Convert an integer to binary without using the built-in bin function

Question

This function receives as a parameter an integer and should return a list representing the same value expressed in binary as a list of bits, where the first element in the l

Answer 1

def trans(x):
    if x == 0: return [0]
    bit = []
    while x:
        bit.append(x % 2)
        x >>= 1
    return bit[::-1]

Answer 2

Padded with length

In most cases you want your binary number to be a specific length. For example you want 1 to be 8 binary digits long [0,0,0,0,0,0,0,1]. I use this myself:

def convert_to_binary(num, length=8):
    binary_string_list = list(format(num, '0{}b'.format(length)))
    return [int(digit) for digit in binary_string_list]

Answer 3

# dec2bin.py
# FB - 201012057
import math

def dec2bin(f):
    if f >= 1:
        g = int(math.log(f, 2))
    else:
        g = -1
    h = g + 1
    ig = math.pow(2, g)
    st = ""    
    while f > 0 or ig >= 1: 
        if f < 1:
            if len(st[h:]) >= 10: # 10 fractional digits max
                   break
        if f >= ig:
            st += "1"
            f -= ig
        else:
            st += "0"
        ig /= 2
    st = st[:h] + "." + st[h:]
    return st

# MAIN
while True:
    f = float(raw_input("Enter decimal number >0: "))
    if f <= 0: break
    print "Binary #: ", dec2bin(f)
    print "bin(int(f)): ", bin(int(f)) # for comparison

Answer 4

You can first use the format function to get a binary string like your current function. For e.g the following snippet creates a binary string of 8 bits corresponding to integer 58.

>>>u = format(58, "08b")
'00111010'

Now iterate the string to convert each bit to an int to get your desired list of bits encoded as integers.

>>>[int(d) for d in u]
[0, 0, 1, 1, 1, 0, 1, 0]

Answer 5

This will do it. No sense in rolling your own function if there's a builtin.

def binary(x):
    return [int(i) for i in bin(x)[2:]]

The bin() function converts to a string in binary. Strip of the 0b and you're set.

Answer 6

Converting decimal to binary is a matter of how you are going to use the % and //

def getbin(num):
    if (num==0):
        k=[0] 
        return k 
    else:
        s = []
        while(num):
            s.append(num%2)
            num=num//2
        return s