I am new to node.js and socket.io and I am trying to write a small server that will update a webpage based on python output.
Eventually this will be used for a temperature sensor so for now I have a dummy script which prints temperature values every few seconds:
Thermostat.py
import random, time
for x in range(10):
print(str(random.randint(23,28))+" C")
time.sleep(random.uniform(0.4,5))
Here's a cut down version of the server:
Index.js
var sys = require('sys'),
spawn = require('child_process').spawn,
thermostat = spawn('python', ["thermostat.py"]),
app = require('express')(),
http = require('http').Server(app),
io = require('socket.io')(http);
thermostat.stdout.on('data', function (output) {
var temp = String(output);
console.log(temp);
io.sockets.emit('temp-update', { data: temp});
});
app.get('/', function(req, res){
res.sendFile(__dirname + '/index.html');
});
And finally the web page:
Index.html
<!doctype html>
<html>
<head>
<title>Live temperature</title>
<link rel="stylesheet" type="text/css" href="styles.css">
</head>
<body>
<div id="liveTemp">Loading...</div>
<script src="http://code.jquery.com/jquery-1.11.1.js"></script>
<script src="/socket.io/socket.io.js"></script>
<script>
var socket = io();
socket.on('temp-update', function (msg) {
$('#liveTemp').html(msg.data)
});
</script>
</body>
</html>
The problem is nodejs seems to recieve all of the temperature values at once, and instead of getting 10 temperature values at random intervals, I get all of the values in one long string after the script has finished:
You need to disable output buffering in python. This can be done many different ways, including:
Setting the PYTHONUNBUFFERED environment variable
Passing the -u switch to the python executable
Calling sys.stdout.flush() after each write (or print() in your case) to stdout
For Python 3.3+ you can pass flush=true to print(): print('Hello World!', flush=True)
Additionally, in your node code, (even though you have a sleep in your python code and you are now flushing stdout) you really should not assume that output in your 'data' handler for thermostat.stdout is always going to be just one line.
Related
follow by discussion Get output of python script from within python script
I create online webpage (.html) run other .py script result, but face model not found error
logically seems the python code is fine, might the setting error or other issue I don't come up myself
printbob.py
#!/usr/bin/env python
import sys
def main(args):
for arg in args:
print(arg)
if __name__ == '__main__':
main(sys.argv)
test_0109_003.html
<html>
<head>
<link rel="stylesheet" href="https://pyscript.net/latest/pyscript.css" />
<script defer src="https://pyscript.net/latest/pyscript.js"></script>
</head>
<body>
<b><p>title test 1.10-test_get_ print </p></b>
<br>
<py-script>
import printbob
printbob.main('arg1 arg2 arg3 arg4'.split(' '))
</py-script>
</body>
</html>
(pic 01) the result website showing
(pic 02) I put .py and .html script in WinSCP, online host system
so how to solve this problem, I locate that there might be the resaon
my winscp ip port is private that public cannot access to private's file, I'm not sure if this the reason, and if so, how to deal with it?
I have an arduino program and set-up which detects the number of cars from a parking lot. The number of cars is printed on the serial every time when the sensor detects a car in front of the barrier.
I want to print the number of cars from the parking lot into a small web app. I use Tera Term to scan my serial bus and put the output data into a file text ( data.txt) . Then i use python to read the value from that text file and render it into a HTML page on a web app.
Here is the python code :
from flask import Flask, render_template
import logging
import requests
# Initialize the Flask application
app = Flask(__name__)
# Define a route for the default URL, which loads the form
#app.route("/")
def form():
with open('date.txt') as f:
data = []
lines = f.read().splitlines()
data.append(lines)
for i in data:
return render_template('index.html', variable=data)
if __name__ == "__main__":
app.run()
here is index.html
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Arduino Project</title>
<style>
body{
background: antiquewhite;
}
h1 {color:red;
text-align: center;}
h2 {color:blue;
text-align: center;}
</style>
</head>
<body>
<h1> - Arduino - </h1>
<h2> Number of cars in the parking place: {{ variable }}<br></h2>
<script> setTimeout(function(){
window.location.reload(1);
}, 5000);
</script>
</body>
</html>
It works fine, but i want to have only a variable which updates every 5 seconds,when the page is refreshed.I dont want to see all values from the date.txt,just the last one.
This is how my web app looks like with this code until now :
(ignore the error message)
enter image description here
Returning multiples times is not possible.
A return statement is used to end the execution of the function call
and “returns” the result (value of the expression following the return
keyword) to the caller. The statements after the return statements are
not executed.
So this part could be adjusted:
for i in data:
return render_template('index.html', variable=data)
You said you want the last line only. So replace above with this:
return render_template('index.html', variable=data[-1])
Documentation
Getting the last element of a list
https://www.geeksforgeeks.org/python-return-statement/
I have written a game in Python using the PyGame library that I am trying to embed into an HTML page to allow me to play in a web browser.
I am attempting to do this using the JavaScript library Skulpt. I have attached a test script below that successfully outputs the print statement below.
skulpt.html
<html>
<head>
<script src="assets/skulpt/skulpt.js" type="text/javascript"></script>
</head>
<body>
<textarea id="pythonCode">
print "I am python."
</textarea><br />
<pre id="output"></pre>
<script type="text/javascript">
function outf(text) {
var mypre = document.getElementById("output");
mypre.innerHTML = mypre.innerHTML + text;
}
var code = document.getElementById("pythonCode").value;
Sk.configure({output:outf});
eval(Sk.importMainWithBody("<stdin>",false,code));
</script>
</body>
</html>
Output of skulpt.html:
The issue that I am having is that when I use my game code instead of the simple print statement shown above it produces the error seen below;
I have included all relevant images to my web servers' directory at the correct path. I am unsure of why this error is being produced. Any help would be much appreciated, thanks!
Also, here is the attached Python game code (and a live demo of the error):
http://nicolasward.com/portfolio/skulpt.html
You have a lot of indentation on line 1 -> remember, in python, indentation always matters. Take away all those spaces/tabs on the first line and it should run.
I have 1 very simple web application I am building right now but am very new to flask and jinja (and web development as a whole actually).
I have a watch folder, which will be getting an image sent to it via ftp on a pulse for ever. This wtch folder will only ever have one image in. Every 1 minute, the old image is replaced by a new image, with a new timestamp.
I would like to dynamically update the page, (and displayed timestamp) on a pulse as well, without having to reload any banners or static images that I will add later. I only want to update the following two lines out of the "Channels.Jinja" sample to follow.
<br>{{screenshot_datetime}}<br/>
<img src={{screenshot_location}} width="100%"/>
Channels.Jinja
<!DOCTYPE HTML>
<html>
<head>
<title>Training</title>
</head>
<body bgcolor=white>
<div id=main>
<br>Date and Time of Screenshot <br/>
<br>{{screenshot_datetime}}<br/>
<img src={{screenshot_location}} width="100%"/>
</div>
<div id='test'>
<p>
<script>
var myVar=setInterval(function(){get_image()},1000);
function get_image() {
$.ajax({
type: 'GET',
cache: false,
url: 'get_data',
success: function({{data}}) {
$('img').attr('src', data);
}
});
}
</script>
</p>
</div>
</body>
</html>
Channels.py
def render_channel_route(cr):
static_folder = os.path.join('static',cr)
file_list = os.listdir(static_folder)
channel_files = [f for f in file_list if f.startswith(cr)]
if not channel_files :
logger.error('Could not find image file for Channel. File should start with {0}'.format(cr))
abort(404)
img = os.path.join(static_folder,file_list[0])
ts = get_time_from_filename(file_list[0],cr)
return render_template('Channels.jinja',screenshot_datetime=time.strftime('%c',ts),screenshot_location=img)
#app.route('/channel01-10')
def first_tab():
return render_channel_route('channel01-10')
#app.route('/get_data', methods=['GET'])
def get_data():
return render_template('Channels.jinja',
screenshot_datetime=time.strftime('%c',ts),screenshot_location=img)
Im at a loss, Ive been bumbling around for a while now. Any and all advice is welcome! I am seeing a 304 response upon refresh, but not even the timer i am trying to put on it is working. Pardon sloppy code, highly volatile code is getting changed often -_-
I don't know it there is a "special" way to deal with Ajax using some Flask extension, but in the "normal" Ajax flow first you need to use url_for to put the correct url in your Ajax call and return the data formatted in some way (in my example in JSON) and not to render the template again:
$.ajax({
type: 'GET',
cache: false,
url: "{{ url_for('get_data') }}",
success: function(resp){
$('img').attr('src', resp.url);
$('#sst').html(resp.time);
}
});
So, in your get_data function in your controller you have to get the time and the path again for your image an then return some like this (to fit in my example before):
from flask import json
#app.route('/get_data', methods=['GET'])
def get_data():
#get time and path
time=...
path=...
return json.dumps({time:time,url:path}), 200, {'Content-Type':'application/json'}
Look that I use $('#sst') so you have to put in your HTML:
<br><span id='sst'>{{screenshot_datetime}}</span><br/>
I want to have a web page where you click a button, by using AJAX I get a string from a python script, then display that string in a paragraph HTML element.
I know I can do this by using Python, WSGI & AJAX (theoretically I can do it this way) but its waaaay too difficult. I am experienced with CGI & python.
So can I do the above using CGI?
If I can how do the python script work, exactly the same as when serving a page using CGI?
This doesn't work:
import cgitb; cgitb.enable()
import cgi
import os
print "Content-Type: text/html\n"
input_data = cgi.FieldStorage()
print "hello"
When I click my button in my page, nothing happens & my CGI server (which works fine for cgi page requests) gives me a http 501 error.
My html & javascript:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<script type="text/javascript">
<!--
function onTest( dest, params )
{
var xmlhttp;
if (window.XMLHttpRequest)
{// code for IE7+, Firefox, Chrome, Opera, Safari
xmlhttp=new XMLHttpRequest();
}
else
{// code for IE6, IE5
xmlhttp=new ActiveXObject("Microsoft.XMLHTTP");
}
xmlhttp.onreadystatechange=function()
{
if (xmlhttp.readyState==4 && xmlhttp.status==200)
{
document.getElementById( "bb" ).innerHTML = xmlhttp.responseText;
}
}
xmlhttp.open("POST",dest,true);
xmlhttp.setRequestHeader("Content-type","application/x-www-form-urlencoded");
xmlhttp.send( params );
}
-->
</script>
</head>
<body>
<p id="bb"> abcdef </p>
Click it
</body>
</html>
Here are 3 files [my.html, myCGI.py, myPyServer.py]. In windows XP I put them all in the same directory and double-click on myPyServer.py and things work very well.
my.html is the same as your html except:
yours: Click it
mine: Click it
myCGI.py is pretty close to yours
import cgitb; cgitb.enable()
import cgi
import os
input_data = cgi.FieldStorage()
if input_data:
print "Content-Type: text/html\n"
print "hello"
else:
f = open('my.html', 'r'); s = f.read(); f.close()
print "Content-Type: text/html\n"
print s
myPyServer.py
import CGIHTTPServer
import BaseHTTPServer
import sys
class Handler(CGIHTTPServer.CGIHTTPRequestHandler):
cgi_directories = ["/"] #make sure this is where you want it. [was "/cgi"]
PORT = 8000
httpd = BaseHTTPServer.HTTPServer(("", PORT), Handler)
# see effbot http://effbot.org/librarybook/thread.htm
def runserver():
print "serving at port", PORT
httpd.serve_forever()
import thread
thread.start_new_thread(runserver, ())
print "opening browser"
import webbrowser
url = 'http://127.0.0.1:8000/myCGI.py'
webbrowser.open_new(url)
quit = 'n'
while not(quit=='quit'):
quit = raw_input('\n ***Type "quit" and hit return to exit myPyServer.*** \n\n')
print "myPyServer will now exit."
sys.exit(0)
Of course you can use plain old CGI if you want. Your code works fine for me. (The "abcdef" turns into "hello" when the link is clicked.)
You must have some simple error in your setup. I'd check file permissions on your test scripts (a+rx), which might have been overlooked. Also I assume you've got a "#!/usr/bin/env python" (or equivalent) at the top of your cgi script (it is omitted in your example above).
Check out sajax:
http://www.modernmethod.com/sajax/
There's a python library and example in the download. You can have one CGI script that can handle your view and implement any AJAX call.
Here is one simple example using Python CGI and ajax.
http://www.ssiddique.info/writing-your-first-python-cgi-ajax-script.html