Python int转换为二进制字符串？

Are there any canned Python methods to convert an Integer (or Long) into a binary string in Python?

There are a myriad of dec2bin() functions out on Google… But I was hoping I could use a built-in function / library.

Python’s string format method can take a format spec.

>>> "{0:b}".format(37)
'100101'

Format spec docs for Python 2

Format spec docs for Python 3

If you’re looking for as an equivalent to hex(), it was added in python 2.6.

Example:

>>> bin(10)
'0b1010'

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):

• the language or built-in libraries.
• third-party libraries with suitable licenses.
• your own collection.
• something new you need to write (and save in your own collection for later).

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)

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.

This is for python 3 and it keeps the leading zeros !

print(format(0, '08b'))

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

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.

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.

>>> format(123, 'b')
'1111011'

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)

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'

Unless I’m misunderstanding what you mean by binary string I think the module you are looking for is struct

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 

def binary(decimal) :
    otherBase = ""
    while decimal != 0 :
        otherBase  =  str(decimal % 2) + otherBase
        decimal    //=  2
    return otherBase

print binary(10)

output:

1010

you can do like that :

bin(10)[2:]

or :

f = str(bin(10))
c = []
c.append("".join(map(int, f[2:])))
print c

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

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

n=input()
print(bin(n).replace("0b", ""))

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'

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’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']

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')

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

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

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)

Eis input decimal data,M is the binary orders. bindata is output binary data, which is in a format of 1 by M binary matrix.

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]