我可以看到在Python中有两种非常相似的属性方式。
(a) 属性类
class Location(object):
def __init__(self, longitude, latitude):
self.set_latitude(latitude)
self.set_longitude(longitude)
def set_latitude(self, latitude):
if not (-90 <= latitude <= 90):
raise ValueError('latitude was {}, but has to be in [-90, 90]'
.format(latitude))
self._latitude = latitude
def set_longitude(self, longitude):
if not (-180 <= longitude <= 180):
raise ValueError('longitude was {}, but has to be in [-180, 180]'
.format(longitude))
self._longitude = longitude
def get_longitude(self):
return self._latitude
def get_latitude(self):
return self._longitude
latitude = property(get_latitude, set_latitude)
longitude = property(get_longitude, set_longitude)
(b)属性装饰器
class Location(object):
def __init__(self, longitude, latitude):
self.latitude = latitude
self.longitude = latitude
@property
def latitude(self):
"""I'm the 'x' property."""
return self._latitude
@property
def longitude(self):
"""I'm the 'x' property."""
return self._longitude
@latitude.setter
def latitude(self, latitude):
if not (-90 <= latitude <= 90):
raise ValueError('latitude was {}, but has to be in [-90, 90]'
.format(latitude))
self._latitude = latitude
@longitude.setter
def longitude(self, longitude):
if not (-180 <= longitude <= 180):
raise ValueError('longitude was {}, but has to be in [-180, 180]'
.format(longitude))
self._longitude = longitude
问题
这两段代码是否相同（例如，字节码上）？它们显示相同的行为吗？
有没有官方指南，指导应该使用哪种“风格”？
其中一个优于另一个的真正优势是什么？
我尝试过的
py_compile + uncompyle6
我已经编译了这两个版本：
>>> import py_compile
>>> py_compile.compile('test.py')
我尝试了使用 uncompyle6 对两个文件进行反编译，但返回的结果与原始内容相同（仅格式略有不同）。
import + dis
我还尝试了以下方法：
import test # (a)
import test2 # (b)
dis.dis(test)
dis.dis(test2)
我对test2的输出非常困惑:
Disassembly of Location:
Disassembly of __init__:
13 0 LOAD_FAST 2 (latitude)
2 LOAD_FAST 0 (self)
4 STORE_ATTR 0 (latitude)
14 6 LOAD_FAST 2 (latitude)
8 LOAD_FAST 0 (self)
10 STORE_ATTR 1 (longitude)
12 LOAD_CONST 0 (None)
14 RETURN_VALUE
第一个比较大:
Disassembly of Location:
Disassembly of __init__:
13 0 LOAD_FAST 0 (self)
2 LOAD_ATTR 0 (set_latitude)
4 LOAD_FAST 2 (latitude)
6 CALL_FUNCTION 1
8 POP_TOP
14 10 LOAD_FAST 0 (self)
12 LOAD_ATTR 1 (set_longitude)
14 LOAD_FAST 1 (longitude)
16 CALL_FUNCTION 1
18 POP_TOP
20 LOAD_CONST 0 (None)
22 RETURN_VALUE
Disassembly of set_latitude:
17 0 LOAD_CONST 3 (-90)
2 LOAD_FAST 1 (latitude)
4 DUP_TOP
6 ROT_THREE
8 COMPARE_OP 1 (<=)
10 JUMP_IF_FALSE_OR_POP 18
12 LOAD_CONST 1 (90)
14 COMPARE_OP 1 (<=)
16 JUMP_FORWARD 4 (to 22)
>> 18 ROT_TWO
20 POP_TOP
>> 22 POP_JUMP_IF_TRUE 38
18 24 LOAD_GLOBAL 0 (ValueError)
26 LOAD_CONST 2 ('latitude was {}, but has to be in [-90, 90]')
28 LOAD_ATTR 1 (format)
30 LOAD_FAST 1 (latitude)
32 CALL_FUNCTION 1
34 CALL_FUNCTION 1
36 RAISE_VARARGS 1
19 >> 38 LOAD_FAST 1 (latitude)
40 LOAD_FAST 0 (self)
42 STORE_ATTR 2 (latitude)
44 LOAD_CONST 0 (None)
46 RETURN_VALUE
Disassembly of set_longitude:
22 0 LOAD_CONST 3 (-180)
2 LOAD_FAST 1 (longitude)
4 DUP_TOP
6 ROT_THREE
8 COMPARE_OP 1 (<=)
10 JUMP_IF_FALSE_OR_POP 18
12 LOAD_CONST 1 (180)
14 COMPARE_OP 1 (<=)
16 JUMP_FORWARD 4 (to 22)
>> 18 ROT_TWO
20 POP_TOP
>> 22 POP_JUMP_IF_TRUE 38
23 24 LOAD_GLOBAL 0 (ValueError)
26 LOAD_CONST 2 ('longitude was {}, but has to be in [-180, 180]')
28 LOAD_ATTR 1 (format)
30 LOAD_FAST 1 (longitude)
32 CALL_FUNCTION 1
34 CALL_FUNCTION 1
36 RAISE_VARARGS 1
24 >> 38 LOAD_FAST 1 (longitude)
40 LOAD_FAST 0 (self)
42 STORE_ATTR 2 (longitude)
44 LOAD_CONST 0 (None)
46 RETURN_VALUE
这种差异是从哪里来的？第一个示例的值范围检查在哪里？
Location().latitude = 10将绕过任何set_latitude所做的验证。set_latitude甚至不会被调用。 - DeepSpacetimeit模块来查看哪个更快，以及差距有多大。生成的字节码对性能的影响可能并不重要。 - martineau