Python中的 numpy.left_shift()

numpy.left_shift()函数用于将整数的位向左移动。

通过在 arr1 的右侧附加 arr2 0s（零），这些位向左移动。由于数字的内部表示是二进制格式，所以这个操作相当于 arr1 乘以 2**arr2。例如，如果数字是 5，我们想要左移 2 位，那么在左移 2 位之后，结果将是 5*(2^2) = 20

Syntax : numpy.left_shift(arr1, arr2, /, out=None, *, where=True, casting=’same_kind’, order=’K’, dtype=None, ufunc ‘left_shift’)

Parameters :
arr1 : array_like of integer type
arr2 : array_like of integer type
Number of zeros to append to arr1.The value of arr2 should be positive integer.

out : [ndarray, optional] A location into which the result is stored.
  -> If provided, it must have a shape that the inputs broadcast to.
  -> If not provided or None, a freshly-allocated array is returned.

**kwargs : allows you to pass keyword variable length of argument to a function. It is used when we want to handle named argument in a function.

where : [array_like, optional]True value means to calculate the universal functions(ufunc) at that position, False value means to leave the value in the output alone.

Return : array of integer type.
Return arr1 with bits shifted arr2 times to the left. This is a scalar if both arr1 and arr2 are scalars.

代码#1：工作

# Python program explaining
# left_shift() function
  
import numpy as geek
in_num = 5
bit_shift = 2
  
print ("Input  number : ", in_num)
print ("Number of bit shift : ", bit_shift ) 
    
out_num = geek.left_shift(in_num, bit_shift) 
print ("After left shifting 2 bit  : ", out_num) 

输出 ：

Input  number :  5
Number of bit shift :  2
After left shifting 2 bit  :  20

代码#2：

# Python program explaining
# left_shift() function
  
import numpy as geek
  
in_arr = [2, 8, 15]
bit_shift =[3, 4, 5]
   
print ("Input array : ", in_arr) 
print ("Number of bit shift : ", bit_shift)
    
out_arr = geek.left_shift(in_arr, bit_shift) 
print ("Output array after left shifting: ", out_arr) 

输出 ：

Input array :  [2, 8, 15]
Number of bit shift :  [3, 4, 5]
Output array after left shifting:  [ 16 128 480]