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

all numbers are stored in binary. if you want a textual representation of a given number in binary, use bin(i)

>>> bin(10)
'0b1010'
>>> 0b1010
10

To convert from binary to decimal, just do:

int(binary_string, 2)  # The 2 is the base argument from which we convert.

Demo:

>>> int('0b10110', 2)
22

Note- There are many issues with the code you are using to convert decimal to binary. If you are insistent on not using a built-in function for that purpose, you may be interested by this post:

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

Although personally if I were to want to avoid the bin() function, I would do something like:

"{0:#b}".format(an_integer)

Demo:

>>> "{0:#b}".format(22)
'0b10110'

This is much more Pythonic than your current code.

• You can remove half of you code.
  You need the variables exp, total and decimal. The rest are just noise.

• You should remove all the int(decimal)s, decimal is only ever subtracted from, and so it's not going to become a float. And so these are not needed.

1. You can remove all the code in if 2 ** exp == int(decimal):, instead just use exp as you do zeros.

2. You should split your while loop so that it only does one thing at a time. You want an int log and then a while loop that converts the input to binary.

3. You can replace while zeros > 0: with Pythons way to duplicate strings. 0 * zeros.

4. You should make this a function.

This leads to code like:

def binary(number): # 4
    output = ''
    if number < 0:
        output = '-'
        number = -number

    exp = 1
    while 2 ** exp <= number: # 2
        exp += 1

    while number > 0:
        exp -= 1
        if 2 ** exp <= number:
            number -= 2 ** exp
            output += '1'
        else:
            output += '0'

    return output + '0' * exp # 1, 3


number = int(input("Enter a whole number: "))
print('Binary: ' + binary(number))