深海游弋的鱼 – 第 6 页

用Python在地图上模拟疫情扩散

最近在研究热力图，发现了一篇可能有用的Python模拟疫情扩散的文章，可以部分模拟热力图，整篇文章原文内容如下：

ubuntu 14.04.5下安装多版本Python(2.7.6/3.4.3/3.6.4)

系统环境：ubuntu14.04.5 LTS，系统默认的python版本为2.7.4/3.4.3。

但是实际工作中，某些通过pip安装的开发包需要不低于某个版本的python才能正常工作，比如ansible-2.4.2.0,明确只支持python-3.5以上的版本。在低版本的python上，无法正常运行。

而如果我们贸然更新系统python版本的话，会导致系统异常。因此我们借助pyenv实现基于用户的python版本定制。

安装pyenv：

$ git clone https://github.com/pyenv/pyenv.git ~/.pyenv

$ echo 'export PYENV_ROOT="$HOME/.pyenv"' >> ~/.bashrc

$ echo 'export PATH="$PYENV_ROOT/bin:$PATH"' >> ~/.bashrc

$ echo 'eval "$(pyenv init -)"' >> ~/.bashrc

$ exec $SHELL -l

$ git clone https://github.com/pyenv/pyenv.git ~/.pyenv

$ echo 'export PYENV_ROOT="$HOME/.pyenv"' >> ~/.bashrc

$ echo 'export PATH="$PYENV_ROOT/bin:$PATH"' >> ~/.bashrc

$ echo 'eval "$(pyenv init -)"' >> ~/.bashrc

$ exec $SHELL -l

查看可以安装的python版本：

$ pyenv install --list

1	$ pyenv install --list

这里以安装python-3.6.4为例，首先安装依赖：

$ sudo apt-get install -y make build-essential

1	$ sudo apt-get install -y make build-essential

安装python：

# 要求开启Python动态库的支持（默认是全部静态编译），否则在安装某些插件的时候会出现无法正常链接的情况，比如 mod_wsgi
$ export PYTHON_CONFIGURE_OPTS="--enable-shared"

$ pyenv install 3.6.4 -vvv

# 要求开启Python动态库的支持（默认是全部静态编译），否则在安装某些插件的时候会出现无法正常链接的情况，比如 mod_wsgi

$ export PYTHON_CONFIGURE_OPTS="--enable-shared"

$ pyenv install 3.6.4 -vvv

该命令会从github上下载python的源代码，并解压到/tmp目录下，然后在/tmp中执行编译工作。若依赖包没有安装，则会出现编译错误，需要在安装依赖包之后重新执行该命令。

安装完成之后，需要使用如下命令对数据库进行更新：

$ pyenv rehash

1	$ pyenv rehash

查看当前已经安装的python版本

$ pyenv versions
* system (set by /home/xxx/.pyenv/version)
3.6.4

$ pyenv versions

* system (set by /home/xxx/.pyenv/version)

3.6.4

其中星号代表是当前系统正在使用的python版本是系统自带的。

设置全局的python版本

$ pyenv global 3.6.4

$ pyenv versions
  system
* 3.6.4 (set by /home/xxx/.pyenv/version)

$ pyenv global 3.6.4

$ pyenv versions

system

* 3.6.4 (set by /home/xxx/.pyenv/version)

从上面，我们可以看出来当前的python版本已经变为了3.6.4。也可以使用pyenv local或pyenv shell临时改变python的版本。

如果需要还原设定的python版本为系统自带的版本，则执行如下命令：

$ pyenv global system

1	$ pyenv global system

确认python版本

$ python
Python 3.6.4 (default, Jan  9 2018, 11:21:57) 
[GCC 4.8.4] on linux
Type "help", "copyright", "credits" or "license" for more information.

$ python

Python 3.6.4 (default, Jan 9 2018, 11:21:57)

[GCC 4.8.4] on linux

Type "help", "copyright", "credits" or "license" for more information.

上面的操作会导致在当前用户下，执行python或者python3命令的时候都会被定向到python-3.6.4，如果只想执行python3命令的时候被定向到python-3.6.4，则可以直接删除python这个链接：

# 注意，这个链接删除后，可能导致ros indigo的初始化异常，因此，这部分的改动要慎重

$ rm -rf ~/.pyenv/versions/3.6.4/bin/python

# 注意，这个链接删除后，可能导致ros indigo的初始化异常，因此，这部分的改动要慎重

$ rm -rf ~/.pyenv/versions/3.6.4/bin/python

安装pip：

$ wget https://bootstrap.pypa.io/get-pip.py

$ python3 get-pip.py

$ rm -rf get-pip.py

$ pip3 install --upgrade pip

$ wget https://bootstrap.pypa.io/get-pip.py

$ python3 get-pip.py

$ rm -rf get-pip.py

$ pip3 install --upgrade pip

安装完成之后，需要使用如下命令对数据库进行更新：

$ pyenv rehash

1	$ pyenv rehash

注意事项：

输入python即可使用新版的python
系统自带的脚本会以/usr/bin/python的方式直接调用老版本的python，因而不会对系统脚本产生影响
使用pip安装第三方模块时会安装到~/.pyenv/versions/3.6.4下，不会和系统模块发生冲突
使用pip安装模块后，可能需要执行pyenv rehash更新数据库

参考链接

Python中用Ctrl+C终止threading初始化的多线程脚本

在编写Python脚本的时候，难免会遇到使用多线程操作的情况。

正常情况下，我们都习惯在Shell中使用Ctrl+C终止脚本的执行，但是在多线程环境中，我们发现Ctrl+C并不能有效终止开启了多线程的脚本。

由于Python提供的threading模块并没有提供线程的退出接口，导致我们没有办法终止已经正常运行的线程，尤其是线程被阻塞在内核的情况下。

解决这个问题的办法就是在线程初始化之后设置为守护模式（setDaemon），并且不要调用join阻塞主线程。这样当主线程退出的时候，其他线程也随之退出了。

下面是我们解决这种问题的一个例子：

#!/bin/env python
# -*- coding: utf-8 -*-

import threading
import signal
import sys
import time

global is_exit
is_exit = False

def doWork(i):
    print "thread[%d] enter\n"%(i)
    while not is_exit:
       time.sleep(0.2)
    print "thread[%d] terminated\n"%(i)

def sig_handler(signum, frame):
    is_exit = True
    sys.exit(0)
    
if __name__ == "__main__":
    signal.signal(signal.SIGINT, sig_handler)
    signal.signal(signal.SIGTERM, sig_handler)
    cc = 5
    for i in range(cc):
        t = threading.Thread(target=doWork, args=(i,))
        t.setDaemon(True)
        t.start()

    raw_input("Waiting For Ctrl+C\n")

#!/bin/env python

# -*- coding: utf-8 -*-

import threading

import signal

import sys

import time

global is_exit

is_exit = False

def doWork(i):

print "thread[%d] enter\n"%(i)

while not is_exit:

time.sleep(0.2)

print "thread[%d] terminated\n"%(i)

def sig_handler(signum, frame):

is_exit = True

sys.exit(0)

if __name__ == "__main__":

signal.signal(signal.SIGINT, sig_handler)

signal.signal(signal.SIGTERM, sig_handler)

cc = 5

for i in range(cc):

t = threading.Thread(target=doWork, args=(i,))

t.setDaemon(True)

t.start()

raw_input("Waiting For Ctrl+C\n")

参考链接

Python 中用 Ctrl+C 终止多线程程序的问题解决

Python简单实现WebSocket

实现一个简单的聊天室程序，代码如下：

#-*- coding:utf8 -*-

import threading
import hashlib
import socket
import base64

global clients
clients = {}

#通知客户端
def notify(message):
    for connection in clients.values():
        connection.send('%c%c%s' % (0x81, len(message), message))

#客户端处理线程
class websocket_thread(threading.Thread):
    def __init__(self, connection, username):
        super(websocket_thread, self).__init__()
        self.connection = connection
        self.username = username
    
    def run(self):
        print 'new websocket client joined!'
        data = self.connection.recv(1024)
        headers = self.parse_headers(data)
        token = self.generate_token(headers['Sec-WebSocket-Key'])
        self.connection.send('\
HTTP/1.1 101 WebSocket Protocol Hybi-10\r\n\
Upgrade: WebSocket\r\n\
Connection: Upgrade\r\n\
Sec-WebSocket-Accept: %s\r\n\r\n' % token)
        while True:
            try:
                data = self.connection.recv(1024)
            except socket.error, e:
                print "unexpected error: ", e
                clients.pop(self.username)
                break
            data = self.parse_data(data)
            if len(data) == 0:
                continue
            message = self.username + ": " + data
            notify(message)
            
    def parse_data(self, msg):
        v = ord(msg[1]) & 0x7f
        if v == 0x7e:
            p = 4
        elif v == 0x7f:
            p = 10
        else:
            p = 2
        mask = msg[p:p+4]
        data = msg[p+4:]
        return ''.join([chr(ord(v) ^ ord(mask[k%4])) for k, v in enumerate(data)])
        
    def parse_headers(self, msg):
        headers = {}
        header, data = msg.split('\r\n\r\n', 1)
        for line in header.split('\r\n')[1:]:
            key, value = line.split(': ', 1)
            headers[key] = value
        headers['data'] = data
        return headers

    def generate_token(self, msg):
        key = msg + '258EAFA5-E914-47DA-95CA-C5AB0DC85B11'
        ser_key = hashlib.sha1(key).digest()
        return base64.b64encode(ser_key)

#服务端
class websocket_server(threading.Thread):
    def __init__(self, port):
        super(websocket_server, self).__init__()
        self.port = port

    def run(self):
        sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
        sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
        sock.bind(('127.0.0.1', self.port))
        sock.listen(5)
        print 'websocket server started!'
        while True:
            connection, address = sock.accept()
            try:
                username = "ID" + str(address[1])
                thread = websocket_thread(connection, username)
                thread.start()
                clients[username] = connection
            except socket.timeout:
                print 'websocket connection timeout!'

if __name__ == '__main__':
    server = websocket_server(9000)
    server.start()

#-*- coding:utf8 -*-

import threading

import hashlib

import socket

import base64

global clients

clients = {}

#通知客户端

def notify(message):

for connection in clients.values():

connection.send('%c%c%s' % (0x81, len(message), message))

#客户端处理线程

class websocket_thread(threading.Thread):

def __init__(self, connection, username):

super(websocket_thread, self).__init__()

self.connection = connection

self.username = username

def run(self):

print 'new websocket client joined!'

data = self.connection.recv(1024)

headers = self.parse_headers(data)

token = self.generate_token(headers['Sec-WebSocket-Key'])

self.connection.send('\

HTTP/1.1 101 WebSocket Protocol Hybi-10\r\n\

Upgrade: WebSocket\r\n\

Connection: Upgrade\r\n\

Sec-WebSocket-Accept: %s\r\n\r\n' % token)

while True:

try:

data = self.connection.recv(1024)

except socket.error, e:

print "unexpected error: ", e

clients.pop(self.username)

break

data = self.parse_data(data)

if len(data) == 0:

continue

message = self.username + ": " + data

notify(message)

def parse_data(self, msg):

v = ord(msg[1]) & 0x7f

if v == 0x7e:

p = 4

elif v == 0x7f:

p = 10

else:

p = 2

mask = msg[p:p+4]

data = msg[p+4:]

return ''.join([chr(ord(v) ^ ord(mask[k%4])) for k, v in enumerate(data)])

def parse_headers(self, msg):

headers = {}

header, data = msg.split('\r\n\r\n', 1)

for line in header.split('\r\n')[1:]:

key, value = line.split(': ', 1)

headers[key] = value

headers['data'] = data

return headers

def generate_token(self, msg):

key = msg + '258EAFA5-E914-47DA-95CA-C5AB0DC85B11'

ser_key = hashlib.sha1(key).digest()

return base64.b64encode(ser_key)

#服务端

class websocket_server(threading.Thread):

def __init__(self, port):

super(websocket_server, self).__init__()

self.port = port

def run(self):

sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)

sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)

sock.bind(('127.0.0.1', self.port))

sock.listen(5)

print 'websocket server started!'

while True:

connection, address = sock.accept()

try:

username = "ID" + str(address[1])

thread = websocket_thread(connection, username)

thread.start()

clients[username] = connection

except socket.timeout:

print 'websocket connection timeout!'

if __name__ == '__main__':

server = websocket_server(9000)

server.start()

测试页面：

<!--
@http://www.cnblogs.com/zhuweisky/p/3930780.html
-->
<!DOCTYPE html>
</html>
    <head>
        <meta charset="utf-8">
    </head>
    <body>
        <h3>WebSocketTest</h3>
        <div id="login">
            <div>
                <input id="serverIP" type="text" placeholder="服务器IP" value="127.0.0.1" autofocus="autofocus" />
                <input id="serverPort" type="text" placeholder="服务器端口" value="9000" />
                <input id="btnConnect" type="button" value="连接" onclick="connect()" />
            </div>
            <div>
                <input id="sendText" type="text" placeholder="发送文本" value="I'm WebSocket Client!" />
                <input id="btnSend" type="button" value="发送" onclick="send()" />
            </div>
            <div>
                <div>
                    来自服务端的消息
                </div>
                <textarea id="txtContent" cols="50" rows="10" readonly="readonly"></textarea>
            </div>
        </div>
    </body>
    <script>
        var socket;

        function connect() {
            var host = "ws://" + $("serverIP").value + ":" + $("serverPort").value + "/"
            socket = new WebSocket(host);
            try {

                socket.onopen = function (msg) {
                    $("btnConnect").disabled = true;
                    alert("连接成功！");
                };

                socket.onmessage = function (msg) {
                    if (typeof msg.data == "string") {
                        displayContent(msg.data);
                    }
                    else {
                        alert("非文本消息");
                    }
                };

                socket.onclose = function (msg) { alert("socket closed!") };
            }
            catch (ex) {
                log(ex);
            }
        }

        function send() {
            var msg = $("sendText").value
            socket.send(msg);
        }

        window.onbeforeunload = function () {
            try {
                socket.close();
                socket = null;
            }
            catch (ex) {
            }
        };

        function $(id) { return document.getElementById(id); }

        Date.prototype.Format = function (fmt) { //author: meizz 
            var o = {
                "M+": this.getMonth() + 1, //月份 
                "d+": this.getDate(), //日 
                "h+": this.getHours(), //小时 
                "m+": this.getMinutes(), //分 
                "s+": this.getSeconds(), //秒 
                "q+": Math.floor((this.getMonth() + 3) / 3), //季度 
                "S": this.getMilliseconds() //毫秒 
            };
            if (/(y+)/.test(fmt)) fmt = fmt.replace(RegExp.$1, (this.getFullYear() + "").substr(4 - RegExp.$1.length));
            for (var k in o)
                if (new RegExp("(" + k + ")").test(fmt)) fmt = fmt.replace(RegExp.$1, (RegExp.$1.length == 1) ? (o[k]) : (("00" + o[k]).substr(("" + o[k]).length)));
            return fmt;
        }

        function displayContent(msg) {
            $("txtContent").value += "\r\n" +new Date().Format("yyyy/MM/dd hh:mm:ss")+ ":  " + msg;
        }
        function onkey(event) { if (event.keyCode == 13) { send(); } }
    </script>
</html>

<!--

@http://www.cnblogs.com/zhuweisky/p/3930780.html

-->

<!DOCTYPE html>

</html>

<head>

</head>

<body>

<h3>WebSocketTest</h3>

<div>

</div>

<div>

</div>

<div>

来自服务端的消息

</div>

</div>

</body>

var socket;

function connect() {

var host = "ws://" + $("serverIP").value + ":" + $("serverPort").value + "/"

socket = new WebSocket(host);

try {

socket.onopen = function (msg) {

$("btnConnect").disabled = true;

alert("连接成功！");

};

socket.onmessage = function (msg) {

if (typeof msg.data == "string") {

displayContent(msg.data);

}

else {

alert("非文本消息");

}

};

socket.onclose = function (msg) { alert("socket closed!") };

}

catch (ex) {

log(ex);

}

function send() {

var msg = $("sendText").value

socket.send(msg);

}

window.onbeforeunload = function () {

try {

socket.close();

socket = null;

}

catch (ex) {

}

};

function $(id) { return document.getElementById(id); }

Date.prototype.Format = function (fmt) { //author: meizz

var o = {

"M+": this.getMonth() + 1, //月份

"d+": this.getDate(), //日

"h+": this.getHours(), //小时

"m+": this.getMinutes(), //分

"s+": this.getSeconds(), //秒

"q+": Math.floor((this.getMonth() + 3) / 3), //季度

"S": this.getMilliseconds() //毫秒

};

if (/(y+)/.test(fmt)) fmt = fmt.replace(RegExp.$1, (this.getFullYear() + "").substr(4 - RegExp.$1.length));

for (var k in o)

if (new RegExp("(" + k + ")").test(fmt)) fmt = fmt.replace(RegExp.$1, (RegExp.$1.length == 1) ? (o[k]) : (("00" + o[k]).substr(("" + o[k]).length)));

return fmt;

}

function displayContent(msg) {

$("txtContent").value += "\r\n" +new Date().Format("yyyy/MM/dd hh:mm:ss")+ ": " + msg;

}

function onkey(event) { if (event.keyCode == 13) { send(); } }

</script>

</html>

参考链接

python简单实现websocket

Ubuntu 16.04下用Python显示YUV格式的图片

YUV420p to RGB & view

from PIL import Image
import sys
from struct import *
import array

if len(sys.argv) != 4:
        print "***** Usage syntax Error!!!! *****\n"
        print "Usage:"
        print "python <script> <.yuv file yuv420p> <width&gt> <height> "
        sys.exit(1) # exit
else:
        pass

image_name = sys.argv[1]
width = int(sys.argv[2])
height = int(sys.argv[3])

y = array.array('B')
u = array.array('B')
v = array.array('B')

f_y = open(image_name, "rb")
f_uv = open(image_name, "rb")
f_uv.seek(width*height, 1)

image_out = Image.new("RGB", (width, height))
pix = image_out.load()

print "width=", width, "height=", height

for i in range(0, height/2):
    for j in range(0, width/2):
        u.append(ord(f_uv.read(1)));

for i in range(0, height/2):
    for j in range(0, width/2):
        v.append(ord(f_uv.read(1)));
for i in range(0,height):
    for j in range(0, width):
        y.append(ord(f_y.read(1)));
        #print "i=", i, "j=", j , (i*width), ((i*width) +j)
        #pix[j, i] = y[(i*width) +j], y[(i*width) +j], y[(i*width) +j]
        Y_val = y[(i*width)+j]
        U_val = u[((i/2)*(width/2))+(j/2)]
        V_val = v[((i/2)*(width/2))+(j/2)]
        B = 1.164 * (Y_val-16) + 2.018 * (U_val - 128)
        G = 1.164 * (Y_val-16) - 0.813 * (V_val - 128) - 0.391 * (U_val - 128)
        R = 1.164 * (Y_val-16) + 1.596*(V_val - 128)
        pix[j, i] = int(R), int(G), int(B)

######################################################
# B = 1.164(Y - 16)                   + 2.018(U - 128)
# G = 1.164(Y - 16) - 0.813(V - 128) - 0.391(U - 128)
# R = 1.164(Y - 16) + 1.596(V - 128)
######################################################

#image_out.save("out.bmp")
image_out.show()

from PIL import Image

import sys

from struct import *

import array

if len(sys.argv) != 4:

print "***** Usage syntax Error!!!! *****\n"

print "Usage:"

print "python <script> <.yuv file yuv420p> <width&gt> <height> "

sys.exit(1) # exit

else:

pass

image_name = sys.argv[1]

width = int(sys.argv[2])

height = int(sys.argv[3])

y = array.array('B')

u = array.array('B')

v = array.array('B')

f_y = open(image_name, "rb")

f_uv = open(image_name, "rb")

f_uv.seek(width*height, 1)

image_out = Image.new("RGB", (width, height))

pix = image_out.load()

print "width=", width, "height=", height

for i in range(0, height/2):

for j in range(0, width/2):

u.append(ord(f_uv.read(1)));

for i in range(0, height/2):

for j in range(0, width/2):

v.append(ord(f_uv.read(1)));

for i in range(0,height):

for j in range(0, width):

y.append(ord(f_y.read(1)));

#print "i=", i, "j=", j , (i*width), ((i*width) +j)

#pix[j, i] = y[(i*width) +j], y[(i*width) +j], y[(i*width) +j]

Y_val = y[(i*width)+j]

U_val = u[((i/2)*(width/2))+(j/2)]

V_val = v[((i/2)*(width/2))+(j/2)]

B = 1.164 * (Y_val-16) + 2.018 * (U_val - 128)

G = 1.164 * (Y_val-16) - 0.813 * (V_val - 128) - 0.391 * (U_val - 128)

R = 1.164 * (Y_val-16) + 1.596*(V_val - 128)

pix[j, i] = int(R), int(G), int(B)

######################################################

# B = 1.164(Y - 16) + 2.018(U - 128)

# G = 1.164(Y - 16) - 0.813(V - 128) - 0.391(U - 128)

# R = 1.164(Y - 16) + 1.596(V - 128)

######################################################

#image_out.save("out.bmp")

image_out.show()

UYVY/YUV422 to RGB and view:

from PIL import Image
import sys
from struct import *
import array
 
if len(sys.argv) != 4:
        print "***** Usage syntax Error!!!! *****\n"
        print "Usage:"
        print "python <script> <.yuv file uyvy422> <width&gt> <height> "
        sys.exit(1) # exit
else:
        pass
 
image_name = sys.argv[1]
width = int(sys.argv[2])
height = int(sys.argv[3])
 
y = array.array('B')
u = array.array('B')
v = array.array('B')
 
f_uyvy = open(image_name, "rb")
f_uv = open(image_name, "rb")
f_uv.seek(width*height, 1)
 
image_out = Image.new("RGB", (width, height))
pix = image_out.load()
 
print "width=", width, "height=", height
 
for i in range(0,height):
    for j in range(0, width/2):
        u  = ord(f_uyvy.read(1));
        y1 = ord(f_uyvy.read(1));
        v  = ord(f_uyvy.read(1));
        y2 = ord(f_uyvy.read(1));
 
        B = 1.164 * (y1-16) + 2.018 * (u - 128)
        G = 1.164 * (y1-16) - 0.813 * (v - 128) - 0.391 * (u - 128)
        R = 1.164 * (y1-16) + 1.596*(v - 128)
        pix[j*2, i] = int(R), int(G), int(B)
 
        B = 1.164 * (y2-16) + 2.018 * (u - 128)
        G = 1.164 * (y2-16) - 0.813 * (v - 128) - 0.391 * (u - 128)
        R = 1.164 * (y2-16) + 1.596*(v - 128)
        pix[j*2+1, i] = int(R), int(G), int(B)
 
######################################################
# B = 1.164(Y - 16)                   + 2.018(U - 128)
# G = 1.164(Y - 16) - 0.813(V - 128) - 0.391(U - 128)
# R = 1.164(Y - 16) + 1.596(V - 128)
######################################################
 
#image_out.save("out.bmp")
image_out.show()

from PIL import Image

import sys

from struct import *

import array

if len(sys.argv) != 4:

print "***** Usage syntax Error!!!! *****\n"

print "Usage:"

print "python <script> <.yuv file uyvy422> <width&gt> <height> "

sys.exit(1) # exit

else:

pass

image_name = sys.argv[1]

width = int(sys.argv[2])

height = int(sys.argv[3])

y = array.array('B')

u = array.array('B')

v = array.array('B')

f_uyvy = open(image_name, "rb")

f_uv = open(image_name, "rb")

f_uv.seek(width*height, 1)

image_out = Image.new("RGB", (width, height))

pix = image_out.load()

print "width=", width, "height=", height

for i in range(0,height):

for j in range(0, width/2):

u = ord(f_uyvy.read(1));

y1 = ord(f_uyvy.read(1));

v = ord(f_uyvy.read(1));

y2 = ord(f_uyvy.read(1));

B = 1.164 * (y1-16) + 2.018 * (u - 128)

G = 1.164 * (y1-16) - 0.813 * (v - 128) - 0.391 * (u - 128)

R = 1.164 * (y1-16) + 1.596*(v - 128)

pix[j*2, i] = int(R), int(G), int(B)

B = 1.164 * (y2-16) + 2.018 * (u - 128)

G = 1.164 * (y2-16) - 0.813 * (v - 128) - 0.391 * (u - 128)

R = 1.164 * (y2-16) + 1.596*(v - 128)

pix[j*2+1, i] = int(R), int(G), int(B)

######################################################

# B = 1.164(Y - 16) + 2.018(U - 128)

# G = 1.164(Y - 16) - 0.813(V - 128) - 0.391(U - 128)

# R = 1.164(Y - 16) + 1.596(V - 128)

######################################################

#image_out.save("out.bmp")

image_out.show()

原始链接

YUV to RGB : Python Imaging Library

Python matplotlib.pyplot.draw()在不同版本中的差别导致界面绘制异常问题

在Ubuntu系统上进行如下配置：

$ sudo apt-get update

$ sudo apt-get upgrade

$ sudo apt-get install python-dev

$ sudo apt-get install python-pip

$ sudo pip install --upgrade pip

$ sudo pip install --upgrade urllib3

$ sudo pip install numpy

$ sudo pip install matplotlib

$ sudo apt-get update

$ sudo apt-get upgrade

$ sudo apt-get install python-dev

$ sudo apt-get install python-pip

$ sudo pip install --upgrade pip

$ sudo pip install --upgrade urllib3

$ sudo pip install numpy

$ sudo pip install matplotlib

之后执行如下测试代码：

import sys
import numpy as np
import matplotlib.pyplot as plt

plt.ion()
(fig, axis) = plt.subplots()
bar_plot = axis.barh(0, 8,linewidth = 0)
bar_plot.color= '#ffff00'
for i in range(20):
    axis.set_xlim(xmax = max(i + 1, 10))
    plt.draw()

if sys.version_info < (3, 0):
    raw_input("Press Enter to continue...")
else:
    input("Press Enter to continue...")

import sys

import numpy as np

import matplotlib.pyplot as plt

plt.ion()

(fig, axis) = plt.subplots()

bar_plot = axis.barh(0, 8,linewidth = 0)

bar_plot.color= '#ffff00'

for i in range(20):

axis.set_xlim(xmax = max(i + 1, 10))

plt.draw()

if sys.version_info < (3, 0):

raw_input("Press Enter to continue...")

else:

input("Press Enter to continue...")

上面的测试代码在Ubuntu 14.04.5版本上是可以正常执行的，对应的matplotlib的版本是matplotlib 1.3.1，但是放到Ubuntu 16.04.2系统上则是无法正常显示的,对应的matplotlib的版本是matplotlib 1.5.1。

造成这个问题的原因在于matplotlib.pyplot.draw()，这个函数行为的改变，早期这个函数是同步更新界面的，后来的版本却变成了空闲异步更新界面，只有当matplotlib.pyplot.pause(interval)被调用的时候才会刷新界面。

所以只需要上面的代码修改成如下即可在不同版本之间兼容：

import sys
import numpy as np
import matplotlib.pyplot as plt

plt.ion()
(fig, axis) = plt.subplots()
bar_plot = axis.barh(0, 8,linewidth = 0)
bar_plot.color= '#ffff00'
for i in range(20):
    axis.set_xlim(xmax = max(i + 1, 10))
    plt.draw()
    plt.pause(0.00001)

if sys.version_info < (3, 0):
    raw_input("Press Enter to continue...")
else:
    input("Press Enter to continue...")

import sys

import numpy as np

import matplotlib.pyplot as plt

plt.ion()

(fig, axis) = plt.subplots()

bar_plot = axis.barh(0, 8,linewidth = 0)

bar_plot.color= '#ffff00'

for i in range(20):

axis.set_xlim(xmax = max(i + 1, 10))

plt.draw()

plt.pause(0.00001)

if sys.version_info < (3, 0):

raw_input("Press Enter to continue...")

else:

input("Press Enter to continue...")

注意，我们在matplotlib.pyplot.draw()调用后面增加了matplotlib.pyplot.pause(interval)的调用。

貌似调用fig.canvas.flush_events()更合适？

查看matplotlib的版本使用如下代码：

import matplotlib as mpl
print mpl.__version__

1 2	import matplotlib as mpl print mpl.__version__

参考链接

Ubuntu 14.04系统上Python使用"subprocess.Popen"执行"source"命令报告错误“/bin/sh: source: not found”

使用如下的例子中的代码

import subprocess
def execShellCommand(cmd):
    print cmd
    p = subprocess.Popen(cmd, shell=True, stdout=subprocess.PIPE, stderr=subprocess.STDOUT)
    while True:  
        buff = p.stdout.readline()  
        if buff == '' and p.poll() != None:  
            break
        print buff
    p.wait()


def main():
    execShellCommand("source ~/.profile")

if __name__ == "__main__":
    main()

import subprocess

def execShellCommand(cmd):

print cmd

p = subprocess.Popen(cmd, shell=True, stdout=subprocess.PIPE, stderr=subprocess.STDOUT)

while True:

buff = p.stdout.readline()

if buff == '' and p.poll() != None:

break

print buff

p.wait()

def main():

execShellCommand("source ~/.profile")

if __name__ == "__main__":

main()

运行的时候报告错误

source ~/.profile
/bin/sh: 1: source: not found

1 2	source ~/.profile /bin/sh: 1: source: not found

这个错误发生的原因是subprocess.Popen执行Shell命令的时候默认调用/bin/sh，而source命令/bin/bash才支持的，因此导致错误发生，修改后的脚本如下：

import subprocess
def execShellCommand(cmd):
    print cmd
    p = subprocess.Popen(cmd, shell=True, stdout=subprocess.PIPE, stderr=subprocess.STDOUT,executable="/bin/bash")
    while True:  
        buff = p.stdout.readline()  
        if buff == '' and p.poll() != None:  
            break
        print buff
    p.wait()


def main():
    execShellCommand("source ~/.profile")

if __name__ == "__main__":
    main()

import subprocess

def execShellCommand(cmd):

print cmd

p = subprocess.Popen(cmd, shell=True, stdout=subprocess.PIPE, stderr=subprocess.STDOUT,executable="/bin/bash")

while True:

buff = p.stdout.readline()

if buff == '' and p.poll() != None:

break

print buff

p.wait()

def main():

execShellCommand("source ~/.profile")

if __name__ == "__main__":

main()

注意添加的executable="/bin/bash"，指明了执行脚本的执行程序是/bin/bash。

参考链接

Calling the “source” command from subprocess.Popen

ubuntu 16.04执行letsencrypt的时候报告错误“ImportError: No module named datetime”

网站一直使用letsencrypt提供的HTTPS证书,这个证书的问题在于每隔三个月就必须更新一次，本次更新证书的时候，提示如下错误：

Error: couldn't get currently installed version for /root/.local/share/letsencrypt/bin/letsencrypt:
Traceback (most recent call last):
  File "/root/.local/share/letsencrypt/bin/letsencrypt", line 7, in <module>
    from certbot.main import main
  File "/root/.local/share/letsencrypt/local/lib/python2.7/site-packages/certbot/main.py", line 9, in 

<module>
    from acme import jose
  File "/root/.local/share/letsencrypt/local/lib/python2.7/site-packages/acme/jose/__init__.py", line 

37, in <module>
    from acme.jose.interfaces import JSONDeSerializable
  File "/root/.local/share/letsencrypt/local/lib/python2.7/site-packages/acme/jose/interfaces.py", line 

9, in <module>
    from acme.jose import util
  File "/root/.local/share/letsencrypt/local/lib/python2.7/site-packages/acme/jose/util.py", line 4, in 

<module>
    from cryptography.hazmat.primitives.asymmetric import rsa
  File "/root/.local/share/letsencrypt/local/lib/python2.7/site-

packages/cryptography/hazmat/primitives/asymmetric/rsa.py", line 14, in <module>
    from cryptography.hazmat.backends.interfaces import RSABackend
  File "/root/.local/share/letsencrypt/local/lib/python2.7/site-

packages/cryptography/hazmat/backends/__init__.py", line 7, in <module>
    import pkg_resources
  File "/root/.local/share/letsencrypt/local/lib/python2.7/site-packages/pkg_resources/__init__.py", 

line 36, in <module>
    import plistlib
  File "/usr/lib/python2.7/plistlib.py", line 62, in <module>
    import datetime
ImportError: No module named datetime

Error: couldn't get currently installed version for /root/.local/share/letsencrypt/bin/letsencrypt:

Traceback (most recent call last):

File "/root/.local/share/letsencrypt/bin/letsencrypt", line 7, in <module>

from certbot.main import main

File "/root/.local/share/letsencrypt/local/lib/python2.7/site-packages/certbot/main.py", line 9, in

from acme import jose

File "/root/.local/share/letsencrypt/local/lib/python2.7/site-packages/acme/jose/__init__.py", line

37, in <module>

from acme.jose.interfaces import JSONDeSerializable

File "/root/.local/share/letsencrypt/local/lib/python2.7/site-packages/acme/jose/interfaces.py", line

9, in <module>

from acme.jose import util

File "/root/.local/share/letsencrypt/local/lib/python2.7/site-packages/acme/jose/util.py", line 4, in

from cryptography.hazmat.primitives.asymmetric import rsa

File "/root/.local/share/letsencrypt/local/lib/python2.7/site-

packages/cryptography/hazmat/primitives/asymmetric/rsa.py", line 14, in <module>

from cryptography.hazmat.backends.interfaces import RSABackend

File "/root/.local/share/letsencrypt/local/lib/python2.7/site-

packages/cryptography/hazmat/backends/__init__.py", line 7, in <module>

import pkg_resources

File "/root/.local/share/letsencrypt/local/lib/python2.7/site-packages/pkg_resources/__init__.py",

line 36, in <module>

import plistlib

File "/usr/lib/python2.7/plistlib.py", line 62, in <module>

import datetime

ImportError: No module named datetime

错误发生的原因在于letsencrypt自己构建了一个Python的虚拟环境来隔离，但是早期建立的虚拟环境中是缺少部分软件包的，而自身的BUG导致也没有重新更新虚拟环境，导致出现异常。

解决方法就是删除letsencrypt自己构建的Python的虚拟环境，然后继续执行脚本让他重建即可。

$ rm -rf ~/.local/share/letsencrypt

1	$ rm -rf ~/.local/share/letsencrypt

参考链接

Python 2.7中PIL.Image转换为OpenCV支持的Image格式

pil_image = PIL.Image.open('image.jpg')
cv_image = cv2.cvtColor(numpy.asarray(pil_image), cv2.COLOR_RGB2BGR)

1 2	pil_image = PIL.Image.open('image.jpg') cv_image = cv2.cvtColor(numpy.asarray(pil_image), cv2.COLOR_RGB2BGR)

参考链接

Convert image from PIL to openCV format

TypeError: slice indices must be integers or None or have an index method

执行如下Python脚本时

import numpy as np

dy = [0,1,2]
edy = [0,1,2]

dy[0:2] = np.fix(dy[0:2])
edy[0:2] = np.fix(edy[0:2])

box = [[1,2,3,4],[3,4,5,6]]

box2 = box[dy[0]:edy[2]]

import numpy as np

dy = [0,1,2]

edy = [0,1,2]

dy[0:2] = np.fix(dy[0:2])

edy[0:2] = np.fix(edy[0:2])

box = [[1,2,3,4],[3,4,5,6]]

box2 = box[dy[0]:edy[2]]

会遇到错误信息

Traceback (most recent call last):
  File "test.py", line 11, in <module>
    box2 = box[dy[0]:edy[2]]
TypeError: slice indices must be integers or None or have an __index__ method

Traceback (most recent call last):

File "test.py", line 11, in <module>

box2 = box[dy[0]:edy[2]]

TypeError: slice indices must be integers or None or have an __index__ method

这个提示非常具有迷惑性，会让人不知所措。

其实非常简单

dy[0:2] = np.fix(dy[0:2])

1	dy[0:2] = np.fix(dy[0:2])

这行导致整个数组变成了浮点数格式的数组，可以试着打印出结果，就会发现整个里面的数字完全变成了浮点数。

而浮点数是不可以用来作为数组的下标的。

修改成如下方式即可

import numpy as np

dy = [0,1,2]
edy = [0,1,2]

dy[0:2] = np.fix(dy[0:2])
edy[0:2] = np.fix(edy[0:2])

box = [[1,2,3,4],[3,4,5,6]]

box2 = box[int(dy[0]):int(edy[2])]

import numpy as np

dy = [0,1,2]

edy = [0,1,2]

dy[0:2] = np.fix(dy[0:2])

edy[0:2] = np.fix(edy[0:2])

box = [[1,2,3,4],[3,4,5,6]]

box2 = box[int(dy[0]):int(edy[2])]

请注意最后的

int()

int()

函数，强制转换浮点数为整数。

参考链接

错误异常slice indices must be integers or None or have

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