How do I reverse each value in a column bit wise for a hex number?

I have a dataframe which has a column called hexa which has hex values like this. They are of dtype object.

               hexa
0  00802259AA8D6204
1  00802259AA7F4504
2  00802259AA8D5A04

I would like to remove the first and last bits and reverse the values bitwise as follows:

         hexa-rev
0  628DAA592280
1  457FAA592280
2  5A8DAA592280

Please help

Solution

I'll show you the complete solution up here and then explain its parts below:

def reverse_bits(bits):
    trimmed_bits = bits[2:-2]
    list_of_bits = [i+j for i, j in zip(trimmed_bits[::2], trimmed_bits[1::2])]
    reversed_bits = [list_of_bits[-i] for i in range(1,len(list_of_bits)+1)]
    return ''.join(reversed_bits)

df['hexa-rev'] = df['hexa'].apply(lambda x: reverse_bits(x))

There are possibly a couple ways of doing it, but this way should solve your problem. The general strategy will be defining a function and then using the apply() method to apply it to all values in the column. It should look something like this:

df['hexa-rev'] = df['hexa'].apply(lambda x: reverse_bits(x))

Now we need to define the function we're going to apply to it. Breaking it down into its parts, we strip the first and last bit by indexing. Because of how negative indexes work, this will eliminate the first and last bit, regardless of the size. Your result is a list of characters that we will join together after processing.

def reverse_bits(bits):
    trimmed_bits = bits[2:-2]

The second line iterates through the list of characters, matches the first and second character of each bit together, and then concatenates them into a single string representing the bit.

def reverse_bits(bits):
    trimmed_bits = bits[2:-2]
    list_of_bits = [i+j for i, j in zip(trimmed_bits[::2], trimmed_bits[1::2])]

The second to last line returns the list you just made in reverse order. Lastly, the function returns a single string of bits.

def reverse_bits(bits):
    trimmed_bits = bits[2:-2]
    list_of_bits = [i+j for i, j in zip(trimmed_bits[::2], trimmed_bits[1::2])]
    reversed_bits = [list_of_bits[-i] for i in range(1,len(list_of_bits)+1)]
    return ''.join(reversed_bits)

I explained it in reverse order, but you want to define this function that you want applied to your column, and then use the apply() function to make it happen.