Python script to convert hexadecimal to decimal

Question

I've written the python script below to convert hexadecimal to decimal. It seems to work fine, at least as long as the hexadecimal has less then 8 characters .

What did I do wrong ? Tnx !

""" converts hexidecimal to decimal"""
def HextoDec (string):
    ret = 0
    for i in string : 
        hex = "0123456789ABCDEF"
        value= hex.index(i) # 0 to 15  
        index = string.index(i)
        power = (len(string) -(index+1)) #power of 16
        ret += (value*16**power)
    return ret
print(HextoDec("BAABFC7DE"))

Barmar · Accepted Answer · 2018-03-02 23:19:09Z

4

The problem is this line:

index = string.index(i)

index() returns the position of the first match. If the hex number contains any duplicate characters, you'll get the wrong index for all the repeats.

Instead of searching for the index, get it directly when you're iterating:

for index, i in enumerate(string):

answered Mar 2, 2018 at 23:19

Barmar

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lyxal · Accepted Answer · 2018-09-07 02:27:17Z

2

There is a much easier way to convert hexadecimal to decimal without the use of a custom function - just use the built-in int() function like so:

int("BAABFC7DE", base=16) #replace BAABFC7DE with any hex code you want

But if you do want to use a custom function, then Barmar's answer is the best.

edited Sep 7, 2018 at 2:27

answered Mar 2, 2018 at 23:24

lyxal

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2 Comments

Filip Over a year ago

Thanks I know, but since I'm following a course with both an intro to Python and a chapter on hexadecimals, this seemed like a usefull exercise :-)

lyxal Over a year ago

Of course, I was just suggesting a much friendlier way, hence the reason I referred to @Barmar's answer as being the most helpful.

Haaput · Accepted Answer · 2018-03-02 23:30:29Z

1

As Barmar pointed out. The issued is with the line

index = string.index(i)

Which returns first match. Try this:

def HextoDec (string):
    ret = 0
    for i,d in enumerate(string) : 
        hex = "0123456789ABCDEF"
        value= hex.index(d) # 0 to 15
        #index = string.index(i)
        power = (len(string) -(i+1)) #power of 16
        ret += (value*16**power)
    return ret

answered Mar 2, 2018 at 23:30

Haaput

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