Converting raised position to binary

I am working on going from o-string binary to Unicode, part of this process requires converting Raised Position to Binary. I can't seem to be able to get it done. The doc test will explain what needs to be performed.

I have provided my code below but it is nowhere close to getting the correct answer.

def raisedpos_to_binary(s): ''' (str) -> str Convert a string representing a braille character in raised-position representation into the binary representation. TODO: For students to complete.

>>> raisedpos_to_binary('')
'00000000'
>>> raisedpos_to_binary('142536')
'11111100'
>>> raisedpos_to_binary('14253678')
'11111111'
>>> raisedpos_to_binary('123')
'11100000'
>>> raisedpos_to_binary('125')
'11001000'
'''

res = ''
lowest_value = '00000000'
for i, c in enumerate(s):
    if c == i:
        lowest_value = lowest_value.replace('0', '1')
return lowest_value

Looks like you can create a set (converted to integers) of the single digits and then produce '1' or '0' iterating over a range of 1..8, eg:

def raisedpos_to_binary(digits):
    raised = {int(digit) for digit in digits}
    return ''.join('1' if n in raised else '0' for n in range(1, 9))

Tests:

for test in ['', '142536', '14253678', '123', '125']:
    print(test, '->', raised_pos_to_binary(test))

Gives you:

 -> 00000000
142536 -> 11111100
14253678 -> 11111111
123 -> 11100000
125 -> 11001000

So in full, your module should contain:

def raisedpos_to_binary(digits):
    """
    >>> raisedpos_to_binary('')
    '00000000'
    >>> raisedpos_to_binary('142536')
    '11111100'
    >>> raisedpos_to_binary('14253678')
    '11111111'
    >>> raisedpos_to_binary('123')
    '11100000'
    >>> raisedpos_to_binary('125')
    '11001000'
    """

    raised = {int(digit) for digit in digits}
    return ''.join('1' if n in raised else '0' for n in range(1, 9))


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

Then run your script using:

python your_script.py -v