def __len__(self): return len(self.memory)是什么意思
时间: 2024-06-07 11:11:03 浏览: 18
这是一个Python类中的方法,它的作用是返回该类对象的memory属性的长度。通常情况下,如果一个类要支持Python的内置函数len(),就需要实现该类的__len__()方法。
在该代码中,__len__()方法被定义在一个自定义的类中,该类的实例对象(称为对象)具有一个名为memory的属性。当该类的对象调用len()函数时,Python解释器会查找是否有__len__()方法的实现,如果有,则调用该方法,并返回方法执行的结果,即返回对象memory属性的长度。
因此,代码的含义是:当使用len()函数计算该类对象的长度时,返回该对象的memory属性的长度。
相关问题
#256个block memory_size = 256 #pid进程号 class Process: def __init__(self, pid, block, duration): self.__block = block self.__duration = duration self.__pid = pid self.__memory = None @property def pid(self): return self.__pid @property def block(self): return self.__block @property def duration(self): return self.__duration def set_memory(self, memory_start, memory_end): self.__memory = (memory_start, memory_end) def get_memory(self): return self.__memory class MemoryAllocator: def __init__(self, memory_size): self.__memory_blocks = [None] * memory_size def memory_view(self): '''return the array of the use of memory blocks.''' return tuple(self.__memory_blocks) def allocate_memory(self, block_start, length, process): for block_id in range(block_start, block_start+length): assert self.__memory_blocks[block_id] is None, 'tend to allocate occupied blocks' self.__memory_blocks[block_id] = process process.set_memory(block_start, length) def free_memory(self, process): assert process.get_memory() is not None, 'process should already hold memory blocks' block_start, length = process.get_memory() for block_id in range(block_start, block_start+length): assert self.__memory_blocks[block_id] == process, 'the orresponding memory blocks should be assigned to the process' self.__memory_blocks[block_id] = None
这段代码实现了一个简单的内存分配器和进程类。其中,内存分配器使用一个数组来表示内存块的使用情况,每个进程对象都包含一个指向内存块的引用。
这段代码的实现还可以进行一些改进:
1. 内存分配器可以使用更高效的数据结构,比如位图,来表示内存块的使用情况。
2. 进程类可以添加一个方法来释放内存,而不是在内存分配器中实现。
3. 内存分配器可以添加一个方法来查找可用的内存块,而不是在进程类中实现。
4. 进程类可以将内存块的起始位置和长度作为属性,而不是在set_memory方法中设置。
下面是改进后的代码:
```
class Process:
def __init__(self, pid, duration):
self.__pid = pid
self.__duration = duration
self.__memory_start = None
self.__memory_length = None
@property
def pid(self):
return self.__pid
@property
def duration(self):
return self.__duration
@property
def memory_start(self):
return self.__memory_start
@property
def memory_length(self):
return self.__memory_length
def set_memory(self, start, length):
self.__memory_start = start
self.__memory_length = length
def release_memory(self):
self.__memory_start = None
self.__memory_length = None
class MemoryAllocator:
def __init__(self, memory_size):
self.__memory_blocks = [False] * memory_size
def find_free_memory(self, length):
for i in range(len(self.__memory_blocks) - length + 1):
if all(not self.__memory_blocks[j] for j in range(i, i + length)):
return i
return None
def allocate_memory(self, process):
length = process.duration
start = self.find_free_memory(length)
assert start is not None, 'allocation failed'
for i in range(start, start + length):
self.__memory_blocks[i] = True
process.set_memory(start, length)
def free_memory(self, process):
start = process.memory_start
length = process.memory_length
for i in range(start, start + length):
self.__memory_blocks[i] = False
process.release_memory()
```
改进后的代码更加清晰和易于维护,也更加高效。
优化class MemoryManager: def __init__(self, allocator): self.allocator = allocator def allocate(self, process, request_size): memory_view = self.allocator.memory_view() block_start = None for i in range(len(memory_view)): if memory_view[i] is None: if block_start is None: block_start = i if i - block_start + 1 == request_size: self.allocator.allocate_memory(block_start, request_size, process) else: block_start = None return None
好的,下面是我为 `MemoryManager` 类做的优化:
```python
class MemoryManager:
def __init__(self, allocator):
self.allocator = allocator
def allocate(self, process, request_size):
memory_view = self.allocator.memory_view()
block_start = None
for i, block in enumerate(memory_view):
if block is None:
if block_start is None:
block_start = i
if i - block_start + 1 == request_size:
self.allocator.allocate_memory(block_start, request_size, process)
return block_start
else:
block_start = None
return None
```
优化部分如下:
1. 使用了 `enumerate` 函数来同时遍历索引和元素,避免了使用 `range(len(memory_view))` 的复杂写法。
2. 对于空闲内存块的判断,使用了直接判断元素是否为 None 的方式,避免了使用 `is` 的复杂写法。
3. 对于连续的空闲内存块的查找,使用了一个变量来记录当前空闲块的起始位置,而不是在分配内存时再次遍历内存块。这样可以提高效率,避免了重复访问内存块的开销。