 # Python: bin() function

## bin() function

The bin() function is used to convert an integer number to a binary string. The result is a valid Python expression.

Syntax:

```bin(x)
``` Version:

(Python 3.2.5)

Note: If x is not a Python int object, it has to define an __index__() method that returns an integer.

Return value:

integer.

Example: Python bin() function - Convert integer to binary

``````x = 10
print("Original number: ",x)
y = bin(x)
print("Binary string:")
print (y)
x = -10
print("\nOriginal number: ",x)
y = bin(x)
print("Binary string:")
print (y)
``````

Output:

```Original number:  10
Binary string:
0b1010
Original number:  -10
Binary string:
-0b1010```

Example: Python bin() function - Convert integer to binary without sign prefix

``````x = 10
print("Original number: ",x)
print(x)
print("Binary string:")
print(bin(x)[2:].zfill(8))
x = -10
print("\nOriginal number: ",x)
print(x)
print("Binary string:")
print(bin(x)[3:].zfill(8))
``````

Output:

```Original number:  10
10
Binary string:
00001010

Original number:  -10
-10
Binary string:
00001010```

Example: Convert an integer to binary without using bin() function

``````def dec_to_bin(n):
binary = ""
x = 0
while n > 0 and x<=8:
s1 = str(int(n%2))
binary = binary + s1
n /= 2
x = x + 1
result = binary[::-1]
return result
print(dec_to_bin(10))
print(dec_to_bin(8))
print(dec_to_bin(110))
``````

Output:

```000001010
000001000
001101110```

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## Python: Tips of the Day

How do I check if a list is empty?

For example, if passed the following:

```a = []
if not a:
print("List is empty")
```

Ref: https://bit.ly/2A4JXx9