我正在使用Python编写一个动态数组实现(类似于内置的列表类),需要观察容量的增长(每次达到极限时会加倍)。为此,我有以下代码,但输出很奇怪。看起来
问题出在哪里?
测试大小调整的代码:
sys.getsizeof()
从不调用我的类的__sizeof__()
。为了测试,我让__sizeof__()
返回0
,但根据sys.getsizeof()
它是非零的。问题出在哪里?
import ctypes
class DynamicArray(object):
'''
DYNAMIC ARRAY CLASS (Similar to Python List)
'''
def __init__(self):
self.n = 0 # Count actual elements (Default is 0)
self.capacity = 1 # Default Capacity
self.A = self.make_array(self.capacity)
def __len__(self):
"""
Return number of elements sorted in array
"""
return self.n
def __getitem__(self,k):
"""
Return element at index k
"""
if not 0 <= k <self.n:
return IndexError('K is out of bounds!') # Check it k index is in bounds of array
return self.A[k] #Retrieve from array at index k
def append(self, ele):
"""
Add element to end of the array
"""
if self.n == self.capacity:
self._resize(2*self.capacity) #Double capacity if not enough room
self.A[self.n] = ele #Set self.n index to element
self.n += 1
def _resize(self,new_cap):
"""
Resize internal array to capacity new_cap
"""
print("resize called!")
B = self.make_array(new_cap) # New bigger array
for k in range(self.n): # Reference all existing values
B[k] = self.A[k]
self.A = B # Call A the new bigger array
self.capacity = new_cap # Reset the capacity
def make_array(self,new_cap):
"""
Returns a new array with new_cap capacity
"""
return (new_cap * ctypes.py_object)()
def __sizeof__(self):
return 0
测试大小调整的代码:
arr2 = DynamicArray()
import sys
for i in range(100):
print(len(arr2), " ", sys.getsizeof(arr2))
arr2.append(i)
输出结果如下:
0 24
1 24
resize called!
2 24
resize called!
3 24
4 24
resize called!
5 24
6 24
7 24
8 24
resize called!
9 24
10 24
11 24
12 24
13 24
14 24
15 24
16 24
resize called!
17 24
18 24
19 24
20 24
21 24
22 24
23 24
24 24
25 24
26 24
27 24
28 24
29 24
30 24
31 24
32 24
resize called!
33 24
34 24
35 24
36 24
37 24
38 24
39 24
40 24
41 24
42 24
43 24
44 24
45 24
46 24
47 24
48 24
49 24
50 24
51 24
52 24
53 24
54 24
55 24
56 24
57 24
58 24
59 24
60 24
61 24
62 24
63 24
64 24
resize called!
65 24
66 24
67 24
68 24
69 24
70 24
71 24
72 24
73 24
74 24
75 24
76 24
77 24
78 24
79 24
80 24
81 24
82 24
83 24
84 24
85 24
86 24
87 24
88 24
89 24
90 24
91 24
92 24
93 24
94 24
95 24
96 24
97 24
98 24
99 24
__sizeof __()
返回一个非零值,你会发现观察到的值增加了这个数量。 - Leonsys.getsizeof()
在默认实现下会返回0?它不应该调用像sizeof()
这样的 C 函数来计算大小吗? - Cherrymelon