固定数组索引在Python [英] Fixing array indices in Python

问题描述

我想有发言权，从4索引启动阵列和去9.我不感兴趣，在与LT建立内存空间; 4，如何最好继续吗？我的2D code是如下：

I'd like to have arrays that start from say an index of 4 and go to 9. I'm not interested in creating memory space for < 4, so how is best to proceed? My 2D code is as follows:

arr = [[ 0 for row in range(2)] for col in range(1, 129)]
>>> arr[0][0] = 1
>>> arr[128][0] = 1
Traceback (most recent call last):
  File "<stdin>", line 1, in ?
IndexError: list index out of range
>>> arr[127][0] = 1

如何选择只使用特定范围，即其中最后一个指数从1到128（含）不为0到127这可能是显而易见的，但有没有办法做到这一点？

How can selectively just use the specific range i.e. where the last index runs from 1 to 128 inclusive not 0 to 127. This maybe obvious, but is there a way to do this?

感谢您的建议的类型的字典，我一直避免这些 - 我知道 - 大部分code，我转换的是C，但我认为可能的字典的救星。有没有办法做什么，我使用数组问？

Thanks for the suggestion for dicts, I have been avoiding these - I know - much of the code I'm converting is from C, but I think dictionaries might the saviour. Is there a way to do what I am asking with arrays?

推荐答案

您可以简单的模拟列表：

class OffsetList(object):
  def __init__(self, offset=4):
    self._offset = offset
    self._lst = []
  def __len__(self):
    return len(self._lst)
  def __getitem__(self, key):
    return self._lst[key - self._offset]
  def __setitem__(self, key, val):
    self._lst[key - self._offset] = val
  def __delitem__(self, key):
    del self._lst[key - self._offset]
  def __iter__(self):
    return iter(self._lst)
  def __contains__(self, item):
    return item in self._lst

  # All other methods go to the backing list.
  def __getattr__(self, a):
    return getattr(self._lst, a)

# Test it like this:
ol = OffsetList(4)
ol.append(2)
assert ol[4] == 2
assert len(ol) == 1

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