I am in the process of making my first ever flask/python web app. The app initially displays a form which the user is invited to fill in, then they click on a "submit" button, then the server runs the simulation and creates a PNG file with a graph showing the results, then finally the page is redrawn with the graph displayed. My python code is roughly of this form:
# flask_app.py
#app.route("/", methods=["POST", "GET"])
def home():
if request.method == 'POST':
# bunch of request.form things to scoop the contents of the form
if form_answers_all_good:
for i in range(huge_number):
# some maths
# create png file with results
return render_template("index.htm", foo=bar)
The program is working just fine, but the huge_number loop can take several tens of seconds. So what I would like is some sort of progress indicator - it doesn't have to be a slick animation - even a string readout of the percentage progress would be fine.
Presumably I can change my for loop to something like...
for i in range(huge_number):
# some maths
percentage_done = str(i * 100/huge_number)
and then somehow arrange on the client side to read (poll?) percentage_done so that I put something like:
Completed {% percentage_done %}% so far.
in my index.htm. BTW, my knowledge of things like Javascript, AJAX or come to think of it, almost anything on the client side (apart from HTML) is beginner level.
I have seen a lot of explanations of similar sounding problems but generally they are doing far more complex things than I actually need and I fail to understand them because of my lack of client side knowledge. So for example some solutions might include a snippet of code and I won't actually know where to put it, or I won't know that something else needs to be loaded first in order for the snippet to work.
EDIT: I am hosting my web app on pythonanywhere.com. The list of included modules is here.
EDIT: pythonanywhere.com does not allow streaming :-(
You mention you're new to flask, so I am assuming you're new to flask but comfortable with python and also you are very constrained on what you can use because you're using pythonanywhere. One of the main things is it is single threaded so it makes really hard to scale anything. Also it would be better sticking with pure python as managing the dependencies in python anywhere would be an extra problem to care about, and in the end it's doable to do it using only python builtins.
I focused to show a working solution that you simple copy and paste in pythonanywhere or in your local, rather then showing snippets of code. I will try to:
show the working solution
describe how to replicate it
breakdown the main components and briefly explain
(1) The Working solution
you can access it here(I made a lot of restrictions to try to avoid people from breaking it). The solution just involves two files, flask_app.py and index.html
(1.1) solution code
"./home/{username}/{flask_foldername}/flask_app.py"
from queue import Queue
import time
import random
import threading
from PIL import Image
import flask
from flask import request
import json
import io
import uuid
import base64
### You create a Queue and start a scheduler, Start flask after that
def run_scheduler(app):
sleep_time = 5
while True:
time.sleep(sleep_time)
print("\n"*5)
print(f'images Completed:{app.images_completed}')
print('-----'*20)
if(app.images_toBe_processed.qsize() > 0):
next_image_name = app.images_toBe_processed.get()
print(f"No Images being processed so scheduler will start processing the next image {next_image_name} from the queue")
app.function_to_process_image(next_image_name, app)
else:
pass
def function_to_process_image(image_name, app):
huge_number = 5
R = random.randint(0,256)
G = random.randint(0,256)
B = random.randint(0,256)
for i in range(huge_number):
# some maths
percentage_done = str((i+1)*100/huge_number)
app.images_processing_status[image_name] = percentage_done
time.sleep(1)
app.images_processing_status[image_name] = str(100.0)
img = Image.new('RGB', (60, 30), color =(R,G,B))
b=io.BytesIO()
img.save(b, "jpeg")
app.images_completed[image_name] = {"status":1,"file": b}
print(f"IC from function: {app.images_completed} **************************")
if app.images_processing_status.get("!!total!!",False): app.images_processing_status["!!total!!"]+= 1
else: app.images_processing_status["!!total!!"] = 1
del app.images_processing_status[image_name]
return 0 #process sucessful
class Webserver(flask.Flask):
def __init__(self,*args,**kwargs):
scheduler_func = kwargs["scheduler_func"]
function_to_process_image = kwargs["function_to_process_image"]
queue_MAXSIZE = kwargs["queue_MAXSIZE"]
del kwargs["function_to_process_image"], kwargs["scheduler_func"], kwargs["queue_MAXSIZE"]
super(Webserver, self).__init__(*args, **kwargs)
self.start_time = time.strftime("%d/%m/%Y %H:%M")
self.queue_MAXSIZE = queue_MAXSIZE
self.active_processing_threads = []
self.images_processing_status = {}
self.images_completed = {}
self.images_toBe_processed = Queue(maxsize=queue_MAXSIZE)
self.function_to_process_image = function_to_process_image
self.scheduler_thread = threading.Thread(target=scheduler_func, args=(self,))
app = Webserver(__name__,
template_folder="./templates",
static_folder="./",
static_url_path='',
scheduler_func = run_scheduler,
function_to_process_image = function_to_process_image,
queue_MAXSIZE = 20,
)
### You define a bunch of views
#app.route("/",methods=["GET"])
def send_index_view():
if not flask.current_app.scheduler_thread.isAlive():
flask.current_app.scheduler_thread.start()
return flask.render_template('index.html',queue_size = flask.current_app.images_toBe_processed.qsize(),
max_queue_size =flask.current_app.queue_MAXSIZE , being_processed=len(flask.current_app.active_processing_threads),
total=flask.current_app.images_processing_status.get("!!total!!",0), start_time=flask.current_app.start_time )
#app.route("/process_image",methods=["POST"])
def receive_imageProcessing_request_view():
image_name = json.loads(request.data)["image_name"]
if(flask.current_app.images_toBe_processed.qsize() >= flask.current_app.queue_MAXSIZE ):
while(not flask.current_app.images_toBe_processed.empty()):
flask.current_app.images_toBe_processed.get()
requestedImage_status = {"name":image_name, "id":uuid.uuid1()}
flask.current_app.images_toBe_processed.put(image_name)
return flask.jsonify(requestedImage_status)
#app.route("/check_image_progress",methods=["POST"])
def check_image_progress():
print(f'Current Image being processed: {flask.current_app.images_processing_status}')
print(f'Current Images completed: {flask.current_app.images_completed}')
image_name = json.loads(request.data)["image_name"]
is_finished = flask.current_app.images_completed \
.get(image_name,{"status":0,"file": ''})["status"]
requestedImage_status = {
"is_finished": is_finished,
"progress": flask.current_app.images_processing_status.get(image_name,"0")
}
return flask.jsonify(requestedImage_status) #images_processing_status[image_name]})
#app.route("/get_image",methods=["POST"])
def get_processed_image():
image_name = json.loads(request.data)["image_name"]
file_bytes = flask.current_app.images_completed[image_name]["file"] #open("binary_image.jpeg", 'rb').read()
file_bytes = base64.b64encode(file_bytes.getvalue()).decode()
flask.current_app.images_completed.clear()
return flask.jsonify({image_name:file_bytes}) #images_processing_status[image_name]})
"./home/{username}/{flask_foldername}/templates/index.html"
<html>
<head>
</head>
<body>
<h5> welcome to the index page, give some inputs and get a random RGB image back after some time</h5>
<h5> Wait 10 seconds to be able to send an image request to the server </h5>
<h5>When the page was loaded there were {{queue_size}} images on the queue to be processed, and {{being_processed}} images being processed</h5>
<h5> The max size of the queue is {{max_queue_size}}, and it will be reseted when reaches it</h5>
<h5>A total of {{total}} images were processed since the server was started at {{start_time}}</h5>
<form>
<label for="name">Image name:</label><br>
<input type="text" id="name" name="name" value="ImageName" required><br>
</form>
<button onclick="send();" disabled>Send request to process image </button>
<progress id="progressBar" value="0" max="100"></progress>
<img style="display:block" />
<script>
window.image_name = "";
window.requests = "";
function send(){
var formEl = document.getElementsByTagName("form")[0];
var input = formEl.getElementsByTagName("input")[0];
var RegEx = /^[a-zA-Z0-9]+$/;
var Valid = RegEx.test(input.value);
if(Valid){
window.image_name = input.value;
var xhttp = new XMLHttpRequest();
xhttp.onload = function() {
result=JSON.parse(xhttp.response)
window.requests = setTimeout(check_image_progress, 3000);
};
xhttp.open("POST", "/process_image", true);
xhttp.send(JSON.stringify({"image_name":input.value}));
var buttonEl = document.getElementsByTagName("button")[0];
buttonEl.disabled = true;
buttonEl.innerHTML = "Image sent to process;only one image per session allowed";
}
else{
alert("input not valid, only alphanumeric characters");
}
}
function check_image_progress(){
var xhttp = new XMLHttpRequest();
xhttp.onload = function() {
result=JSON.parse(xhttp.response)
var progressBarEl = document.getElementsByTagName("progress")[0];
if(progressBarEl.value < result["progress"]){
progressBarEl.value=result["progress"];
} else {}
if(result["is_finished"] == true){
clearTimeout(window.requests);
window.requests = setTimeout(get_image,5);
}
else {
window.requests = setTimeout(check_image_progress, 3000);
}
};
xhttp.open("POST", "/check_image_progress", true);
xhttp.send(JSON.stringify({"image_name":window.image_name}));
}
function get_image(){
var xhttp = new XMLHttpRequest();
xhttp.onload = function() {
result=JSON.parse(xhttp.response)
img_base64 = result[window.image_name];
var progressBarEl = document.getElementsByTagName("progress")[0];
progressBarEl.value=100;
clearTimeout(window.requests);
var imgEl = document.getElementsByTagName("img")[0];
console.log(result)
imgEl.src = 'data:image/jpeg;base64,'+img_base64;
};
xhttp.open("POST", "/get_image", true);
xhttp.send(JSON.stringify({"image_name":window.image_name}));
}
setTimeout(function(){document.getElementsByTagName("button")[0].disabled=false;},100);
function hexToBase64(str) {
return btoa(String.fromCharCode.apply(null, str.replace(/\r|\n/g, "").replace(/([\da-fA-F]{2}) ?/g, "0x$1 ").replace(/ +$/, "").split(" ")));
}
</script>
</body>
</html>
(2) How to replicate, and create your own webapp
go to your web app tab in web
scroll down to find the source directory link
click on the flask_app.py and include the flask_app.py code
click on the templates directory, or create if doesn't exists
click on the index.html file and include the index.html code
go back to the web app tab and reload your app
(3) Main components of the app
Some details about pythonanywhere:
Pythoanywhere run a wsgi to start your flask app, it will basically import your app from the flask_app.py and run it.
by default wsgi is run in your /home/{username} folder and not in the /home/{username}/{flask_folder}, you can change this if you want.
Pythonanywhere is single-threaded so you can't rely on sending jobs to background.
The main components to watch out for in the backend:
1) Threads, Flask will be in the main Thread run by wsgi and we will run a child thread scheduler that will keep track of the Queue and schedule the next image to be processed.
2) Flask class: app, the component which handles user requests and send processing requests to the Queue
3) Queue, a Queue that stores in order the request from users to process images
4) Scheduler, The component that decides if a new function process_image call can be run and if yes. It needs to be run in an independent Thread than flask.
5) Encapsulate all those in a custom class Webserver to be able to easily access then (pythonanywhere uses wsgi which makes keeping track of variables created locally hard)
So taking look in the big picture of the code
#lot of imports
+-- 14 lines: from queue import Queue-----------------------------------------------------------------------------------------
# this function will check periodically if there's no images being processed at the moment.
# if no images are being processed check in the queue if there's more images to be processd
# and start the first one in the queue
def run_scheduler(app):
+-- 12 lines: sleep_time = 5 -------------------------------------------------------------------------------------------------
# this function do the math and creates an random RGB image in the end.
def function_to_process_image(image_name, app):
+-- 21 lines: {---------------------------------------------------------------------------------------------------------------
# This class encapsulates all the data structures("state") from our application
# in order to easily access the progress and images information
class Webserver(flask.Flask):
def __init__(self,*args,**kwargs):
+-- 13 lines: scheduler_func = kwargs["scheduler_func"]-----------------------------------------------------------------------
# Here we're instatiating the class
app = Webserver(__name__,
+-- 5 lines: template_folder="./templates",----------------------------------------------------------------------------------
queue_MAXSIZE = 20,
)
### You define a bunch of views
+-- 39 lines: #app.route("/",methods=["GET"]) --------------------------------------------------------------------------------
the main components of the frontend:
send function which is triggered when user clicks the send request to process image button
check_progress function which is triggered by send function to recurrently request the check_progress view in flask to get info about progress. When processing is over we remove the recurrence.
get_image function which is triggered by check_progress when processing is over ('is_finished' = 1)
big picture of the frontend:
<html>
<head>
</head>
<body>
<!-- JUST THE INITIAL HTML elements -->
+-- 12 lines: <h5> welcome to the index page, give some inputs and get a random RGB image back after some time</h5>-----------
<script>
window.image_name = "";
window.requests = "";
function send(){
// SEND image process request when click button and set a timer to call periodically check_image_process
+-- 20 lines: var formEl = document.getElementsByTagName("form")[0];----------------------------------------------------------
}
function check_image_progress(){
// SEND a request to get processing status for a certain image_name
+-- 18 lines: var xhttp = new XMLHttpRequest();-------------------------------------------------------------------------------
}
function get_image(){
// SEND a request to get the image when image_status 'is_processed' = 1
+--- 13 lines: var xhttp = new XMLHttpRequest();------------------------------------------------------------------------------
}
setTimeout(function(){document.getElementsByTagName("button")[0].disabled=false;},100);
</script>
</body>
</html>
You can create a simple stream using Flask stream_with_context and then use yield to send some data about the progress to the client using JSON format. You'll read that data using XMLHttpRequest: progress event and display the progress to the client or update an element with the image when the script is done.
Python Flask code:
Please read inline comments
import time
from flask import Flask, stream_with_context, request, Response
app = Flask(__name__, static_url_path='',static_folder='static')
#app.route('/')
def hello_world():
return app.send_static_file('index.html')
#app.route('/compute-image')
def compute_image():
def generate():
huge_number = 100000
progress = 0
# Start by sending total JSON value to the client stream
yield "{\"total\": %d}" % huge_number
for i in range(huge_number):
# If there is a 100 step progress, send progress JSON value to the client stream
if progress >= 100:
progress = 0
yield "{\"progress\": %d}" % (i)
# Else increment progress by 1 and sleep a bit for demonstration
else:
progress = progress + 1
time.sleep(0.0005)
# Send the generated image location to the client when we're done
yield "{\"img_url\": \"/some/generated/image.png\"}"
# Return the stream context with out generator function
return Response(stream_with_context(generate()))
Client Javascript code:
Please read inline comments
// Compute button
const btnEl = document.getElementById('compute');
// Progress label
const progEl = document.getElementById('progress');
// Time elapsed label
const timeEl = document.getElementById('time');
btnEl.addEventListener('click', function(e) {
btnEl.disabled = true;
progEl.textContent = '';
timeEl.textContent = '';
// Track the AJAX response buffer length
let prevBufferEnd = 0;
// Save the total (huge_number)
let total = 0;
// Save the time we've started
const timeStart = new Date;
const xhr = new XMLHttpRequest();
xhr.addEventListener('progress', function(e) {
// Get the current progress JSON data
let currentProgress = e.currentTarget.responseText.substring(prevBufferEnd, e.currentTarget.responseText.length);
prevBufferEnd = e.currentTarget.responseText.length;
// Parse JSON data
const respData = JSON.parse(currentProgress);
if (respData) {
// If there is a total, save to the total variable
if (respData['total']) {
total = respData.total;
// If there is a progress, display progress to the client
} else if (respData['progress']) {
const { progress } = respData;
const percent = (progress / total) * 100;
progEl.textContent = `${respData['progress']} of ${total} (${percent.toFixed(1)}%)`;
const timeSpan = (new Date) - timeStart;
timeEl.textContent = `${timeSpan / 1000} s`;
// Elese if there is an img_url, we've finished
} else if (respData['img_url']) {
progEl.textContent = `Done! Displaying image: "${respData['img_url']}"`;
}
}
});
xhr.addEventListener('loadend', function(e) {
btnEl.disabled = false;
});
xhr.open("GET", '/compute-image');
xhr.send();
});
Demo client screen capture:
You can find the demo project in this Github repository: https://github.com/clytras/py-flask-ajax-progress
I try to build a web app which makes video process and send processed video back with the code below.The process funtions do this job byte by byte so we have that data which are file size and byte remaining
I am using that code block to let the users download a file -serverside
#app.route('/file',methods = ['POST', 'GET'])
def file():
video process functions
def generate():
try:
f=open(path,"rb")
yield from f
finally:
f.close()
os.remove(path)
r = app.response_class(generate(), mimetype='audio/mp3',
content_type="audio")
r.headers.set('Content-Disposition', 'attachment', filename=filename)
r.set_cookie('ho',value='values')
return r
There is a simple form
<form id="you-form" action="{{url_for('file')}}" method="GET">
the codes work fine but the app can calculate how much remaining while makin video process so ı want to show this clint with progress bar.
If you need more information please ask
Thanks for help in advance
I am writing a preview portion for video management system, it works like a charm in chrome with standard tag but firefox does not recognize MIME type for some reason and it bugs me a lot.
Here is my stream class:
class Stream:
run = False
FNULL = open(os.devnull, 'w')
overlay = ffmpeg.input("somelogo.png")
def __init__(self, camid):
camUtil = CameraUtil()
self.camid = camid
self.streamurl = camUtil.get_stream_from_id(self.camid)['streamURL']
print(self.streamurl)
self.args = ffmpeg.input(self.streamurl)
# vcodec="libvpx",
# acodec="libvorbis",
self.args = ffmpeg.output(self.args, "-",
f="matroska",
vcodec="copy",
acodec="copy",
blocksize="1024",
# strftime="1",
# segment_time="60",
# segment_format="matroska"
preset="ultrafast",
metadata="title='test'"
)
self.args = ffmpeg.get_args(self.args)
print(self.args)
self.pipe = subprocess.Popen(['ffmpeg'] + self.args,
stdout=subprocess.PIPE,)
#stderr=self.FNULL)
def dep_stream(self):
def gen():
try:
f = self.pipe.stdout
byte = f.read(1024)
while byte:
yield byte
byte = f.read(1024)
finally:
self.pipe.kill()
return Response(gen(), status=200,
mimetype='video/webm',
headers={'Access-Control-Allow-Origin': '*',
"Content-Type": "video/webm",
})
My html playback portion:
<video id="live_page_player" id="video" preload="auto" autoplay width="1280" height="720">
<source src="/stream/{{ camid }}" type='video/webm;codecs="vp8, vorbis"'/>
YOUR BROWSER DOES NOT SUPPORT HTML5, WHAT YEAR ARE YOU FROM?!
</video>
Firefox says "No video with supported format and MIME type found" and in console it says
error: Error Code: NS_ERROR_DOM_MEDIA_METADATA_ERR (0x806e0006)
Did I do something dumb?! Or am I missing something, because it works google chrome like a charm
I need fresh eyes.
Help plez
So after bashing my head around, I decided to check out the console(yes I know)
I found that firefox throws NS_ERROR_DOM_MEDIA_METADATA_ERR, after vigorous googling I have found that raw matroska is not supported by firefox(or rather they don't let you play it for some reason) while google chrome does support it.
The solution was actually pretty simple, you gotta re-encode the stream with vcodec libvpx-vp9 or vp8 and acoded libopus or libvorbis
The ffmpeg for python syntax would look like this:
self.args = ffmpeg.output(self.args, "-",
f="webm",
vcodec="libvpx-vp9",
acodec="loboupus",
blocksize="1024",
# strftime="1",
# segment_time="60",
# segment_format="matroska"
preset="ultrafast",
metadata="title='test'"
)
Note that this eats the CPU quite heavily, Im still playing around with it but this is the solution!
I want to stream the audio of my microphone (that is being recorded via pyaudio) via Flask to any client that connects.
This is where the audio comes from:
def getSound(self):
# Current chunk of audio data
data = self.stream.read(self.CHUNK)
self.frames.append(data)
wave = self.save(list(self.frames))
return data
Here's my flask-code:
#app.route('/audiofeed')
def audiofeed():
def gen(microphone):
while True:
sound = microphone.getSound()
#with open('tmp.wav', 'rb') as myfile:
# yield myfile.read()
yield sound
return Response(stream_with_context(gen(Microphone())))
And this is the client:
<audio controls>
<source src="{{ url_for('audiofeed') }}" type="audio/x-wav;codec=pcm">
Your browser does not support the audio element.
</audio>
It does work sometimes, but most of the times I'm getting "[Errno 32] Broken pipe"
When uncommenting that with open("tmp.wav")-part (the self.save() optionally takes all previous frames and saves them in tmp.wav), I kind of get a stream, but all that comes out of the speakers is a "clicking"-noise.
I'm open for any suggestions. How do I get the input of my microphone live-streamed (no pre-recording!) to a webbrowser?
Thanks!
Try This its worked for me. shell cmd "cat" is working perfect see the code
iam using FLASK
import subprocess
import os
import inspect
from flask import Flask
from flask import Response
#app.route('/playaudio')
def playaudio():
sendFileName=""
def generate():
# get_list_all_files_name this function gives all internal files inside the folder
filesAudios=get_list_all_files_name(currentDir+"/streamingAudios/1")
# audioPath is audio file path in system
for audioPath in filesAudios:
data=subprocess.check_output(['cat',audioPath])
yield data
return Response(generate(), mimetype='audio/mp3')
This question was asked long time ago, but since I spent entire day to figure out how to implement the same, I want to give the answer. Maybe it will be helpful for somebody.
"[Errno 32] Broken pipe" error comes from the fact that client can not play audio and closes this stream.
Audio can not be played due to absence of the header in the data stream. You can easily create the header using genHeader(sampleRate, bitsPerSample, channels, samples) function from the code here . This header has to be attached at least to the first chunck of sent data ( chunck=header+data ). Pay attention, that audio can be played ONLY untill client reaches file size in download that you have to specify in the header. So, workaround would be to set in the header some big files size, e.g. 2Gb.
Instead of datasize = len(samples) * channels * bitsPerSample in the header function write datasize = 2000*10**6.
def gen_audio():
CHUNK = 512
sampleRate = 44100
bitsPerSample = 16
channels = 2
wav_header = genHeader(sampleRate, bitsPerSample, channels)
audio = AudioRead()
data = audio.get_audio_chunck()
chunck = wav_header + data
while True:
yield (chunck)
data = audio.get_audio_chunck()
chunck = data
After lots research and tinkering I finally found the solution.
Basically it came down to serving pyaudio.paFloat32 audio data through WebSockets using Flask's SocketIO implementation and receiving/playing the data in JavaScript using HTML5's AudioContext.
As this is requires quite some code, I think it would not be a good idea to post it all here. Instead, feel free to check out the project I'm using it in: simpleCam
The relevant code is in:
- noise_detector.py (recording)
- server.py (WebSocket transfer)
- static/js/player.js (receiving/playing)
Thanks everyone for the support!
I am attempting to implement a flask application for uploading files. This file could be very large. For example, almost 2G in size.
I have finished the server side process function like this:
#app.route("/upload/<filename>", methods=["POST", "PUT"])
def upload_process(filename):
filename = secure_filename(filename)
fileFullPath = os.path.join(application.config['UPLOAD_FOLDER'], filename)
with open(fileFullPath, "wb") as f:
chunk_size = 4096
while True:
chunk = flask.request.stream.read(chunk_size)
if len(chunk) == 0:
return
f.write(chunk)
return jsonify({'filename': filename})
As for browser side, I should give users a from to submit the file. One file at a time. Show progressbar to indicate the uploading process.
But I have no idea about the browser side code. How can I use javascript code to start the uploading and show it status?
This will be a difficult task for your to figure out on your own. I would suggest a plugin like https://blueimp.github.io/jQuery-File-Upload/
You can see from this projects source code they use a method name which essentially looks at how large the file is and how much data has been transferred thus far and how much remains to show a percentage complete div.
code example from this project
progressall: function (e, data) {
var $this = $(this);
$this.find('.fileupload-progress')
.find('.progress').progressbar(
'option',
'value',
parseInt(data.loaded / data.total * 100, 10)
).end()
.find('.progress-extended').each(function () {
$(this).html(
($this.data('blueimp-fileupload') ||
$this.data('fileupload'))
._renderExtendedProgress(data)
);
});
}
https://github.com/blueimp/jQuery-File-Upload/blob/master/js/jquery.fileupload-jquery-ui.js
So if you do want to come up with your own solution, I would suggest you start by building a UI div rectangle which has a dynamic width which updates according to your percentage calculation based upon the file upload size and data uploaded... or just go with an already established solution.