} first, before moving on to the solution.

Decimal to binary

```Keep calling conversion function with n/2  till n > 1,
later perform n % 1 to get MSB of converted binary number.
Example :- 7
1). 7/2 = Quotient = 3(grater than 1), Remainder = 1.
2). 3/2 = Quotient = 1(not grater than 1), Remainder = 1.
3). 1%2 = Remainder = 1.
Therefore, answer is 111.
```
 `# Function to print binary number for the ``# input decimal using recursion ``def` `decimalToBinary(n): `` ` `    ``if``(n > ``1``): ``        ``# divide with integral result ``        ``# (discard remainder) ``        ``decimalToBinary(n``/``/``2``) `` ` `     ` `    ``print``(n``%``2``, end``=``' '``)``     ` `     ` ` ` `# Driver code ``if` `__name__ ``=``=` `'__main__'``: ``    ``decimalToBinary(``8``) ``    ``print``(``"\n"``)``    ``decimalToBinary(``18``) ``    ``print``(``"\n"``)``    ``decimalToBinary(``7``) ``    ``print``(``"\n"``)`

Output:

```1 0 0 0
1 0 0 1 0
1 1 1
```

Decimal to binary using bin():

 `# Function to convert Decimal number``# to Binary number`` ` `def` `decimalToBinary(n):``    ``return` `bin``(n).replace(``"0b"``,"")`` ` `# Driver code``if` `__name__ ``=``=` `'__main__'``:``    ``print``(decimalToBinary(``8``))``    ``print``(decimalToBinary(``18``))``    ``print``(decimalToBinary(``7``))`

Output:

```1000
10010
111
```

Binary to decimal

```Example -: 1011
1). Take modulo of given binary number with 10.
(1011 % 10 = 1)
2). Multiply rem with 2 raised to the power
it's position from right end.
(1 * 2^0)
Note that we start counting position with 0.
3). Add result with previously generated result.
decimal = decimal + (1 * 2^0)
4). Update binary number by dividing it by 10.
(1011 / 10 = 101)
5). Keep repeating upper steps till binary > 0.

Final Conversion -: (1 * 2^3) + (0 * 2^2) +
(1 * 2^1) + (1 * 2^0) = 11

```
 `# Function calculates the decimal equivalent ``# to given binary number`` ` `def` `binaryToDecimal(binary):``     ` `    ``binary1 ``=` `binary``    ``decimal, i, n ``=` `0``, ``0``, ``0``    ``while``(binary !``=` `0``):``        ``dec ``=` `binary ``%` `10``        ``decimal ``=` `decimal ``+` `dec ``*` `pow``(``2``, i)``        ``binary ``=` `binary``/``/``10``        ``i ``+``=` `1``    ``print``(decimal)    ``     ` ` ` `# Driver code``if` `__name__ ``=``=` `'__main__'``:``    ``binaryToDecimal(``100``)``    ``binaryToDecimal(``101``)``    ``binaryToDecimal(``1001``)`

Output:

```4
5
9
```

Binary to decimal using int():

 `# Function to convert Binary number``# to Decimal number`` ` `def` `binaryToDecimal(n):``    ``return` `int``(n,``2``)`` ` ` ` `# Driver code``if` `__name__ ``=``=` `'__main__'``:``    ``print``(binaryToDecimal(``'100'``))``    ``print``(binaryToDecimal(``'101'``))``    ``print``(binaryToDecimal(``'1001'``))`

Output:

```4
5
9
```

This article is contributed by Pushpanjali Chauhan. If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.

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