need help converting decimal numbers to binary and vice versa

[victory2006]

like we have an integer value of : 9
and i need to convert it to binary numbers

and vice versa, thanks!

[victory2006]

oh wait, how about this..
a list:
[0, 0, 1, 1]

i need to make it so that it will read that as 0011, so that i will be a binary number.

so i need [0, 0, 1, 1] to equal 0011

THEN i need help to convert 0011 into base 10...THANKS

[victory2006]

well i did this,

for a in patrow2:
        print "      "
        for b in a:
             print b,

OUTPUT:
**
1 0 0
1 1 0
1 1 0
**
patrow2 is the list of lists , which in this case is [[1, 0, 0], [1, 1, 0], [1, 1, 0]]

but how do u get rid of the spaces in between the numbers?

[bvdet]

well i did this,

for a in patrow2:
        print "      "
        for b in a:
             print b,

OUTPUT:
**
1 0 0
1 1 0
1 1 0
**
patrow2 is the list of lists , which in this case is [[1, 0, 0], [1, 1, 0], [1, 1, 0]]

but how do u get rid of the spaces in between the numbers?

Following are two ways:

>>> patrow2 = [[1, 0, 0], [1, 1, 0], [1, 1, 0]]
>>> for item in patrow2:
... 	print ''.join([str(i) for i in item])
... 	
100
110
110
>>> for item in patrow2:
... 	print '%d%d%d' % tuple(item)
... 	
100
110
110
>>>

To convert from binary to decimal, use built-in function int().

>>> int('011', 2)
3
>>>

[MorseCode]

Something I whipped up once to convert decimal to binary:

def dec2biprog():
    empt = ""
    def dec2bi(x):
        y = empt
        z = 0
        power = range(1, 51)
        power.reverse()
        for i in power:
            power[z] = 2**power[z]
            z = z + 1
        power.append(1)
        for i in power:
            if x >= i:
                x = x - i
                y = y + "1"
            else:
                y = y + "0"
        a = 0
        for i in y:
            if i == "0":
                a = a + 1
            elif i == "1":
                return y[a:100]

And the UI:

    print """Welcome to D2B, the program that converts your decimal
    (or base 10) numbers into binary (or base 2) numbers.
    """
    erone = 0
    while True:
        inp = raw_input("Please enter your number here: ")
        print empt
        try:
            if inp == "0" or int(inp) < 0:
                print "Please pick a number greater than 0!"
                erone = 1
        except ValueError:
            print "Pick a number!"
            erone = 1
        if erone != 1:
            if int(inp) > 1125899906842624:
                print "Pick a number less than 1,125,899,906,842,625, please."
                erone = 1
        if erone != 1:
            print "Your number, " + str(inp) + ", is " + dec2bi(int(inp)) + " in binary!"
        else:
            erone = 0
        print empt
        ertest = 0
dec2biprog()

[bvdet]

MorseCode,

Thank you for sharing your code with us. You can streamline your code a bit by using range() with a negative step in a list comprehension.
Original code:

        z = 0
        power = range(1, 51)
        power.reverse()
        for i in power:
            power[z] = 2**power[z]
            z = z + 1
        power.append(1)

Recommended code:

        power = [2**i for i in range(50, -1, -1)]

You are removing the leftmost "0"s with a for loop. You can use string method lstrip() for this.
Original code:

    
        a = 0
        for i in y:
            if i == "0":
                a = a + 1
            elif i == "1":
                return y[a:100]

Recommended code:

        return y.lstrip('0')

There is nothing wrong with string concatenation. I prefer string formatting for efficiency and readability.
Original code:

print "Your number, " + str(inp) + ", is " + dec2bi(int(inp)) + " in binary!"

Recommended code:

print "Your number, %s, is %s in binary" % (inp, dec2bi(int(inp))

[MorseCode]

Thanks for the help, bv, you taught me (a fairly new newb) a few things I didn't know.
Namely, everything you showed me in your post. Lol.

[bvdet]

You're welcome MorseCode. Following is a function that will convert a decimal number to any base between and including 2-36. It uses built-in function divmod() and recursion.

def convDecToBase(num, base, dd=False):
    ''' Convert a decimal integer to a base between and including 2-36.'''
    if not 2 <= base <= 36:
        raise ValueError, 'The base number must be between 2 and 36.'
    if not dd:
        dd = dict(zip(range(36), list(string.digits+string.ascii_lowercase)))
    if num == 0: return ''
    num, rem = divmod(num, base)
    return convDecToBase(num, base, dd)+dd[rem]