CODEWITHSUNDEEP
pythonpython-3.xpython-2.7
Amith PV
Amith PV

Reputation: 39

Converting few indexes of the list to hex

I have an integer list arr with five elements/indexes ranging from arr[0] to arr[4]

The last three elements are customer number which ranges from 01 to 250,000. What I need is to convert them to hex in such a way that the array should look like:

For customer 1, arr = [00,00,01,00,00] - cust num is the last three bytes

For customer 2, arr = [00,00,02,00,00] - cust num is the last three bytes

For customer 250,000, arr = [00,00,90,d0,03] - cust num is the last three bytes, 250,000 in hex = 3D090

I know I can use hex() function to individually convert the indexes to hex or can convert the whole array to hex, but how do I convert the value to hex and place it in last three bytes as in the above format?

Upvotes: 1

Views: 171

Answers (2)

gmds
gmds

Reputation: 19885

This will work:

i = 250000

constant = ['00', '00']

result = [constant + [first + second 
                      for first, second in zip(string[::2], string[1::2])][::-1] 
          for string in (f'{i:X}'.zfill(6) for i in range(1, 250001))]
print(result[0])
print(result[-1])

For Python <= 3.5:

i = 250000

constant = ['00', '00']

result = [constant + [first + second 
                      for first, second in zip(string[::2], string[1::2])][::-1] 
          for string in ('{:X}'.format(i).zfill(6) for i in range(1, 250001))]
print(result[0])
print(result[-1])

Output:

['00', '00', '01', '00', '00']
['00', '00', '90', 'D0', '03']

Explanation:

First, we recognise that we can use string formatting to convert each number into a string, which is then padded to length 6 with 0 if needed.

Next, we chunk the string into two-character blocks and reverse it so that it has the representation required.

Lastly, we add two '00' strings to each inner list.

Upvotes: 1

Footer
Footer

Reputation: 139

Might help


import re
def split_hex_rev(number):
    arr = re.findall('..',hex(number).replace('x',''))
    while len(arr)<5:
        arr.append('00')
    arr.reverse()
    return arr

Upvotes: 0

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