cv2 distanceTransform函数的用法 python

python李魔佛 发表了文章 • 0 个评论 • 3467 次浏览 • 2019-07-08 15:35 • 来自相关话题

distanceTransform
Calculates the distance to the closest zero pixel for each pixel of the source image.


Python: cv2.distanceTransform(src, distanceType, maskSize[, dst]) → dst

Python: cv.DistTransform(src, dst, distance_type=CV_DIST_L2, mask_size=3, mask=None, labels=None) → None
Parameters:
src – 8-bit, single-channel (binary) source image.
dst – Output image with calculated distances. It is a 32-bit floating-point, single-channel image of the same size as src .
distanceType – Type of distance. It can be CV_DIST_L1, CV_DIST_L2 , or CV_DIST_C .
maskSize – Size of the distance transform mask. It can be 3, 5, or CV_DIST_MASK_PRECISE (the latter option is only supported by the first function). In case of the CV_DIST_L1 or CV_DIST_C distance type, the parameter is forced to 3 because a 3\times 3 mask gives the same result as 5\times 5 or any larger aperture.
labels – Optional output 2D array of labels (the discrete Voronoi diagram). It has the type CV_32SC1 and the same size as src . See the details below.
labelType – Type of the label array to build. If labelType==DIST_LABEL_CCOMP then each connected component of zeros in src (as well as all the non-zero pixels closest to the connected component) will be assigned the same label. If labelType==DIST_LABEL_PIXEL then each zero pixel (and all the non-zero pixels closest to it) gets its own label.
The functions distanceTransform calculate the approximate or precise distance from every binary image pixel to the nearest zero pixel. For zero image pixels, the distance will obviously be zero.


When maskSize == CV_DIST_MASK_PRECISE and distanceType == CV_DIST_L2 , the function runs the algorithm described in [Felzenszwalb04]. This algorithm is parallelized with the TBB library.

In other cases, the algorithm [Borgefors86] is used. This means that for a pixel the function finds the shortest path to the nearest zero pixel consisting of basic shifts: horizontal, vertical, diagonal, or knight’s move (the latest is available for a 5\times 5 mask). The overall distance is calculated as a sum of these basic distances. Since the distance function should be symmetric, all of the horizontal and vertical shifts must have the same cost (denoted as a ), all the diagonal shifts must have the same cost (denoted as b ), and all knight’s moves must have the same cost (denoted as c ). For the CV_DIST_C and CV_DIST_L1 types, the distance is calculated precisely, whereas for CV_DIST_L2 (Euclidean distance) the distance can be calculated only with a relative error (a 5\times 5 mask gives more accurate results). For a,``b`` , and c , OpenCV uses the values suggested in the original paper:

CV_DIST_C (3\times 3) a = 1, b = 1
CV_DIST_L1 (3\times 3) a = 1, b = 2
CV_DIST_L2 (3\times 3) a=0.955, b=1.3693
CV_DIST_L2 (5\times 5) a=1, b=1.4, c=2.1969
Typically, for a fast, coarse distance estimation CV_DIST_L2, a 3\times 3 mask is used. For a more accurate distance estimation CV_DIST_L2 , a 5\times 5 mask or the precise algorithm is used. Note that both the precise and the approximate algorithms are linear on the number of pixels.

The second variant of the function does not only compute the minimum distance for each pixel (x, y) but also identifies the nearest connected component consisting of zero pixels (labelType==DIST_LABEL_CCOMP) or the nearest zero pixel (labelType==DIST_LABEL_PIXEL). Index of the component/pixel is stored in \texttt{labels}(x, y) . When labelType==DIST_LABEL_CCOMP, the function automatically finds connected components of zero pixels in the input image and marks them with distinct labels. When labelType==DIST_LABEL_CCOMP, the function scans through the input image and marks all the zero pixels with distinct labels.

In this mode, the complexity is still linear. That is, the function provides a very fast way to compute the Voronoi diagram for a binary image. Currently, the second variant can use only the approximate distance transform algorithm, i.e. maskSize=CV_DIST_MASK_PRECISE is not supported yet.

Note
An example on using the distance transform can be found at opencv_source_code/samples/cpp/distrans.cpp
(Python) An example on using the distance transform can be found at opencv_source/samples/python2/distrans.py 

  查看全部
distanceTransform
Calculates the distance to the closest zero pixel for each pixel of the source image.


Python: cv2.distanceTransform(src, distanceType, maskSize[, dst]) → dst

Python: cv.DistTransform(src, dst, distance_type=CV_DIST_L2, mask_size=3, mask=None, labels=None) → None

Parameters:
src – 8-bit, single-channel (binary) source image.
dst – Output image with calculated distances. It is a 32-bit floating-point, single-channel image of the same size as src .

distanceType – Type of distance. It can be CV_DIST_L1, CV_DIST_L2 , or CV_DIST_C .
maskSize – Size of the distance transform mask. It can be 3, 5, or CV_DIST_MASK_PRECISE (the latter option is only supported by the first function). In case of the CV_DIST_L1 or CV_DIST_C distance type, the parameter is forced to 3 because a 3\times 3 mask gives the same result as 5\times 5 or any larger aperture.

labels – Optional output 2D array of labels (the discrete Voronoi diagram). It has the type CV_32SC1 and the same size as src . See the details below.

labelType – Type of the label array to build. If labelType==DIST_LABEL_CCOMP then each connected component of zeros in src (as well as all the non-zero pixels closest to the connected component) will be assigned the same label. If labelType==DIST_LABEL_PIXEL then each zero pixel (and all the non-zero pixels closest to it) gets its own label.
The functions distanceTransform calculate the approximate or precise distance from every binary image pixel to the nearest zero pixel. For zero image pixels, the distance will obviously be zero.


When maskSize == CV_DIST_MASK_PRECISE and distanceType == CV_DIST_L2 , the function runs the algorithm described in [Felzenszwalb04]. This algorithm is parallelized with the TBB library.

In other cases, the algorithm [Borgefors86] is used. This means that for a pixel the function finds the shortest path to the nearest zero pixel consisting of basic shifts: horizontal, vertical, diagonal, or knight’s move (the latest is available for a 5\times 5 mask). The overall distance is calculated as a sum of these basic distances. Since the distance function should be symmetric, all of the horizontal and vertical shifts must have the same cost (denoted as a ), all the diagonal shifts must have the same cost (denoted as b ), and all knight’s moves must have the same cost (denoted as c ). For the CV_DIST_C and CV_DIST_L1 types, the distance is calculated precisely, whereas for CV_DIST_L2 (Euclidean distance) the distance can be calculated only with a relative error (a 5\times 5 mask gives more accurate results). For a,``b`` , and c , OpenCV uses the values suggested in the original paper:

CV_DIST_C (3\times 3) a = 1, b = 1
CV_DIST_L1 (3\times 3) a = 1, b = 2
CV_DIST_L2 (3\times 3) a=0.955, b=1.3693
CV_DIST_L2 (5\times 5) a=1, b=1.4, c=2.1969
Typically, for a fast, coarse distance estimation CV_DIST_L2, a 3\times 3 mask is used. For a more accurate distance estimation CV_DIST_L2 , a 5\times 5 mask or the precise algorithm is used. Note that both the precise and the approximate algorithms are linear on the number of pixels.

The second variant of the function does not only compute the minimum distance for each pixel (x, y) but also identifies the nearest connected component consisting of zero pixels (labelType==DIST_LABEL_CCOMP) or the nearest zero pixel (labelType==DIST_LABEL_PIXEL). Index of the component/pixel is stored in \texttt{labels}(x, y) . When labelType==DIST_LABEL_CCOMP, the function automatically finds connected components of zero pixels in the input image and marks them with distinct labels. When labelType==DIST_LABEL_CCOMP, the function scans through the input image and marks all the zero pixels with distinct labels.

In this mode, the complexity is still linear. That is, the function provides a very fast way to compute the Voronoi diagram for a binary image. Currently, the second variant can use only the approximate distance transform algorithm, i.e. maskSize=CV_DIST_MASK_PRECISE is not supported yet.

Note
An example on using the distance transform can be found at opencv_source_code/samples/cpp/distrans.cpp
(Python) An example on using the distance transform can be found at opencv_source/samples/python2/distrans.py
 

 

Django 版本不兼容报错 AuthenticationMiddleware

数据库李魔佛 发表了文章 • 0 个评论 • 2698 次浏览 • 2019-07-04 15:43 • 来自相关话题

Django 2.2.ERRORS:
?: (admin.E408) 'django.contrib.auth.middleware.AuthenticationMiddleware' must be in MIDDLEWARE in order to use the admin application. 
在之前的版本上没有问题,更新后就出错。
降级Django
 
pip install django=2.1.7
 
PS: 这个django的版本兼容的确是个大问题,哪天升级了下django版本,不经过严格的测试就带来灾难性的后果。 查看全部
Django 2.2.
ERRORS:
?: (admin.E408) 'django.contrib.auth.middleware.AuthenticationMiddleware' must be in MIDDLEWARE in order to use the admin application.
 
在之前的版本上没有问题,更新后就出错。
降级Django
 
pip install django=2.1.7
 
PS: 这个django的版本兼容的确是个大问题,哪天升级了下django版本,不经过严格的测试就带来灾难性的后果。

Win10下PhantomJS无法运行 【版本兼容问题】

python李魔佛 发表了文章 • 0 个评论 • 1636 次浏览 • 2019-07-04 09:07 • 来自相关话题

以前在win7上运行的好好的。
在win10下就报错:
selenium.common.exceptions.WebDriverException: Message: Service C:\Tool\phantomjs-2.5.0-beta2-windows\phantomjs-2.5.0-beta2-windows\bin\phantomjs.exe unexpectedly exited. Status code was: 4294967295
 
后来替换了一个旧的版本,发现问题就这么解决了。
旧版本:phantomjs-2.1.1-windows
 
原创文章
转载请注明出处 
http://30daydo.com/article/505
  查看全部
以前在win7上运行的好好的。
在win10下就报错:
selenium.common.exceptions.WebDriverException: Message: Service C:\Tool\phantomjs-2.5.0-beta2-windows\phantomjs-2.5.0-beta2-windows\bin\phantomjs.exe unexpectedly exited. Status code was: 4294967295
 
后来替换了一个旧的版本,发现问题就这么解决了。
旧版本:phantomjs-2.1.1-windows
 
原创文章
转载请注明出处 
http://30daydo.com/article/505
 

nunpy中的std标准差是样本差吗

量化交易李魔佛 发表了文章 • 0 个评论 • 767 次浏览 • 2019-07-01 10:08 • 来自相关话题

写个代码测试下:
# 测试一下那个方差
x=[1,2,3,4,5,6,7,8,9,10]
X = np.array(x)
X.mean()
5.5
 
X.std() # 标准差
2.8722813232690143
 
手工计算一下:
def my_fangca(X):
l=len(X)
mean=X.mean()
sum_ = 0
sum_std=0
for i in X:
sum_+=(i-mean)**2
var_=sum_/l
std_=(sum_/(l))**0.5
return var_,std_
result = my_fangca(X)
得到的result

(8.25, 2.8722813232690143)
 
说明numpy的std是标准差,不是样本差 查看全部
写个代码测试下:
# 测试一下那个方差
x=[1,2,3,4,5,6,7,8,9,10]
X = np.array(x)
X.mean()
5.5
 
X.std() # 标准差
2.8722813232690143
 
手工计算一下:
def my_fangca(X):
l=len(X)
mean=X.mean()
sum_ = 0
sum_std=0
for i in X:
sum_+=(i-mean)**2
var_=sum_/l
std_=(sum_/(l))**0.5
return var_,std_

result = my_fangca(X)
得到的result

(8.25, 2.8722813232690143)
 
说明numpy的std是标准差,不是样本差

喜马拉雅app 爬取音频文件

python爬虫李魔佛 发表了文章 • 0 个评论 • 2402 次浏览 • 2019-06-30 12:24 • 来自相关话题

============== 2019-10-28更新 =================
因为喜马拉雅的源码格式改了,所以爬虫代码也更新了一波
# -*- coding: utf-8 -*-
# website: http://30daydo.com
# @Time : 2019/6/30 12:03
# @File : main.py

import requests
import re
import os

url = 'http://180.153.255.6/mobile/v1/album/track/ts-1571294887744?albumId=23057324&device=android&isAsc=true&isQueryInvitationBrand=true&pageId={}&pageSize=20&pre_page=0'
headers = {'User-Agent': 'Xiaomi'}

def download():
for i in range(1, 3):
r = requests.get(url=url.format(i), headers=headers)
js_data = r.json()
data_list = js_data.get('data', {}).get('list', [])
for item in data_list:
trackName = item.get('title')
trackName = re.sub('[\/\\\:\*\?\"\<\>\|]', '_', trackName)
# trackName=re.sub(':','',trackName)
src_url = item.get('playUrl64')
filename = '{}.mp3'.format(trackName)
if not os.path.exists(filename):

try:
r0 = requests.get(src_url, headers=headers)
except Exception as e:
print(e)
print(trackName)
r0 = requests.get(src_url, headers=headers)


else:
with open(filename, 'wb') as f:
f.write(r0.content)

print('{} downloaded'.format(trackName))

else:
print(f'{filename}已经下载过了')

import shutil

def rename_():
for i in range(1, 3):
r = requests.get(url=url.format(i), headers=headers)
js_data = r.json()
data_list = js_data.get('data', {}).get('list', [])
for item in data_list:
trackName = item.get('title')
trackName = re.sub('[\/\\\:\*\?\"\<\>\|]', '_', trackName)
src_url = item.get('playUrl64')

orderNo=item.get('orderNo')

filename = '{}.mp3'.format(trackName)
try:

if os.path.exists(filename):
new_file='{}_{}.mp3'.format(orderNo,trackName)
shutil.move(filename,new_file)
except Exception as e:
print(e)





if __name__=='__main__':
rename_()
 
音频文件也更新了,详情见百度网盘。
 
 
======== 2018-10=============
 爬取喜马拉雅app上 杨继东的投资之道 的音频文件
运行环境:python3# -*- coding: utf-8 -*-
# website: http://30daydo.com
# @Time : 2019/6/30 12:03
# @File : main.py

import requests
import re
url = 'https://www.ximalaya.com/revision/play/album?albumId=23057324&pageNum=1&sort=1&pageSize=60'
headers={'User-Agent':'Xiaomi'}

r = requests.get(url=url,headers=headers)
js_data = r.json()
data_list = js_data.get('data',{}).get('tracksAudioPlay',)
for item in data_list:
trackName=item.get('trackName')
trackName=re.sub(':','',trackName)
src_url = item.get('src')
try:
r0=requests.get(src_url,headers=headers)
except Exception as e:
print(e)
print(trackName)
else:
with open('{}.m4a'.format(trackName),'wb') as f:
f.write(r0.content)
print('{} downloaded'.format(trackName))
保存为main.py
然后运行 python main.py
稍微等几分钟就自动下载好了。







附下载好的音频文件:
链接:https://pan.baidu.com/s/1t_vJhTvSJSeFdI1IaDS6fA 
提取码:e3zb 
 

原创文章
转载请注明出处
http://30daydo.com/article/503 查看全部
============== 2019-10-28更新 =================
因为喜马拉雅的源码格式改了,所以爬虫代码也更新了一波
# -*- coding: utf-8 -*-
# website: http://30daydo.com
# @Time : 2019/6/30 12:03
# @File : main.py

import requests
import re
import os

url = 'http://180.153.255.6/mobile/v1/album/track/ts-1571294887744?albumId=23057324&device=android&isAsc=true&isQueryInvitationBrand=true&pageId={}&pageSize=20&pre_page=0'
headers = {'User-Agent': 'Xiaomi'}

def download():
for i in range(1, 3):
r = requests.get(url=url.format(i), headers=headers)
js_data = r.json()
data_list = js_data.get('data', {}).get('list', [])
for item in data_list:
trackName = item.get('title')
trackName = re.sub('[\/\\\:\*\?\"\<\>\|]', '_', trackName)
# trackName=re.sub(':','',trackName)
src_url = item.get('playUrl64')
filename = '{}.mp3'.format(trackName)
if not os.path.exists(filename):

try:
r0 = requests.get(src_url, headers=headers)
except Exception as e:
print(e)
print(trackName)
r0 = requests.get(src_url, headers=headers)


else:
with open(filename, 'wb') as f:
f.write(r0.content)

print('{} downloaded'.format(trackName))

else:
print(f'{filename}已经下载过了')

import shutil

def rename_():
for i in range(1, 3):
r = requests.get(url=url.format(i), headers=headers)
js_data = r.json()
data_list = js_data.get('data', {}).get('list', [])
for item in data_list:
trackName = item.get('title')
trackName = re.sub('[\/\\\:\*\?\"\<\>\|]', '_', trackName)
src_url = item.get('playUrl64')

orderNo=item.get('orderNo')

filename = '{}.mp3'.format(trackName)
try:

if os.path.exists(filename):
new_file='{}_{}.mp3'.format(orderNo,trackName)
shutil.move(filename,new_file)
except Exception as e:
print(e)





if __name__=='__main__':
rename_()

 
音频文件也更新了,详情见百度网盘。
 
 
======== 2018-10=============
 爬取喜马拉雅app上 杨继东的投资之道 的音频文件
运行环境:python3
# -*- coding: utf-8 -*-
# website: http://30daydo.com
# @Time : 2019/6/30 12:03
# @File : main.py

import requests
import re
url = 'https://www.ximalaya.com/revision/play/album?albumId=23057324&pageNum=1&sort=1&pageSize=60'
headers={'User-Agent':'Xiaomi'}

r = requests.get(url=url,headers=headers)
js_data = r.json()
data_list = js_data.get('data',{}).get('tracksAudioPlay',)
for item in data_list:
trackName=item.get('trackName')
trackName=re.sub(':','',trackName)
src_url = item.get('src')
try:
r0=requests.get(src_url,headers=headers)
except Exception as e:
print(e)
print(trackName)
else:
with open('{}.m4a'.format(trackName),'wb') as f:
f.write(r0.content)
print('{} downloaded'.format(trackName))

保存为main.py
然后运行 python main.py
稍微等几分钟就自动下载好了。


喜马拉雅.PNG


附下载好的音频文件:
链接:https://pan.baidu.com/s/1t_vJhTvSJSeFdI1IaDS6fA 
提取码:e3zb 
 

原创文章
转载请注明出处
http://30daydo.com/article/503

python3与python2迭代器的写法的区别

python李魔佛 发表了文章 • 0 个评论 • 628 次浏览 • 2019-06-26 11:22 • 来自相关话题

大部分相同,只是python2里面需要实现在类中实现next()方法,而python3里面需要实现__next__()方法。
 
附一个例子:
def iter_demo():

class DefineIter(object):

def __init__(self,length):
self.length = length
self.data = range(self.length)
self.index=0

def __iter__(self):
return self


def __next__(self):

if self.index >=self.length:
# return None
raise StopIteration

d = self.data[self.index]*50
self.index =self.index + 1

return d

a = DefineIter(10)
print(type(a))
for i in a:
print(i) 查看全部
大部分相同,只是python2里面需要实现在类中实现next()方法,而python3里面需要实现__next__()方法。
 
附一个例子:
def iter_demo():

class DefineIter(object):

def __init__(self,length):
self.length = length
self.data = range(self.length)
self.index=0

def __iter__(self):
return self


def __next__(self):

if self.index >=self.length:
# return None
raise StopIteration

d = self.data[self.index]*50
self.index =self.index + 1

return d

a = DefineIter(10)
print(type(a))
for i in a:
print(i)

PyCharm 快捷键快速插入当前时间

python李魔佛 发表了文章 • 0 个评论 • 843 次浏览 • 2019-06-26 09:18 • 来自相关话题

个人觉得这是一个非常常用的功能,不过需要自定义实现。
 
方式
通过 Live Template 快速添加时间

步骤
1、添加一个 Template Group 命名为 Common
2、添加一个 Live Template 设置如下
Abbreviation: time
Description : current time
Template Text: $time$

Edit Variables -> Expresssion : date("yyyy-MM-dd HH:mm:ss")



3、让设置生效
Define->Everywhere

4、使用
输入 time 后 按下tab键 就能转换为当前时间了
  查看全部
个人觉得这是一个非常常用的功能,不过需要自定义实现。
 
方式
通过 Live Template 快速添加时间

步骤
1、添加一个 Template Group 命名为 Common
2、添加一个 Live Template 设置如下
Abbreviation: time
Description : current time
Template Text: $time$

Edit Variables -> Expresssion : date("yyyy-MM-dd HH:mm:ss")



3、让设置生效
Define->Everywhere

4、使用
输入 time 后 按下tab键 就能转换为当前时间了

 

深圳转债转股后不可以撤单

股票李魔佛 发表了文章 • 0 个评论 • 657 次浏览 • 2019-06-25 09:12 • 来自相关话题

亲身经历,深圳转债转股后可以撤单操作,并显示已撤单,但是晚上正常转股了。
说明转股后也是不能撤单的。
亲身经历,深圳转债转股后可以撤单操作,并显示已撤单,但是晚上正常转股了。
说明转股后也是不能撤单的。

有用tushare做实盘交易的大神吗?现在buy和sell都无法委托下单了怎么回事?

股票aka_12 回复了问题 • 2 人关注 • 2 个回复 • 1317 次浏览 • 2019-06-17 14:29 • 来自相关话题

修改easytrader国金证券的默认启动路径

量化交易李魔佛 发表了文章 • 0 个评论 • 955 次浏览 • 2019-06-17 10:23 • 来自相关话题

如果你的国金证券不是安装在默认路径的话,会无法启动。报错:

pywinauto.application.AppStartError: Could not create the process "C:\全能行证券交易终端\xiadan.exe"
Error returned by CreateProcess: (2, 'CreateProcess', '系统找不到指定的文件。')

 
看了配置文件,也是没有具体的参数可以修改,只好修改源代码。
别听到改源代码就害怕,只是需要改一行就可以了。
 
找到文件:
site-package\easytrader\config\client.py
 
找过这一行:
class GJ(CommonConfig):
DEFAULT_EXE_PATH = "C:\\Tool\\xiadan.exe"只要修改上面的路径就可以了。注意用双斜杠。
  查看全部
如果你的国金证券不是安装在默认路径的话,会无法启动。报错:


pywinauto.application.AppStartError: Could not create the process "C:\全能行证券交易终端\xiadan.exe"
Error returned by CreateProcess: (2, 'CreateProcess', '系统找不到指定的文件。')


 
看了配置文件,也是没有具体的参数可以修改,只好修改源代码。
别听到改源代码就害怕,只是需要改一行就可以了。
 
找到文件:
site-package\easytrader\config\client.py
 
找过这一行:
class GJ(CommonConfig):
DEFAULT_EXE_PATH = "C:\\Tool\\xiadan.exe"
只要修改上面的路径就可以了。注意用双斜杠。
 

conda无法在win10下用命令行切换虚拟环境

python李魔佛 发表了文章 • 0 个评论 • 1258 次浏览 • 2019-06-11 10:04 • 来自相关话题

虚拟环境已经安装好了
然后在PowerShell下运行activate py2,没有任何反应。(powershell是win7后面系统的增强命令行)
后来使用系统原始的cmd命令行,在运行里面敲入cmd,然后重新执行activate py2,问题得到解决了。
原因是兼容问题。 查看全部
虚拟环境已经安装好了
然后在PowerShell下运行activate py2,没有任何反应。(powershell是win7后面系统的增强命令行)
后来使用系统原始的cmd命令行,在运行里面敲入cmd,然后重新执行activate py2,问题得到解决了。
原因是兼容问题。

使用pymongo中的find_one_and_update出错:需要分片键

数据库李魔佛 发表了文章 • 0 个评论 • 1135 次浏览 • 2019-06-10 17:13 • 来自相关话题

错误信息如下: File "C:\ProgramData\Anaconda3\lib\site-packages\pymongo\helpers.py", line 155, in _check_command_response
raise OperationFailure(msg % errmsg, code, response)
pymongo.errors.OperationFailure: Query for sharded findAndModify must contain the shard key
2019-06-10 16:14:32 [scrapy.core.engine] INFO: Closing spider (finished)
2019-06-10 16:14:32 [scrapy.statscollectors] INFO: Dumping Scrapy stats:
需要在查询语句中把分片键也添加进去。
因为findOneModify只会找一个记录,但是到底在哪个分片的记录呢? 因为不确定,所以才需要把shard加上去。
 
 
参考官方:
Targeted Operations vs. Broadcast Operations
Generally, the fastest queries in a sharded environment are those that mongos route to a single shard, using the shard key and the cluster meta data from the config server. These targeted operations use the shard key value to locate the shard or subset of shards that satisfy the query document.
For queries that don’t include the shard key, mongos must query all shards, wait for their responses and then return the result to the application. These “scatter/gather” queries can be long running operations.
Broadcast Operations
mongos instances broadcast queries to all shards for the collection unless the mongos can determine which shard or subset of shards stores this data.

After the mongos receives responses from all shards, it merges the data and returns the result document. The performance of a broadcast operation depends on the overall load of the cluster, as well as variables like network latency, individual shard load, and number of documents returned per shard. Whenever possible, favor operations that result in targeted operation over those that result in a broadcast operation.
Multi-update operations are always broadcast operations.
The updateMany() and deleteMany() methods are broadcast operations, unless the query document specifies the shard key in full.
Targeted Operations
mongos can route queries that include the shard key or the prefix of a compound shard key a specific shard or set of shards. mongos uses the shard key value to locate the chunk whose range includes the shard key value and directs the query at the shard containing that chunk.

For example, if the shard key is:
copy
{ a: 1, b: 1, c: 1 }

The mongos program can route queries that include the full shard key or either of the following shard key prefixes at a specific shard or set of shards:
copy
{ a: 1 }
{ a: 1, b: 1 }

All insertOne() operations target to one shard. Each document in the insertMany() array targets to a single shard, but there is no guarantee all documents in the array insert into a single shard.
All updateOne(), replaceOne() and deleteOne() operations must include the shard key or _id in the query document. MongoDB returns an error if these methods are used without the shard key or _id.
Depending on the distribution of data in the cluster and the selectivity of the query, mongos may still perform a broadcast operation to fulfill these queries.
Index Use
If the query does not include the shard key, the mongos must send the query to all shards as a “scatter/gather” operation. Each shard will, in turn, use either the shard key index or another more efficient index to fulfill the query.
If the query includes multiple sub-expressions that reference the fields indexed by the shard key and the secondary index, the mongos can route the queries to a specific shard and the shard will use the index that will allow it to fulfill most efficiently.
Sharded Cluster Security
Use Internal Authentication to enforce intra-cluster security and prevent unauthorized cluster components from accessing the cluster. You must start each mongod or mongos in the cluster with the appropriate security settings in order to enforce internal authentication.
See Deploy Sharded Cluster with Keyfile Access Control for a tutorial on deploying a secured shardedcluster.
Cluster Users
Sharded clusters support Role-Based Access Control (RBAC) for restricting unauthorized access to cluster data and operations. You must start each mongod in the cluster, including the config servers, with the --auth option in order to enforce RBAC. Alternatively, enforcing Internal Authentication for inter-cluster security also enables user access controls via RBAC.
With RBAC enforced, clients must specify a --username, --password, and --authenticationDatabase when connecting to the mongos in order to access cluster resources.
Each cluster has its own cluster users. These users cannot be used to access individual shards.
See Enable Access Control for a tutorial on enabling adding users to an RBAC-enabled MongoDB deployment. 查看全部
错误信息如下:
  File "C:\ProgramData\Anaconda3\lib\site-packages\pymongo\helpers.py", line 155, in _check_command_response
raise OperationFailure(msg % errmsg, code, response)
pymongo.errors.OperationFailure: Query for sharded findAndModify must contain the shard key
2019-06-10 16:14:32 [scrapy.core.engine] INFO: Closing spider (finished)
2019-06-10 16:14:32 [scrapy.statscollectors] INFO: Dumping Scrapy stats:

需要在查询语句中把分片键也添加进去。
因为findOneModify只会找一个记录,但是到底在哪个分片的记录呢? 因为不确定,所以才需要把shard加上去。
 
 
参考官方:
Targeted Operations vs. Broadcast Operations
Generally, the fastest queries in a sharded environment are those that mongos route to a single shard, using the shard key and the cluster meta data from the config server. These targeted operations use the shard key value to locate the shard or subset of shards that satisfy the query document.
For queries that don’t include the shard key, mongos must query all shards, wait for their responses and then return the result to the application. These “scatter/gather” queries can be long running operations.
Broadcast Operations
mongos instances broadcast queries to all shards for the collection unless the mongos can determine which shard or subset of shards stores this data.

After the mongos receives responses from all shards, it merges the data and returns the result document. The performance of a broadcast operation depends on the overall load of the cluster, as well as variables like network latency, individual shard load, and number of documents returned per shard. Whenever possible, favor operations that result in targeted operation over those that result in a broadcast operation.
Multi-update operations are always broadcast operations.
The updateMany() and deleteMany() methods are broadcast operations, unless the query document specifies the shard key in full.
Targeted Operations
mongos can route queries that include the shard key or the prefix of a compound shard key a specific shard or set of shards. mongos uses the shard key value to locate the chunk whose range includes the shard key value and directs the query at the shard containing that chunk.

For example, if the shard key is:
copy
{ a: 1, b: 1, c: 1 }

The mongos program can route queries that include the full shard key or either of the following shard key prefixes at a specific shard or set of shards:
copy
{ a: 1 }
{ a: 1, b: 1 }

All insertOne() operations target to one shard. Each document in the insertMany() array targets to a single shard, but there is no guarantee all documents in the array insert into a single shard.
All updateOne(), replaceOne() and deleteOne() operations must include the shard key or _id in the query document. MongoDB returns an error if these methods are used without the shard key or _id.
Depending on the distribution of data in the cluster and the selectivity of the query, mongos may still perform a broadcast operation to fulfill these queries.
Index Use
If the query does not include the shard key, the mongos must send the query to all shards as a “scatter/gather” operation. Each shard will, in turn, use either the shard key index or another more efficient index to fulfill the query.
If the query includes multiple sub-expressions that reference the fields indexed by the shard key and the secondary index, the mongos can route the queries to a specific shard and the shard will use the index that will allow it to fulfill most efficiently.
Sharded Cluster Security
Use Internal Authentication to enforce intra-cluster security and prevent unauthorized cluster components from accessing the cluster. You must start each mongod or mongos in the cluster with the appropriate security settings in order to enforce internal authentication.
See Deploy Sharded Cluster with Keyfile Access Control for a tutorial on deploying a secured shardedcluster.
Cluster Users
Sharded clusters support Role-Based Access Control (RBAC) for restricting unauthorized access to cluster data and operations. You must start each mongod in the cluster, including the config servers, with the --auth option in order to enforce RBAC. Alternatively, enforcing Internal Authentication for inter-cluster security also enables user access controls via RBAC.
With RBAC enforced, clients must specify a --username, --password, and --authenticationDatabase when connecting to the mongos in order to access cluster resources.
Each cluster has its own cluster users. These users cannot be used to access individual shards.
See Enable Access Control for a tutorial on enabling adding users to an RBAC-enabled MongoDB deployment.

jupyter notebook格式的文件损坏如何修复

python李魔佛 发表了文章 • 0 个评论 • 994 次浏览 • 2019-06-08 13:44 • 来自相关话题

有时候用git同步时,造成了冲突后合并,jupyter notebook的文件被插入了诸如>>>>>HEAD,ORIGIN等字符,这时候再打开jupyter notebook文件(.ipynb后缀),会无法打开。修复过程:
 
使用下面的代码:
# 拯救损坏的jupyter 文件
import re
import codecs

pattern = re.compile('"source": \[(.*?)\]\s+\},',re.S)
filename = 'tushare_usage.ipynb'
with codecs.open(filename,encoding='utf8') as f:
content = f.read()

source = pattern.findall(content)
for s in source:
t=s.replace('\\n','')
t=re.sub('"','',t)
t=re.sub('(,$)','',t)
print(t)只要把你要修复的文件替换一下就可以了。 查看全部
有时候用git同步时,造成了冲突后合并,jupyter notebook的文件被插入了诸如>>>>>HEAD,ORIGIN等字符,这时候再打开jupyter notebook文件(.ipynb后缀),会无法打开。修复过程:
 
使用下面的代码:
# 拯救损坏的jupyter 文件
import re
import codecs

pattern = re.compile('"source": \[(.*?)\]\s+\},',re.S)
filename = 'tushare_usage.ipynb'
with codecs.open(filename,encoding='utf8') as f:
content = f.read()

source = pattern.findall(content)
for s in source:
t=s.replace('\\n','')
t=re.sub('"','',t)
t=re.sub('(,$)','',t)
print(t)
只要把你要修复的文件替换一下就可以了。

Warning: unable to run listCollections, attempting to approximate collection

数据库李魔佛 发表了文章 • 0 个评论 • 4487 次浏览 • 2019-06-07 17:35 • 来自相关话题

在mongodb中参数查看数据库中的表是报错:

Warning: unable to run listCollections, attempting to approximate collection names by parsing connectionStatus

那是因为设置了密码,但是没有进行认证导致的错误。这个错误为啥不直接说明原因呢。汗
 
直接: db.auth('admin','密码')
认证成功返回1, 然后重新执行show tables就可以看到所有的表了。 查看全部
在mongodb中参数查看数据库中的表是报错:

Warning: unable to run listCollections, attempting to approximate collection names by parsing connectionStatus

那是因为设置了密码,但是没有进行认证导致的错误。这个错误为啥不直接说明原因呢。汗
 
直接: db.auth('admin','密码')
认证成功返回1, 然后重新执行show tables就可以看到所有的表了。

python连接mongodb集群 cluster

数据库李魔佛 发表了文章 • 0 个评论 • 887 次浏览 • 2019-06-03 15:55 • 来自相关话题

网上资料比较少,自己测试了下。
连接方法如下:import pymongo
db = pymongo.MongoClient('mongodb://10.18.6.46,10.18.6.26,10.18.6.102')上面默认的端口do都是27017,如果是其他端口,需要这样修改:db = pymongo.MongoClient('mongodb://10.18.6.46:8888,10.18.6.26:9999,10.18.6.102:7777')
然后就可以正常读写数据库:
 
读:coll=db['testdb']['testcollection'].find()
for i in coll:
print(i)输出内容:{'_id': ObjectId('5cf4c7981ee9edff72e5c503'), 'username': 'hello'}
{'_id': ObjectId('5cf4c7991ee9edff72e5c504'), 'username': 'hello'}
{'_id': ObjectId('5cf4c7991ee9edff72e5c505'), 'username': 'hello'}
{'_id': ObjectId('5cf4c79a1ee9edff72e5c506'), 'username': 'hello'}
{'_id': ObjectId('5cf4c7b21ee9edff72e5c507'), 'username': 'hello world'}



 
写:collection = db['testdb']['testcollection']

for i in range(10):
collection.insert({'username':'huston{}'.format(i)})
 
原创文章,转载请注明出处:
http://30daydo.com/article/494
  查看全部
网上资料比较少,自己测试了下。
连接方法如下:
import pymongo
db = pymongo.MongoClient('mongodb://10.18.6.46,10.18.6.26,10.18.6.102')
上面默认的端口do都是27017,如果是其他端口,需要这样修改:
db = pymongo.MongoClient('mongodb://10.18.6.46:8888,10.18.6.26:9999,10.18.6.102:7777')

然后就可以正常读写数据库:
 
读:
coll=db['testdb']['testcollection'].find()
for i in coll:
print(i)
输出内容:
{'_id': ObjectId('5cf4c7981ee9edff72e5c503'), 'username': 'hello'}
{'_id': ObjectId('5cf4c7991ee9edff72e5c504'), 'username': 'hello'}
{'_id': ObjectId('5cf4c7991ee9edff72e5c505'), 'username': 'hello'}
{'_id': ObjectId('5cf4c79a1ee9edff72e5c506'), 'username': 'hello'}
{'_id': ObjectId('5cf4c7b21ee9edff72e5c507'), 'username': 'hello world'}



 
写:
collection = db['testdb']['testcollection']

for i in range(10):
collection.insert({'username':'huston{}'.format(i)})

 
原创文章,转载请注明出处:
http://30daydo.com/article/494