Decimal to hexadecimal conversion

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I need to make an algorithm in python to make a converter from decimal to hexadecimal. But I can not use ifs nor ready functions, like hex (). I did, but when I was printing the value in hex, I used print ("% X"% h) to print the letters without using the if, but I realized that this converts any number into hexadecimal, but that would be a ready function and not This is what I want. Is there a way to do this? My code: 

n = int(input())
r = []

while n > 0:
    r.append(n % 16)
    n = n // 16

for i in range(len(r)-1,-1,-1):
    print("%X"%r[i],end="")
    
asked by anonymous 30.06.2017 / 22:40

2 answers

1

You can do this: 

hex = [0,1,2,3,4,5,6,7,8,9,"A","B","C","D","E","F"]
n = int(input("Digite um núemro inteiro: "))
r = []
while n > 0:
    r.append(hex[(n % 16)])
    n = n // 16
for i in range(len(r)-1,-1,-1):
    print(r[i],end="")

See Ideone

    
01.07.2017 / 04:44
0

In this example I used doctest to validate the results. 

def int2hex(n):
    '''
    :param n: int
    :return: str
    >>> int2hex(10)
    'A'
    >>> int2hex(15)
    'F'
    >>> int2hex(32)
    '20'
    >>> int2hex(255)
    'FF'
    >>> int2hex(65535)
    'FFFF'
    '''

    x16 = '0 1 2 3 4 5 6 7 8 9 a b c d e f'.upper().split()
    result = []
    while n > 0:
        result.append(x16[(n % 16)])
        n = n // 16
    result.reverse()
    return ''.join(result)

if __name__ == '__main__':
    import doctest
    doctest.testmod()

    print(int2hex(64202))

The excerpt: 

>>> int2hex(10)
'A'

Refer to doctest calls, where the first line is the method call and the second is the expected result.

On line: 

x16 = '0 1 2 3 4 5 6 7 8 9 a b c d e f'.upper().split()

I create a high-box list with hexadecimal values.

In the excerpt: 

while n > 0:
    result.append(x16[(n % 16)])
    n = n // 16

I decompose base number 10 to base 16, however it is stored in reverse.

On line: 

result.reverse()

I inverted the values stored in the list.

and finally in the line: 

return ''.join(result)

I convert the list to string and return it as a response.

How to run the excerpt: 

print(int2hex(64202))

results in 'FACA'

If it is necessary to enter the values in the format string, you can add a casting and also treatment of exceptions.

Complete example: 

def int2hex(n):
    '''
    :param n: int
    :return: str
    >>> int2hex(10)
    'A'
    >>> int2hex(15)
    'F'
    >>> int2hex(32)
    '20'
    >>> int2hex(255)
    'FF'
    >>> int2hex(65535)
    'FFFF'
    '''

    x16 = '0 1 2 3 4 5 6 7 8 9 a b c d e f'.upper().split()
    result = []
    try:
        n = int(n)

        while n > 0:
            result.append(x16[(n % 16)])
            n = n // 16
        result.reverse()
    except ValueError as e:
        return ('Erro: %s' %e)
    except:
        raise
    else:
        return ''.join(result)

if __name__ == '__main__':
    import doctest
    doctest.testmod()


    print(int2hex(64202))
    print(int2hex('20'))
    print(int2hex('a'))
    print(int2hex('15'))
    
10.07.2017 / 17:26
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