How to assign letters to numbers while converting hexadecimal base to decimal python 3?

Question

I am writing a code that converts a user inputted hexadecimal (base 16) number to base 10, but I can't use any built-in python functions, so it looks like this:

def base16TO10(base16):
    value = base16
    hexadecimal = sum(int(c) * (16 ** i) for i, c in    enumerate(value[::-1]))
    print("Base 16 number:" , base16 , "is base 10 number:" , hexadecimal ,"\n")

I need to make it so that if the letters A, B, C, D, E, or F are inputted as part of a base 16 number, the function will recognize them as 10,11,12,13,14, and 15, respectively, and will convert the number to base 10. Thanks!

If you are using `int(c)`, can you not just use `int(base16, 16)`? — James, Oct 12 '17 at 02:57
If you want this to be super manual, you could use a dictionary to convert chars to ints. — combinatorist, Oct 12 '17 at 03:30
Possible duplicate of [Convert hex string to int in Python](https://stackoverflow.com/questions/209513/convert-hex-string-to-int-in-python) — Anton vBR, Nov 28 '17 at 20:53

score 0 · Answer 1 · answered Nov 28 '17 at 20:40

This seems a lot like answering a homework problem... but ok, here goes. My first solution to the problem is something like this:

def base16TO10(base16):
    conversion_list = '0123456789ABCDEF'
    hexadecimal = sum(conversion_list.index(c) * (16 ** i) for i, c in enumerate(base16[::-1]))
    print("Base 16 number:" , base16 , "is base 10 number:" , hexadecimal ,"\n")

However, we're still using a bunch of built in Python functions. We use list.index, sum, and enumerate. So, cutting the use of those functions out and ignoring that the dictionary subscript operator is an implicit call to dictionary. __getitem__, I have:

def base16TO10(base16):
    conversion_dict = {'0':0, '1':1, '2':2, '3':3, 
                       '4':4, '5':5, '6':6, '7':7,
                       '8':8, '9':9, 'A':10, 'B':11,
                       'C':12, 'D':13, 'E':14, 'F':15}
    digit=0
    hexadecimal=0
    for c in base16[::-1]:
        hexadecimal += conversion_dict[c] * (16 ** digit)
        digit += 1
    print("Base 16 number:" , base16 , "is base 10 number:" , hexadecimal ,"\n")

How to assign letters to numbers while converting hexadecimal base to decimal python 3?

1 Answers1