小编Sou*_*nak的帖子

我有像这样的pandas DataFrame

        X    Y  Z    Value 
0      18   55  1      70   
1      18   55  2      67 
2      18   57  2      75     
3      18   58  1      35  
4      19   54  2      70   

我想以这种方式将这些数据写入文本文件,

18 55 1 70   
18 55 2 67 
18 57 2 75     
18 58 1 35  
19 54 2 70 

我尝试过类似的东西

f = open(writePath, 'a')
f.writelines(['\n', str(data['X']), ' ', str(data['Y']), ' ', str(data['Z']), ' ', str(data['Value'])])
f.close()

但它不起作用.这该怎么做？

我用CMake找到Boost.找到了Boost,但CMake出错了

导入的目标不适用于Boost版本

请参阅下面的完整错误(来自macOS).我究竟做错了什么？

CMake Warning at /Applications/CMake.app/Contents/share/cmake-3.6/Modules/FindBoost.cmake:743 (message):
  Imported targets not available for Boost version 106300
Call Stack (most recent call first):
  /Applications/CMake.app/Contents/share/cmake-3.6/Modules/FindBoost.cmake:842 (_Boost_COMPONENT_DEPENDENCIES)
/Applications/CMake.app/Contents/share/cmake-3.6/Modules/FindBoost.cmake:1395 (_Boost_MISSING_DEPENDENCIES)
CMakeLists.txt:6 (find_package)

Boost version: 1.63.0
Found the following Boost libraries:
  thread
CMake Warning at /Applications/CMake.app/Contents/share/cmake-3.6/Modules/FindBoost.cmake:743 (message):
  Imported targets not available for Boost version 106300
Call Stack (most recent call first):
  /Applications/CMake.app/Contents/share/cmake-3.6/Modules/FindBoost.cmake:842 (_Boost_COMPONENT_DEPENDENCIES)
  /Applications/CMake.app/Contents/share/cmake-3.6/Modules/FindBoost.cmake:1395 (_Boost_MISSING_DEPENDENCIES)
  CMakeLists.txt:7 (find_package)

我想从形状点创建一个多边形.

from shapely import geometry
p1 = geometry.Point(0,0)
p2 = geometry.Point(1,0)
p3 = geometry.Point(1,1)
p4 = geometry.Point(0,1)

pointList = [p1, p2, p3, p4, p1]

poly = geometry.Polygon(pointList)

给我一个类型错误 TypeError: object of type 'Point' has no len()

如何Polygon从形状Point对象中创建？

什么是效用out参数在某些numpy功能,如cumsum或cumprod或其他数学函数？

如果结果很大,是否有助于使用该out参数来提高计算时间或内存效率？

该线程提供了有关如何使用它的一些信息.但我想知道我什么时候应该使用它,有什么好处呢？

在系列文档中,使用参数name和fastpath未解释.他们在做什么？

有没有办法将数组存储在hdf5文件中,这个文件太大而无法在内存中加载？

如果我做这样的事情

f = h5py.File('test.hdf5','w')
f['mydata'] = np.zeros(2**32)

我收到内存错误.

我按照README中的OpenNI安装指南https://github.com/OpenNI/OpenNI.我也安装了libtool和libusb.但是,当我./RedistMaker在Platform/Linux-x86/CreateRedist下运行时,我收到了这样的错误消息:

PrimeSense OpenNI Redist * 
2011-10-12 23:18:46 * ********************************* 
Taking version... version is 1.3.3.6 
Building OpenNI... In file included from ../../../../Source/OpenNI/ 
XnDump.cpp:25: ../../../../Include/XnDump.h:167: warning: ‘warning’ 
attribute directive ignored ../../../../Include/XnDump.h:168: warning: 
‘warning’ attribute directive ignored ../../../../Include/XnDump.h: 
169: warning: ‘warning’ attribute directive ignored ../../../../ 
Include/XnDump.h:170: warning: ‘warning’ attribute directive 
ignored ../../../../Include/XnDump.h:171: warning: ‘warning’ attribute 
directive ignored ../../../../Include/XnDump.h:172: warning: ‘warning’ 
attribute directive ignored In file included from ../../../../Source/ 
OpenNI/XnDump.cpp:25: ../../../../Include/XnDump.h:167: warning: 
‘warning’ attribute directive ignored ../../../../Include/XnDump.h: 
168: warning: ‘warning’ …

Docstring说:

Polygon.contains 如果几何包含另一个,则返回True,否则返回False

Polygon.within 如果几何在另一个内,则返回True,否则返回False

他们有什么不同？

a
Out[57]: 
array([[1, 2],
       [3, 4]])

b
Out[58]: 
 array([[5, 6],
       [7, 8]])

In[63]: a[:,-1] + b
Out[63]: 
array([[ 7, 10],
       [ 9, 12]])

这是行添加.如何将列添加到列中以获取

In [65]: result
Out[65]: 
array([[ 7,  8],
       [11, 12]])

我不想转置整个数组,添加然后转置回来.还有其他方法吗？

import time
from multiprocessing import Process

def loop(limit):
    for i in xrange(limit):
        pass
    print i

limit = 100000000 #100 million

start = time.time()    

for i in xrange(5):
    p = Process(target=loop, args=(limit,))
    p.start()
p.join()

end = time.time()
print end - start

我尝试运行此代码，这是我得到的输出

99999999
99999999
2.73401999474
99999999
99999999
99999999

而有时

99999999
99999999
3.72434902191
99999999
99999999
99999999
99999999
99999999

在这种情况下，循环函数被调用了 7 次而不是 5 次。为什么会有这种奇怪的行为？

我也对p.join()声明的作用感到困惑。它是同时结束任何一个进程还是所有进程？

import h5py
import numpy as np

f = h5py.File('test','w')
f.create_dataset('key1', data = np.array([1,2,3]))
f.create_dataset('key2', data = np.array([4,5,6]))
f.close()

创建名为 test 的文件，并分别在 key1 和 key2 下写入两个数组。

但是，关闭文件对象并重新打开文件会删除以前存储的数据。

f = h5py.File('test','w')
f.create_dataset('key1', data = np.array([1,2,3]))
f.close()
f = h5py.File('test','w')
f.create_dataset('key2', data = np.array([4,5,6]))
f.close()

在这种情况下，仅[4,5,6]存储在 key 下key2。

如何重新打开文件并写入新数据而不删除已存储的旧数据？

这是一个图像示例。图像中的对象似乎已旋转。我如何撤消它的旋转？