How to convert decimal to binary list in python [duplicate]

Question

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

how do I convert a decimal number into a binary list.

For example, how do I change 8 into [1,0,0,0]

I tried this: binary = 0 while num != 0: bit = num % 2 binary = bit +(10* binary) num = num / 2 binary=[binary] return binary but it doesn't give me commas between the numbers, and it doesn't always add the zeros. — booboboobobob
– booboboobobob, Commented Nov 26, 2012 at 2:39
What have you tried? You might want to look at the python docs for the function bin. — Yuushi
– Yuushi, Commented Nov 26, 2012 at 2:39

mgilson · Accepted Answer · 2012-11-26 02:39:32Z

32

You can probably use the builtin bin function:

bin(8) #'0b1000'

to get the list:

[int(x) for x in bin(8)[2:]]

Although it seems like there's probably a better way...

answered Nov 26, 2012 at 2:39

mgilson

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1 Comment

slacy Over a year ago

Relying on string representation details and going from an integer to a string and then to a list seems....suboptimal.

Sean Redmond · Accepted Answer · 2012-11-26 02:55:56Z

22

Try this:

>>> list('{0:0b}'.format(8))
['1', '0', '0', '0']

Edit -- Ooops, you wanted integers:

>>> [int(x) for x in list('{0:0b}'.format(8))]
[1, 0, 0, 0]

Another edit --

mgilson's version is a little bit faster:

$ python -m timeit "[int(x) for x in list('{0:0b}'.format(8))]"
100000 loops, best of 3: 5.37 usec per loop
$ python -m timeit "[int(x) for x in bin(8)[2:]]"
100000 loops, best of 3: 4.26 usec per loop

edited Nov 26, 2012 at 2:55

answered Nov 26, 2012 at 2:46

Sean Redmond

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Comments

Alexey Feldgendler · Accepted Answer · 2012-11-26 02:46:07Z

7

In the spirit of your original attempt:

binary = []
while num != 0:
    bit = num % 2
    binary.insert(0, bit)
    num = num / 2

answered Nov 26, 2012 at 2:46

Alexey Feldgendler

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1 Comment

Tim Over a year ago

Would be better to .append() the bits then .reverse() the list at the end rather than inserting at the start of the list.

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