我有一个使用GDAL模块打开一个大型光栅图像的类(https:/pypi.orgprojectGDAL。),并从中提取一些位置的小图像,这些位置由传递的坐标元组列表定义。我想使用Pathos来处理一个大的坐标列表,就像我的代码的这个简化版本一样。
import gdal
import pathos.pools as pp
class MyClass:
def __init__(self, image):
self.image_object = gdal.Open(image)
def get_small_image(self, coord, size=100):
small_image = self.image_object.ReadAsArray(coord[0], coord[1], size, size)
return small_image
def run_multi(self, coords_in):
pool = pp.ProcessPool(2)
output = pool.map(self.get_small_image, coords_in)
return output
image = r'C:\path\to\image.JP2'
class_obj = MyClass(image)
coords = [(200, 200), (400, 400), (600, 600), (800, 800)]
results = class_obj.run_multi(coords)
print(results)
运行这段代码时,出现了以下错误
Traceback (most recent call last):
File "C:/Users/lharris/PycharmProjects/road_condition_py3/error_recreate.py", line 26, in <module>
results = class_obj.run_multi(coords)
File "C:/Users/lharris/PycharmProjects/road_condition_py3/error_recreate.py", line 17, in run_multi
output = pool.map(self.get_small_image, coords_in)
File "C:\Users\lharris\PycharmProjects\road_condition_py3\venv\lib\site-packages\pathos\multiprocessing.py", line 137, in map
return _pool.map(star(f), zip(*args)) # chunksize
File "C:\Users\lharris\PycharmProjects\road_condition_py3\venv\lib\site-packages\multiprocess\pool.py", line 266, in map
return self._map_async(func, iterable, mapstar, chunksize).get()
File "C:\Users\lharris\PycharmProjects\road_condition_py3\venv\lib\site-packages\multiprocess\pool.py", line 644, in get
raise self._value
File "C:\Users\lharris\PycharmProjects\road_condition_py3\venv\lib\site-packages\multiprocess\pool.py", line 424, in _handle_tasks
put(task)
File "C:\Users\lharris\PycharmProjects\road_condition_py3\venv\lib\site-packages\multiprocess\connection.py", line 209, in send
self._send_bytes(_ForkingPickler.dumps(obj))
File "C:\Users\lharris\PycharmProjects\road_condition_py3\venv\lib\site-packages\multiprocess\reduction.py", line 54, in dumps
cls(buf, protocol).dump(obj)
File "C:\Python36\lib\pickle.py", line 409, in dump
self.save(obj)
File "C:\Python36\lib\pickle.py", line 476, in save
f(self, obj) # Call unbound method with explicit self
File "C:\Python36\lib\pickle.py", line 751, in save_tuple
save(element)
File "C:\Python36\lib\pickle.py", line 476, in save
f(self, obj) # Call unbound method with explicit self
File "C:\Python36\lib\pickle.py", line 736, in save_tuple
save(element)
File "C:\Python36\lib\pickle.py", line 476, in save
f(self, obj) # Call unbound method with explicit self
File "C:\Python36\lib\pickle.py", line 736, in save_tuple
save(element)
File "C:\Python36\lib\pickle.py", line 476, in save
f(self, obj) # Call unbound method with explicit self
File "C:\Users\lharris\PycharmProjects\road_condition_py3\venv\lib\site-packages\dill\_dill.py", line 1377, in save_function
obj.__dict__), obj=obj)
File "C:\Python36\lib\pickle.py", line 610, in save_reduce
save(args)
File "C:\Python36\lib\pickle.py", line 476, in save
f(self, obj) # Call unbound method with explicit self
File "C:\Python36\lib\pickle.py", line 751, in save_tuple
save(element)
File "C:\Python36\lib\pickle.py", line 476, in save
f(self, obj) # Call unbound method with explicit self
File "C:\Python36\lib\pickle.py", line 736, in save_tuple
save(element)
File "C:\Python36\lib\pickle.py", line 476, in save
f(self, obj) # Call unbound method with explicit self
File "C:\Users\lharris\PycharmProjects\road_condition_py3\venv\lib\site-packages\dill\_dill.py", line 1120, in save_cell
pickler.save_reduce(_create_cell, (f,), obj=obj)
File "C:\Python36\lib\pickle.py", line 610, in save_reduce
save(args)
File "C:\Python36\lib\pickle.py", line 476, in save
f(self, obj) # Call unbound method with explicit self
File "C:\Python36\lib\pickle.py", line 736, in save_tuple
save(element)
File "C:\Python36\lib\pickle.py", line 476, in save
f(self, obj) # Call unbound method with explicit self
File "C:\Users\lharris\PycharmProjects\road_condition_py3\venv\lib\site-packages\dill\_dill.py", line 1069, in save_instancemethod0
pickler.save_reduce(MethodType, (obj.__func__, obj.__self__), obj=obj)
File "C:\Python36\lib\pickle.py", line 610, in save_reduce
save(args)
File "C:\Python36\lib\pickle.py", line 476, in save
f(self, obj) # Call unbound method with explicit self
File "C:\Python36\lib\pickle.py", line 736, in save_tuple
save(element)
File "C:\Python36\lib\pickle.py", line 521, in save
self.save_reduce(obj=obj, *rv)
File "C:\Python36\lib\pickle.py", line 634, in save_reduce
save(state)
File "C:\Python36\lib\pickle.py", line 476, in save
f(self, obj) # Call unbound method with explicit self
File "C:\Users\lharris\PycharmProjects\road_condition_py3\venv\lib\site-packages\dill\_dill.py", line 893, in save_module_dict
StockPickler.save_dict(pickler, obj)
File "C:\Python36\lib\pickle.py", line 821, in save_dict
self._batch_setitems(obj.items())
File "C:\Python36\lib\pickle.py", line 852, in _batch_setitems
save(v)
File "C:\Python36\lib\pickle.py", line 521, in save
self.save_reduce(obj=obj, *rv)
File "C:\Python36\lib\pickle.py", line 634, in save_reduce
save(state)
File "C:\Python36\lib\pickle.py", line 476, in save
f(self, obj) # Call unbound method with explicit self
File "C:\Users\lharris\PycharmProjects\road_condition_py3\venv\lib\site-packages\dill\_dill.py", line 893, in save_module_dict
StockPickler.save_dict(pickler, obj)
File "C:\Python36\lib\pickle.py", line 821, in save_dict
self._batch_setitems(obj.items())
File "C:\Python36\lib\pickle.py", line 852, in _batch_setitems
save(v)
File "C:\Python36\lib\pickle.py", line 496, in save
rv = reduce(self.proto)
TypeError: can't pickle SwigPyObject objects
看了一下,看来Pathos是正确使用了Dill和Multiprocess。那么有没有一种方法可以并行处理SwigPyObjects,无论是使用Pathos还是其他方法?
几周前有人问过类似的问题,但没有得到任何答案(Python pathos错误,无法拾取SwigPyObject对象。),我问了一个相关的问题,之前我无法使用Pathos(如何在Python中使用copy_reg.pickle注册'SwigPyObject'类型?).
我在 Windows 7 中使用 Python 3.6.5 遇到了这个错误,在 PyCharm 中开发,使用的是一个虚拟环境,在这个虚拟环境中,我所需要的包都是从 PyPi 下载的 .whl 文件中 pip 安装的 (我无法在我的网络上正常使用 pip install)。
如果有人能给我任何帮助,我将非常高兴
因为 get_small_image
是一个绑定的方法,每个工人都需要一个副本的 class_obj
. 在多处理的情况下,这是通过传递腌制的python对象来实现的。然而,由于该对象包含了一个类的成员 SwigPyObject
class_obj
是不能被选中的,整个事情就失败了。
最直接的修复方法是这样的。
class MyClass:
def __init__(self, image):
self.image_object = None
self.image = image
def get_small_image(self, coord, size=100):
if self.image_object is None:
self.image_object = gdal.Open(self.image)
small_image = self.image_object.ReadAsArray(coord[0], coord[1], size, size)
return small_image
def run_multi(self, coords_in):
pool = pp.ProcessPool(2)
output = pool.map(self.get_small_image, coords_in)
return output
图片的懒惰加载会导致 SwigPyObject
有待建立 之后 对象已经被子进程pickledunpickled,从而避免了你遇到的问题。