Python实现B树索引
时间: 2023-11-19 19:38:59 浏览: 27
B树(B-tree)是一种自平衡的搜索树,常用于数据库和文件系统中的索引结构。下面是一个简单的Python实现B树索引的示例代码:
```python
class BTreeNode:
def __init__(self, leaf=False):
self.leaf = leaf
self.keys = []
self.child = []
class BTree:
def __init__(self, t):
self.root = BTreeNode(True)
self.t = t
def insert(self, k):
root = self.root
if len(root.keys) == (2 * self.t) - 1:
temp = BTreeNode()
self.root = temp
temp.child.insert(0, root)
self._split_child(temp, 0)
self._insert_non_full(temp, k)
else:
self._insert_non_full(root, k)
def _insert_non_full(self, x, k):
i = len(x.keys) - 1
if x.leaf:
x.keys.append((None, None))
while i >= 0 and k < x.keys[i]:
x.keys[i + 1] = x.keys[i]
i -= 1
x.keys[i + 1] = k
else:
while i >= 0 and k < x.keys[i]:
i -= 1
i += 1
if len(x.child[i].keys) == (2 * self.t) - 1:
self._split_child(x, i)
if k > x.keys[i]:
i += 1
self._insert_non_full(x.child[i], k)
def _split_child(self, x, i):
t = self.t
y = x.child[i]
z = BTreeNode(y.leaf)
x.child.insert(i + 1, z)
x.keys.insert(i, y.keys[t - 1])
z.keys = y.keys[t: (2 * t) - 1]
y.keys = y.keys[0: t - 1]
if not y.leaf:
z.child = y.child[t: 2 * t]
y.child = y.child[0: t - 1]
def search(self, k, x=None):
if isinstance(x, BTreeNode):
i = 0
while i < len(x.keys) and k > x.keys[i]:
i += 1
if i < len(x.keys) and k == x.keys[i]:
return x, i
elif x.leaf:
return None
else:
return self.search(k, x.child[i])
else:
return self.search(k, self.root)
# 使用示例
btree = BTree(t=3)
btree.insert(10)
btree.insert(20)
btree.insert(5)
btree.insert(6)
result = btree.search(6)
if result:
node, index = result
print(f"找到了,节点: {node.keys[index]}")
else:
print("未找到")
```
这个示例实现了一个B树索引的基本功能,包括插入和搜索操作。你可以根据需要进行扩展和修改。注意,这只是一个简单的实现,实际使用中可能需要考虑更多细节和优化。