方法一 int.from_bytes(v.to_bytes)

# 将占1字节的小端有符号数-43转换成无符号数小端整数213
int.from_bytes((-43).to_bytes(1, 'little', signed=True), 'little', signed=False)
# 213

注意区别大小端

'''
to_bytes(length, byteorder, *, signed=False) method of builtins.int instance
    Return an array of bytes representing an integer.
    length
      Length of bytes object to use.  An OverflowError is raised if the
      integer is not representable with the given number of bytes.  # 字节长度
    byteorder
      The byte order used to represent the integer.  If byteorder is 'big',
      the most significant byte is at the beginning of the byte array.  If
      byteorder is 'little', the most significant byte is at the end of the
      byte array.  To request the native byte order of the host system, use
      `sys.byteorder' as the byte order value.  # 大小端
    signed
      Determines whether two's complement is used to represent the integer.
      If signed is False and a negative integer is given, an OverflowError
      is raised.  # 是否是符号数
  '''
  '''
  from_bytes(bytes, byteorder, *, signed=False) method of builtins.type instance
    Return the integer represented by the given array of bytes.
    
    bytes
      Holds the array of bytes to convert.  The argument must either
      support the buffer protocol or be an iterable object producing bytes.
      Bytes and bytearray are examples of built-in objects that support the
      buffer protocol.
    byteorder
      The byte order used to represent the integer.  If byteorder is 'big',
      the most significant byte is at the beginning of the byte array.  If
      byteorder is 'little', the most significant byte is at the end of the
      byte array.  To request the native byte order of the host system, use
      `sys.byteorder' as the byte order value.
    signed
      Indicates whether two's complement is used to represent the integer.
  '''

方法二 使用struct类库

>>> import struct
>>> struct.unpack('<B', struct.pack('<b', -43))
(213,)
# 返回的是一个元祖

第一个参数是fmt,可选项如下
DESCRIPTION
Functions to convert between Python values and C structs.
Python bytes objects are used to hold the data representing the C struct
and also as format strings (explained below) to describe the layout of data
in the C struct.

The optional first format char indicates byte order, size and alignment:
  @: native order, size & alignment (default)
  =: native order, std. size & alignment
  <: little-endian, std. size & alignment
  >: big-endian, std. size & alignment
  !: same as >

The remaining chars indicate types of args and must match exactly;
these can be preceded by a decimal repeat count:
  x: pad byte (no data); c:char; b:signed byte; B:unsigned byte;
  ?: _Bool (requires C99; if not available, char is used instead)
  h:short; H:unsigned short; i:int; I:unsigned int;
  l:long; L:unsigned long; f:float; d:double; e:half-float.
Special cases (preceding decimal count indicates length):
  s:string (array of char); p: pascal string (with count byte).
Special cases (only available in native format):
  n:ssize_t; N:size_t;
  P:an integer type that is wide enough to hold a pointer.
Special case (not in native mode unless 'long long' in platform C):
  q:long long; Q:unsigned long long
Whitespace between formats is ignored.

The variable struct.error is an exception raised on errors.

方法三 &操作符

>>> -43 & 255
213
>>> -43 & 0xff
213
-43 & 0xffff
65493