["python","hex","padding","built-in"]
Decorating Hex function to pad zeros

I wrote this simple function: def padded_hex(i, l): given_int = i given_len = l hex_result = hex(given_int)[2:] # remove '0x' from beginning of str num_hex_chars = len(hex_result) extra_zeros = '0' * (given_len - num_hex_chars) # may not get used.. return ('0x' + hex_result if num_hex_chars == given_len else '?' * given_len if num_hex_chars > given_len else '0x' + extra_zeros + hex_result if num_hex_chars < given_len else None) Examples: padded_hex(42,4) # result '0x002a' hex(15) # result '0xf' padded_hex(15,1) # result '0xf' Whilst this is clear enough for me and fits my use case (a simple test tool for a simple printer) I can't help thinking there's a lot of room for improvement and this could be squashed down to something very concise. What other approaches are there to this problem?
Starting with Python 3.6, you can: >>> value = 42 >>> padding = 6 >>> f"{value:#0{padding}x}" '0x002a' Note the padding includes the 0x. If you don't want that you can do >>> f"0x{value:0{padding}x}" '0x00002a' for older python versions use the .format() string method: >>> "{0:#0{1}x}".format(42,6) '0x002a' Explanation: { # Format identifier 0: # first parameter # # use "0x" prefix 0 # fill with zeroes {1} # to a length of n characters (including 0x), defined by the second parameter x # hexadecimal number, using lowercase letters for a-f } # End of format identifier If you want the letter hex digits uppercase but the prefix with a lowercase 'x', you'll need a slight workaround: >>> '0x{0:0{1}X}'.format(42,4) '0x002A'