Binary conversion returning decimal value

Question

I am trying to display all the binary numbers which are divisible by 5 and I am able to successfully show them. But the output is in decimal format even though I have converted them to base 2 (binary).

My code -

user_input = raw_input("Enter three numbers separated by commas: ")
input_list = user_input.split(',')
decimal_list=[]
binary_list=[]
for i in input_list:
     decimal_list.append(int(i,2))
print decimal_list
for x in decimal_list:
    if x%5==0:
        binary_list.append(int(str(x),10))
print binary_list

My input

0000,0001,0010,0011,0100,0101,0110,0111,1000

Output -

[0, 1, 2, 3, 4, 5, 6, 7, 8]
[0, 5]

Why do I get [0,5] instead of [0000,0101] ? I did convert them back to binary using (int(str(x),10))

because python representation of a list of integers is done in base 10. — Jean-François Fabre, Feb 23 '18 at 13:52
@AkshayNevrekar How do i convert it to binary then ? Or how do I represent the list in binary format ? — Pirate X, Feb 23 '18 at 13:55

score 1 · Answer 1 · answered Feb 23 '18 at 13:58

When you have a list of integers and you use print on it, you're implicitly calling list.__repr__() method on it.

This method creates a string with integer numbers in base 10 separated with commas and wrapped with brackets.

If you want to print in binary, you could create a special list object (inheriting from list) and change the way it's represented:

class BinaryList(list):
    def __repr__(self):
        return "[{}]".format(",".join("0b{:04b}".format(x) for x in self))

user_input = "0000,0001,0010,0011,0100,0101,0110,0111,1000"
input_list = user_input.split(',')
decimal_list=[]
binary_list=BinaryList()   # here we're using our special class
for i in input_list:
     decimal_list.append(int(i,2))
print(decimal_list)
for x in decimal_list:
    if x%5==0:
        binary_list.append(int(str(x),10))
print(binary_list)

that prints:

[0, 1, 2, 3, 4, 5, 6, 7, 8]
[0b0000,0b0101]

This list is specialized: if you enter strings in it, the __repr__ method will fail because of incompatible format. Also note that I have added the 0b prefix in the representation to be able to copy/paste the result & keep the proper values, and avoid mixing it up with decimals.

Binary conversion returning decimal value

1 Answers1