How do I convert an integer into a binary string in Python?
37 → '100101'
How do I convert an integer into a binary string in Python?
37 → '100101'
Python's string format method can take a format spec.
>>> "{0:b}".format(37)
'100101'
str.format()
just to format one value is overkill. Go straight to the format()
function: format(n, 'b')
. There is no need to parse out the placeholder and match it to an argument, go straight for the value formatting operation itself. Only use str.format()
if you need to place the formatted result in a longer string (e.g. use it as a template). –
Lacy 0
to the formatting string: format(10, '016b')
formats to 16 digits with leading zeros. –
Lacy 0
in "{0:b}"
can be dropped no? I mean, in the case where only one number is being formatted, it is correct to put "{:b}"
, isn't it? –
Nor "{:08b}".format(37)
–
Aam 0b10100101
. But with an unsigned integer, that value would be 165. So it is not this simple. The answer should reflect this. –
Hrutkay If you're looking for bin()
as an equivalent to hex()
, it was added in python 2.6.
Example:
>>> bin(10)
'0b1010'
str(bin(i))[2:]
(0.369s for 1000000ops) than "{0:b}".format(i)
(0.721s for 1000000ops) –
Condemnation str.format()
is the wrong tool anyway, you would use format(i, 'b')
instead. Take into account that that also gives you padding and alignment options though; format(i, '016b')
to format to a 16-bit zero-padded binary number. To do the same with bin()
you'd have to add a str.zfill()
call: bin(i)[2:].zfill(16)
(no need to call str()
!). format()
's readability and flexibility (dynamic formatting is much harder with bin()
) are great tradeoffs, don't optimise for performance unless you have to, until then optimise for maintainability. –
Lacy f"{37:b}"
. –
Leekgreen Python actually does have something already built in for this, the ability to do operations such as '{0:b}'.format(42)
, which will give you the bit pattern (in a string) for 42
, or 101010
.
For a more general philosophy, no language or library will give its user base everything that they desire. If you're working in an environment that doesn't provide exactly what you need, you should be collecting snippets of code as you develop to ensure you never have to write the same thing twice. Such as, for example, the pseudo-code:
define intToBinString, receiving intVal:
if intVal is equal to zero:
return "0"
set strVal to ""
while intVal is greater than zero:
if intVal is odd:
prefix "1" to strVal
else:
prefix "0" to strVal
divide intVal by two, rounding down
return strVal
which will construct your binary string based on the decimal value. Just keep in mind that's a generic bit of pseudo-code which may not be the most efficient way of doing it though, with the iterations you seem to be proposing, it won't make much difference. It's really just meant as a guideline on how it could be done.
The general idea is to use code from (in order of preference):
s = "1" + s
and s = "0" + s
lines. Each makes an unnecessary copy of s. You should reverse the string just before you return it instead. –
Cerebration '{0:b}'.format(42)
, the slow method was simply an example of how to do it generically, which may or may not be O(n^2) depending on the actual language used. It only looks like Python since Python is an ideal pseudo-code language so I'll change that to make it clear. –
Indeciduous s = "1" + s
wasn't O(N) when s
is a string type. Maybe a language where all strings are stored backwards or each char is a node in a linked list? For any typical language a string is basically an array of chars. In that case prefixing a string requires that a copy is made, how else are you going to put the character before the other characters? –
Cerebration If you want a textual representation without the 0b-prefix, you could use this:
get_bin = lambda x: format(x, 'b')
print(get_bin(3))
>>> '11'
print(get_bin(-3))
>>> '-11'
When you want a n-bit representation:
get_bin = lambda x, n: format(x, 'b').zfill(n)
>>> get_bin(12, 32)
'00000000000000000000000000001100'
>>> get_bin(-12, 32)
'-00000000000000000000000000001100'
Alternatively, if you prefer having a function:
def get_bin(x, n=0):
"""
Get the binary representation of x.
Parameters
----------
x : int
n : int
Minimum number of digits. If x needs less digits in binary, the rest
is filled with zeros.
Returns
-------
str
"""
return format(x, 'b').zfill(n)
format(integer, 'b')
. bin()
is a debugging tool, specifically aimed at producing the Python binary integer literal syntax, format()
is meant to produce specific formats. –
Lacy bin()
is a debugging tool aimed at producing the Python binary integer literal syntax? I couldn't find that in the documentation. –
Litmus oct()
and hex()
. –
Lacy str.zfill()
you could use str.format()
or format()
with a dynamic second argument: '{0:0{1}b}'.format(x, n)
or format(b, '0{}b'.format(n))
. –
Lacy zfill
is easier to read and understand than the dynamic second argument, so I'll keep that. –
Litmus python -m timeit "format(255, 'b')"
: 154 nsec per loop. python -m timeit "bin(255)[2:]"
: 130 nsec per loop. –
Jaf bin
is consistently 20% faster, and on my AMD Ryzen 3 with Windows 10 and Python 3.7.4-32, 30%. –
Jaf I am surprised there is no mention of a nice way to accomplish this using formatting strings that are supported in Python 3.6 and higher. TLDR:
>>> number = 1
>>> f'0b{number:08b}'
'0b00000001'
This is functionality of formatting strings available from Python 3.6:
>>> x, y, z = 1, 2, 3
>>> f'{x} {y} {2*z}'
'1 2 6'
You can request binary as well:
>>> f'{z:b}'
'11'
Specify the width:
>>> f'{z:8b}'
' 11'
Request zero padding:
f'{z:08b}'
'00000011'
And add common prefix to signify binary number:
>>> f'0b{z:08b}'
'0b00000011'
You can also let Python add the prefix for you but I do not like it so much as the version above because you have to take the prefix into width consideration:
>>> f'{z:#010b}'
'0b00000011'
More info is available in official documentation on Formatted string literals and Format Specification Mini-Language.
f'0b{z:09_b}'
=> '0b0000_0011'
–
Naomanaomi f'{z:08b}'[::-1]
to achieve the least significant byte first ordering, however this will IMHO in most cases cause just confusion... –
Abraham timeit.timeit( 'f"{2:08b}"', number=10000000 ) => 1.1823169720000806
versus timeit.timeit( 'format(2,"08b")', number=10000000 ) => 1.3507722609992925
–
Ephesus As a reference:
def toBinary(n):
return ''.join(str(1 & int(n) >> i) for i in range(64)[::-1])
This function can convert a positive integer as large as 18446744073709551615
, represented as string '1111111111111111111111111111111111111111111111111111111111111111'
.
It can be modified to serve a much larger integer, though it may not be as handy as "{0:b}".format()
or bin()
.
A simple way to do that is to use string format, see this page.
>> "{0:b}".format(10)
'1010'
And if you want to have a fixed length of the binary string, you can use this:
>> "{0:{fill}8b}".format(10, fill='0')
'00001010'
If two's complement is required, then the following line can be used:
'{0:{fill}{width}b}'.format((x + 2**n) % 2**n, fill='0', width=n)
where n is the width of the binary string.
one-liner with lambda:
>>> binary = lambda n: '' if n==0 else binary(n/2) + str(n%2)
test:
>>> binary(5)
'101'
EDIT:
but then :(
t1 = time()
for i in range(1000000):
binary(i)
t2 = time()
print(t2 - t1)
# 6.57236599922
in compare to
t1 = time()
for i in range(1000000):
'{0:b}'.format(i)
t2 = time()
print(t2 - t1)
# 0.68017411232
''
with '0'
, but it will add a leading 0 for any number. –
Meissen As the preceding answers mostly used format(), here is an f-string implementation.
integer = 7
bit_count = 5
print(f'{integer:0{bit_count}b}')
Output:
00111
For convenience here is the python docs link for formatted string literals: https://docs.python.org/3/reference/lexical_analysis.html#f-strings.
Summary of alternatives:
n=42
assert "-101010" == format(-n, 'b')
assert "-101010" == "{0:b}".format(-n)
assert "-101010" == (lambda x: x >= 0 and str(bin(x))[2:] or "-" + str(bin(x))[3:])(-n)
assert "0b101010" == bin(n)
assert "101010" == bin(n)[2:] # But this won't work for negative numbers.
Contributors include John Fouhy, Tung Nguyen, mVChr, Martin Thoma. and Martijn Pieters.
str.format()
just to format one value is overkill. Go straight to the format()
function: format(n, 'b')
. No need to parse out the placeholder and match it to an argument that way. –
Lacy For those of us who need to convert signed integers (range -2**(digits-1) to 2**(digits-1)-1) to 2's complement binary strings, this works:
def int2bin(integer, digits):
if integer >= 0:
return bin(integer)[2:].zfill(digits)
else:
return bin(2**digits + integer)[2:]
This produces:
>>> int2bin(10, 8)
'00001010'
>>> int2bin(-10, 8)
'11110110'
>>> int2bin(-128, 8)
'10000000'
>>> int2bin(127, 8)
'01111111'
you can do like that :
bin(10)[2:]
or :
f = str(bin(10))
c = []
c.append("".join(map(int, f[2:])))
print c
Using numpy pack/unpackbits, they are your best friends.
Examples
--------
>>> a = np.array([[2], [7], [23]], dtype=np.uint8)
>>> a
array([[ 2],
[ 7],
[23]], dtype=uint8)
>>> b = np.unpackbits(a, axis=1)
>>> b
array([[0, 0, 0, 0, 0, 0, 1, 0],
[0, 0, 0, 0, 0, 1, 1, 1],
[0, 0, 0, 1, 0, 1, 1, 1]], dtype=uint8)
uint8
array into a binary-valued output array. So good for values up to 255. –
Conner The accepted answer didn't address negative numbers, which I'll cover. In addition to the answers above, you can also just use the bin and hex functions. And in the opposite direction, use binary notation:
>>> bin(37)
'0b100101'
>>> 0b100101
37
But with negative numbers, things get a bit more complicated. The question doesn't specify how you want to handle negative numbers.
Python just adds a negative sign so the result for -37 would be this:
>>> bin(-37)
'-0b100101'
In computer/hardware binary data, negative signs don't exist. All we have is 1's and 0's. So if you're reading or producing binary streams of data to be processed by other software/hardware, you need to first know the notation being used.
One notation is sign-magnitude notation, where the first bit represents the negative sign, and the rest is the actual value. In that case, -37 would be 0b1100101
and 37 would be 0b0100101
. This looks like what python produces, but just add a 0 or 1 in front for positive / negative numbers.
More common is Two's complement notation, which seems more complicated and the result is very different from python's string formatting. You can read the details in the link, but with an 8bit signed integer -37 would be 0b11011011
and 37 would be 0b00100101
.
Python has no easy way to produce these binary representations. You can use numpy to turn Two's complement binary values into python integers:
>>> import numpy as np
>>> np.int8(0b11011011)
-37
>>> np.uint8(0b11011011)
219
>>> np.uint8(0b00100101)
37
>>> np.int8(0b00100101)
37
But I don't know an easy way to do the opposite with builtin functions. The bitstring package can help though.
>>> from bitstring import BitArray
>>> arr = BitArray(int=-37, length=8)
>>> arr.uint
219
>>> arr.int
-37
>>> arr.bin
'11011011'
>>> BitArray(bin='11011011').int
-37
>>> BitArray(bin='11011011').uint
219
Python 3.6 added a new string formatting approach called formatted string literals or “f-strings”. Example:
name = 'Bob'
number = 42
f"Hello, {name}, your number is {number:>08b}"
Output will be 'Hello, Bob, your number is 00001010!'
A discussion of this question can be found here - Here
Yet another solution with another algorithm, by using bitwise operators.
def int2bin(val):
res=''
while val>0:
res += str(val&1)
val=val>>1 # val=val/2
return res[::-1] # reverse the string
A faster version without reversing the string.
def int2bin(val):
res=''
while val>0:
res = chr((val&1) + 0x30) + res
val=val>>1
return res
numpy.binary_repr(num, width=None)
Examples from the documentation link above:
>>> np.binary_repr(3) '11' >>> np.binary_repr(-3) '-11' >>> np.binary_repr(3, width=4) '0011'
The two’s complement is returned when the input number is negative and width is specified:
>>> np.binary_repr(-3, width=3) '101' >>> np.binary_repr(-3, width=5) '11101'
def binary(decimal) :
otherBase = ""
while decimal != 0 :
otherBase = str(decimal % 2) + otherBase
decimal //= 2
return otherBase
print binary(10)
output:
1010
Unless I'm misunderstanding what you mean by binary string I think the module you are looking for is struct
Here is the code I've just implemented. This is not a method but you can use it as a ready-to-use function!
def inttobinary(number):
if number == 0:
return str(0)
result =""
while (number != 0):
remainder = number%2
number = number/2
result += str(remainder)
return result[::-1] # to invert the string
Calculator with all neccessary functions for DEC,BIN,HEX: (made and tested with Python 3.5)
You can change the input test numbers and get the converted ones.
# CONVERTER: DEC / BIN / HEX
def dec2bin(d):
# dec -> bin
b = bin(d)
return b
def dec2hex(d):
# dec -> hex
h = hex(d)
return h
def bin2dec(b):
# bin -> dec
bin_numb="{0:b}".format(b)
d = eval(bin_numb)
return d,bin_numb
def bin2hex(b):
# bin -> hex
h = hex(b)
return h
def hex2dec(h):
# hex -> dec
d = int(h)
return d
def hex2bin(h):
# hex -> bin
b = bin(h)
return b
## TESTING NUMBERS
numb_dec = 99
numb_bin = 0b0111
numb_hex = 0xFF
## CALCULATIONS
res_dec2bin = dec2bin(numb_dec)
res_dec2hex = dec2hex(numb_dec)
res_bin2dec,bin_numb = bin2dec(numb_bin)
res_bin2hex = bin2hex(numb_bin)
res_hex2dec = hex2dec(numb_hex)
res_hex2bin = hex2bin(numb_hex)
## PRINTING
print('------- DECIMAL to BIN / HEX -------\n')
print('decimal:',numb_dec,'\nbin: ',res_dec2bin,'\nhex: ',res_dec2hex,'\n')
print('------- BINARY to DEC / HEX -------\n')
print('binary: ',bin_numb,'\ndec: ',numb_bin,'\nhex: ',res_bin2hex,'\n')
print('----- HEXADECIMAL to BIN / HEX -----\n')
print('hexadec:',hex(numb_hex),'\nbin: ',res_hex2bin,'\ndec: ',res_hex2dec,'\n')
Somewhat similar solution
def to_bin(dec):
flag = True
bin_str = ''
while flag:
remainder = dec % 2
quotient = dec / 2
if quotient == 0:
flag = False
bin_str += str(remainder)
dec = quotient
bin_str = bin_str[::-1] # reverse the string
return bin_str
here is simple solution using the divmod() fucntion which returns the reminder and the result of a division without the fraction.
def dectobin(number):
bin = ''
while (number >= 1):
number, rem = divmod(number, 2)
bin = bin + str(rem)
return bin
dectobin(10)
resulted in '0101' –
Pulverize Here's yet another way using regular math, no loops, only recursion. (Trivial case 0 returns nothing).
def toBin(num):
if num == 0:
return ""
return toBin(num//2) + str(num%2)
print ([(toBin(i)) for i in range(10)])
['', '1', '10', '11', '100', '101', '110', '111', '1000', '1001']
0
returns ''
, it should be '0'
... –
Cerebration To calculate binary of numbers:
print("Binary is {0:>08b}".format(16))
To calculate the Hexa decimal of a number:
print("Hexa Decimal is {0:>0x}".format(15))
To Calculate all the binary no till 16::
for i in range(17):
print("{0:>2}: binary is {0:>08b}".format(i))
To calculate Hexa decimal no till 17
for i in range(17):
print("{0:>2}: Hexa Decimal is {0:>0x}".format(i))
##as 2 digit is enogh for hexa decimal representation of a number
try:
while True:
p = ""
a = input()
while a != 0:
l = a % 2
b = a - l
a = b / 2
p = str(l) + p
print(p)
except:
print ("write 1 number")
I found a method using matrix operation to convert decimal to binary.
import numpy as np
E_mat = np.tile(E,[1,M])
M_order = pow(2,(M-1-np.array(range(M)))).T
bindata = np.remainder(np.floor(E_mat /M_order).astype(np.int),2)
E
is input decimal data,M
is the binary orders. bindata
is output binary data, which is in a format of 1 by M binary matrix.
I feel Martijn Pieter's comment deserves to be highlighted as an answer:
binary_string = format(value, '0{}b'.format(width))
To me is is both clear and versatile.
If you are willing to give up "pure" Python but gain a lot of firepower, there is Sage - example here:
sage: a = 15
sage: a.binary()
'1111'
You'll note that it returns as a string, so to use it as a number you'd want to do something like
sage: eval('0b'+b)
15
Here's a simple binary to decimal converter that continuously loops
t = 1
while t > 0:
binaryNumber = input("Enter a binary No.")
convertedNumber = int(binaryNumber, 2)
print(convertedNumber)
print("")
This is my answer it works well..!
def binary(value) :
binary_value = ''
while value !=1 :
binary_value += str(value%2)
value = value//2
return '1'+binary_value[::-1]
0
? E.g. binary(0)
will you get what you expect? –
Cerebration Along a similar line to Yusuf Yazici's answer
def intToBin(n):
if(n < 0):
print "Sorry, invalid input."
elif(n == 0):
print n
else:
result = ""
while(n != 0):
result += str(n%2)
n /= 2
print result[::-1]
I adjusted it so that the only variable being mutated is result (and n of course).
If you need to use this function elsewhere (i.e., have the result used by another module), consider the following adjustment:
def intToBin(n):
if(n < 0):
return -1
elif(n == 0):
return str(n)
else:
result = ""
while(n != 0):
result += str(n%2)
n //= 2 #added integer division
return result[::-1]
So -1 will be your sentinel value indicating the conversion failed. (This is assuming you are converting ONLY positive numbers, whether they be integers or longs).
Here is a (debugged) program that uses divmod
to construct a binary list:
Program
while True:
indecimal_str = input('Enter positive(decimal) integer: ')
if indecimal_str == '':
raise SystemExit
indecimal_save = int(indecimal_str)
if indecimal_save < 1:
print('Rejecting input, try again')
print()
continue
indecimal = int(indecimal_str)
exbin = []
print(indecimal, '<->', exbin)
while True:
if indecimal == 0:
print('Conversion:', indecimal_save, '=', "".join(exbin))
print()
break
indecimal, r = divmod(indecimal, 2)
if r == 0:
exbin.insert(0, '0')
else:
exbin.insert(0, '1')
print(indecimal, '<->', exbin)
Output
Enter positive(decimal) integer: 8
8 <-> []
4 <-> ['0']
2 <-> ['0', '0']
1 <-> ['0', '0', '0']
0 <-> ['1', '0', '0', '0']
Conversion: 8 = 1000
Enter positive(decimal) integer: 63
63 <-> []
31 <-> ['1']
15 <-> ['1', '1']
7 <-> ['1', '1', '1']
3 <-> ['1', '1', '1', '1']
1 <-> ['1', '1', '1', '1', '1']
0 <-> ['1', '1', '1', '1', '1', '1']
Conversion: 63 = 111111
Enter positive(decimal) integer: 409
409 <-> []
204 <-> ['1']
102 <-> ['0', '1']
51 <-> ['0', '0', '1']
25 <-> ['1', '0', '0', '1']
12 <-> ['1', '1', '0', '0', '1']
6 <-> ['0', '1', '1', '0', '0', '1']
3 <-> ['0', '0', '1', '1', '0', '0', '1']
1 <-> ['1', '0', '0', '1', '1', '0', '0', '1']
0 <-> ['1', '1', '0', '0', '1', '1', '0', '0', '1']
Conversion: 409 = 110011001
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