I want Python to bit shift the entire 32 one-dimensional arrays.

Asked 2 months ago, Updated 2 months ago, 4 views

Thank you for your help.

[Used language]

Python 3

[What do you want to do?]

Now
in the Byte (8-bit) length array (list) variable a[32]   If you consider the entire 32 Byte to be a 256-bit column,
  I'd like to have this whole bit string right shift.
  How can I do this?


in Python or numpy or scipy   Is there a function that can be converted once?

Thank you for your cooperation.

python

2022-09-30 14:14

3 Answers

The following is an example of a 5-bit right shift.After converting the byte string to a 256-bit length integer value and shifting it back to an integer value in 8-bit increments.

>>import re

>>>lst=list(iter(b'@12Hello World, Good bye World.'))
>>>lst
[64, 49, 50, ..., 108, 100, 46]
>>len(lst)
32

>> list (map(lambdax:int(x,2),
     re.findall('.{8},
       format(sum([int(x)*(2**(8*(len(lst)-i-1))))for i, x in enumerate(lst)])>5, '0256b')
     )))
[2, 1, 137, ..., 147, 99, 33]

This may be difficult to understand, so I will try to shift right, for example, 32-bit (4 bytes).

>>shifted=list(map(lambdax:int(x,2),
     re.findall('.{8},
       format(sum([int(x)*(2**(8*(len(lst)-i-1))))for i, x in enumerate(lst)))>>32, '0256b')
     )))

>> str('.join(map(chr,shifted)))
'\x00\x00\x00\x00 @12 Hello World, Goodbye Wo'


2022-09-30 14:14

I tried to implement it from the perspective that 32 int8s are collected and 256bit ints.
The example is only 32 bits long, but can be extended to any length

#-*-coding:utf-8-*-

import numpy as np

DIGITS = 8

defprint_bits(bits):
    For bit in bits:
        print np.binary_repr(bit).zfill(DIGITS)

# shift to the right to get the vanishing bit (left-hand side)
def get_underflow_bits(bits,n):
    return np.bitwise_and (2**DIGITS-1, np.left_shift (bits, DIGITS-n))

# Returns only bits moved to the next array as a result of the right shift
def get_underflows(bits,n):
    return np.insert(get_underflow_bits(bits,n),0,0)[:-1]

# Take OR of simple right-shift results and shift
default_shift(bits,n):
    return np.bitwise_or(np.right_shift(bits,n), get_underflows(bits,n))

sample = [255,0,255,0]
print_bits(right_shift(sample,3))


2022-09-30 14:14

This is an implementation that creates a large integer once and then shifts it to the right to return it to the array.For your information.

 from functools import redundancy


default(a, bits):
    D = 8
    n = len(a)
    value=reduce(lambdax, y:x|y, (e<<(D*(n-1-i))for i, e in enumerate(a))))
    value>>=bits
    s = '{:0 {}b}'.format(value, len(a)*D)
    return [ int[i*D:(i+1)*D], 2) for i in range(n)]


a = [0b11111111, 0b010101, 0b00001111]
print(''.join('{:08b}'.format(x) for x in shift(a,0)))#111111101010100001111
print(''.join('{:08b}'.format(x) for x in shift(a,1)))#011111110101010000111
print(''.join('{:08b}'.format(x) for x in shift(a,2)))#0011111111010101000011
print(''.join('{:08b}'.format(x) for x in shift(a,3)))#00011111111010101010100001
print(''.join('{:08b}'.format(x) for x in shift(a,4)))#000011111111111101010101010000
print(''.join('{:08b}'.format(x) for x in shift(a,5)))#000001111111010101000
print(''.join('{:08b}'.format(x) for x in shift(a,6)))#00000011111111110101010100
print(''.join('{:08b}'.format(x) for x in shift(a,7)))#00000001 1111111010101010
print(''.join('{:08b}'.format(x) for x in shift(a,8)))#000000001111111110101
print(''.join('{:08b}'.format(x) for x in shift(a,9)))#00000000111111101010
print(''.join('{:08b}'.format(x) for x in shift(a,10)))#000000000011111111010101


2022-09-30 14:14

If you have any answers or tips


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