On 20/04/2015 21:47, Ben Finney wrote:
Jim Mooney <cybervigila...@gmail.com> writes:
I can't seem to get my head around this 'simple' book example of
binary-to-decimal conversion, which goes from left to right:
B = '11011101'
I = 0
while B:
I = I * 2 + int(B[0])
B = B[1:]
print(I)
221
That is, IMO, a needlessly confusing way to write that code.
Whoever wrote it is clearly pleased with how clever it is; but
cleverness is almost always a property of *bad* code because it's
difficult to understand at a glance. That's the case here.
One significant problem with the code as written is that it uses a
‘while’ loop and mutates the list, where there's no point; it should
just iterate over items *from* the list without changing it.
Another significant problem is that it uses moronically-short,
completely unexpressive names. This is Python not FORTRAN.
Try this::
binary_text = '11011101'
result = 0
for binary_digit in binary_text:
# Accumulate powers of 2 for each digit.
result = result * 2 + int(binary_digit)
print(result)
Both methods work but I just can't see how the first one does. Am I
missing something obvious here?
No, you were missing something needlessly obscured by the badly-written
code. Which book is this? I will be sure never to recommend it.
Hope that helps.
I agree entirely so a big +1 from me.
--
My fellow Pythonistas, ask not what our language can do for you, ask
what you can do for our language.
Mark Lawrence
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