Request for help from Python beginner:

I don't want you to do the work for me, just some help to know where my mistakes are and how to correct them.

I am trying to code a program to convert any decimal number into binary. In the case of an infinitely repeating decimal number, the number should terminate at 5 significant digits.

I have nearly all of the code completed, but have encountered a couple of issues.

Here's my code:

``````numint = ""
numfrac = ""
values = ""
binint = ""
binfrac = ""
number = raw_input("Input a number")

values = number.split(".")
integer = int(values[0])

while integer >= 1:
intremainder = integer % 2
integer = integer / 2
intremainder = str(intremainder)
binint = binint + intremainder
binint = binint[::-1]

if "." in number:
fraction = float(values[1]) / (10 ** len(values[1]))
fraction1 = float(fraction) * 2
fraction1 = str(fraction1)
binfrac1 = fraction1[0]
if "1" in binfrac1:
fraction1 = float(fraction1)
fraction1 - 1
binfrac1 = str(binfrac1)

fraction2 = float(fraction1) * 2
fraction2 = str(fraction2)
binfrac2 = fraction2[0]
if "1" in binfrac2:
fraction2 = float(fraction2)
fraction2 - 1
binfrac2 = str(binfrac2)

fraction3 = float(fraction2) * 2
fraction3 = str(fraction3)
binfrac3 = fraction3[0]
if "1" in binfrac3:
fraction3 = float(fraction3)
fraction3 - 1
binfrac3 = str(binfrac3)

fraction4 = float(fraction3) * 2
fraction4 = str(fraction4)
binfrac4 = fraction4[0]
binfrac4 = str(binfrac4)
if "1" in binfrac4:
fraction4 = float(fraction4)
fraction4 - 1
binfrac4 = str(binfrac4)

fraction5 = float(fraction4) * 2
fraction5 = str(fraction5)
binfrac5 = fraction5[0]
binfrac5 = float(binfrac5)
if "1" == binfrac5:
fraction5 = float(fraction5)
fraction5 - 1
binfrac5 = str(binfrac5)

binfrac = binfrac1 + binfrac2 + binfrac3 + binfrac4 + binfrac5

print binint + "." + binfrac``````

Yes, my code isn't particularly elegant. I intend to shorten a lot of it with a while loop, once I get this code working.

My issues are that the if statements that would subtract 1 from the fraction value if the fraction value is greater than 1 don't work.
My second problem is that in the final converted number, I end up with multiple decimal points. I suspect this is a problem with one of my "fraction * 2" lines, but don't know what to do to correct it.

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8 Years
Discussion Span
Last Post by graphpaper
``````fraction1 = float(fraction) * 2
fraction1 = str(fraction1)
binfrac1 = fraction1[0]
if "1" in binfrac1:
fraction1 = float(fraction1)
fraction1 - 1
binfrac1 = str(binfrac1)``````

This logic is flawed. All you're doing is doubling the "fraction" portion of the number, and checking to see if the first number is a 1, at which point you subtract "1" from the number... I haven't done fractional binary conversions in a long time, but can't you just multiply the fraction by ten until it's a whole number, and then push that numberthrough the same logic that you use for the binint portion? Then you'll only need to adjust for decimal at the end.

Granted, my method is rather roundabout, but it's precisely what I wanted to do. Problem is, it doesn't work.

Here's my algorithm:

1. User inputs base 10 number in its entirety
2. Number is split into its integer value and its fractional value
3. The integer value is converted to base 2
• Divide integer value by 2
• Keep remainder
• Divide quotient by 2
• Keep remainder
• Repeat Step 3 and Step 4 until quotient equals 0
• Remainders are concatenated in reverse order they were obtained
4. The fractional value is converted to base 2
• Multiply fractional value by 2
• Record integer value of sum
• Subtract integer value from sum
• Multiply remaining value of sum by 2
• Repeat Step 2, Step 3, and Step 4 until the fraction portion of a sum equals 0 or five integer sum values have been obtained
• Integer sum values are arranged in order they are obtained
• Place a point before the concatenation of the integer sum values
5. The base 2 integer value is concatenated with the base 2 fractional value
6. The converted number is displayed to the screen.

Having looked over my algorithm once again, I may change to fractionX = fractionX -fractionX[0].

I've managed to get it to work.

``````numint = ""
numfrac = ""
values = ""
binint = ""
binfrac1 = ""
binfrac2 = ""
binfrac3 = ""
binfrac4 = ""
binfrac5 = ""
number = raw_input("Input a number")

values = number.split(".")
integer = int(values[0])

while integer >= 1:
intremainder = integer % 2
integer = integer / 2
intremainder = str(intremainder)
binint = binint + intremainder
binint = binint[::-1]

if "." in number:
fraction = float(values[1]) / (10 ** len(values[1]))
fraction1 = float(fraction) + float(fraction)
fraction1 = str(fraction1)
if float(fraction1) >= float(1.0):
binfrac1 = str(1)
fraction1 = float(fraction1) - float(1.0)
elif float(fraction1) < float(1.0):
binfrac1 = str(0)
fraction1 = str(fraction1)

fraction2 = float(fraction1) + float(fraction1)
fraction2 = str(fraction2)
if float(fraction2) >= float(1.0):
binfrac2 = str(1)
fraction2 = float(fraction2) - float(1.0)
elif float(fraction2) < float(1.0):
binfrac2 = str(0)
fraction2 = str(fraction2)

fraction3 = float(fraction2) + float(fraction2)
fraction3 = str(fraction3)
if float(fraction3) >= float(1.0):
binfrac3 = str(1)
fraction3 = float(fraction3) - float(1.0)
elif float(fraction3) < float(1.0):
binfrac3 = str(0)
fraction3 = str(fraction3)

fraction4 = float(fraction3) + float(fraction3)
fraction4 = str(fraction4)
if float(fraction4) >= float(1.0):
binfrac4 = str(1)
fraction4 = float(fraction4) - float(1.0)
elif float(fraction4) < float(1.0):
binfrac4 = str(0)
fraction4 = str(fraction4)

fraction5 = float(fraction4) + float(fraction4)
fraction5 = str(fraction5)
if float(fraction5) >= float(1.0):
binfrac5 = str(1)
fraction5 = float(fraction5) - float(1.0)
elif float(fraction5) < float(1.0):
binfrac5 = str(0)
fraction5 = str(fraction5)

binfrac = binfrac1 + binfrac2 + binfrac3 + binfrac4 + binfrac5

print binint + "." + binfrac``````

It's not particularly elegant, but it gets the job done. Thanks for the help.