The part that converts the binary is int. From the documentation:

if base is given, then x must be a string, bytes, or bytearray instance representing an integer literal in radix base.

This means that int accepts a string representing an integer, that you tell it the base of. E.g. here we give it "11", and tell it this is in base 2, so it returns the integer 3 in decimal.

>>> int("11", 2)
3

Note that when supplying the base argument, you have to give a string:

>>> int(11, 2)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: int() can't convert non-string with explicit base

And you can't use digits that are invalid in the given base:

>>> int("21", 2)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: invalid literal for int() with base 2: '21'

Just take your print() instruction out of your for loop, otherwise it will print every step to your answer.

You can use int and set the base to 2 (for binary):

>>> binary = raw_input('enter a number: ')
enter a number: 11001
>>> int(binary, 2)
25
>>>

However, if you cannot use int like that, then you could always do this:

binary = raw_input('enter a number: ')
decimal = 0
for digit in binary:
    decimal = decimal*2 + int(digit)
print decimal

Below is a demonstration:

>>> binary = raw_input('enter a number: ')
enter a number: 11001
>>> decimal = 0
>>> for digit in binary:
...     decimal = decimal*2 + int(digit)
...
>>> print decimal
25
>>>

To get precisely 8 bits, use string formatting:

A demo:

>>> '{0:08b}'.format(22)
'00010110'

You can simply try format

l =[101, 1101, 11001]

c = "{:08d}".format
print([c(item) for item in l])

output #

['00000101', '00001101', '00011001']

As a function

def bit8(input):
    c = "{:08d}".format
    ou=([c(item) for item in input])

    return ou

Driver code

print(bit8(l))

zfill also works

l =[101, 1101, 11001]


def bit8(input):
    ou2=[str(i).zfill(8) for i in input]
    return ou2

Driver code #

print(bit8(l))

output for zfill method #

['00000101', '00001101', '00011001']

You do have to print the value:

>>> print(bin(160))  # This version gives the 0b prefix for binary numbers.
0b10100000
>>> print(format(160,'08b'))  # This specifies leading 0, 8 digits, binary.
10100000
>>> print('{:08b}'.format(160)) # Another way to format.
10100000
>>> print(f'{160:08b}')  # Python 3.6+ new f-string format.
10100000