Python Slicing | Extract ‘k’ bits from a given position
How to extract ‘k’ bits from a given position ‘p’ in a number?
Examples:
Input : number = 171
k = 5
p = 2
Output : The extracted number is 21
171 is represented as 10101011 in binary,
so, you should get only 10101 i.e. 21.
Input : number = 72
k = 5
p = 1
Output : The extracted number is 8
72 is represented as 1001000 in binary,
so, you should get only 01000 i.e 8.
We have existing solution for this problem please refer Extract ‘k’ bits from a given position in a number link. We can solve this problem quickly in python using slicing. Approach is simple,
- Convert given number into it’s binary using bin() function and remove first two characters ‘0b’ from it, because bin function appends ‘0b’ as prefix in output binary string.
- We need to start extracting k bits from starting position p from right, that means end index of extracted sub-string will be end = (len(binary) – p) and start index will be start = end – k + 1 of original binary string.
- Convert extracted sub-string into decimal again.
# Function to extract ‘k’ bits from a given# position in a number def extractKBits(num,k,p): # convert number into binary first binary = bin(num) # remove first two characters binary = binary[2:] end = len(binary) - p start = end - k + 1 # extract k bit sub-string kBitSubStr = binary[start : end+1] # convert extracted sub-string into decimal again print (int(kBitSubStr,2)) # Driver programif __name__ == "__main__": num = 171 k = 5 p = 2 extractKBits(num,k,p) |
Output:
21
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