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Python’s New Structural Pattern Matching!

It’s finally happened, after years of complaining and told “it will never happen”, I got my darn switch statement! And honestly, calling it only a “switch” statement is really underselling it. It’s much more powerful than most people will ever use! You might have already heard about this, but I wanted to make sure it made it to at least the 3.10 beta phase, as the alphas are no guarantee you’ll actually see the new feature (still possible to remove before the RC phase, but less likely).

Artwork by Clara Griffith

Python 3.10 will introduce “Structural Pattern Matching” as introduced in PEP622 which is a crazy advanced switch statement that can recognizing patterns. Instead of the keyword switch Python will introduce match instead (get ready to update your regex variable names!). Let’s do a little quick compare with it and JavaScript’s switch statement. First let’s start off with the Javascript example modified from w3schools.

Javascript’s Switch

switch (new Date().getDay()) {
  case 5:
    console.log("It's Friday!");
    break;
  case 0:
  case 6:
    console.log("Woo, Weekend!");
    break;
  default:
    console.log("Work. Work. Work. Work.");
}

Python’s Structural Pattern Matching

We can accomplish the same with Python in less lines. Note that in Python the weekday starts at 0 for Monday.

from datetime import datetime

match datetime.today().weekday():  
    case 4:
        print("It's Friday!")
    case 5 | 6:
        print("Woo, Weekend!")
    case _:
        print("Work. Work. Work. Work.")

Similarities and Differences

With Python’s new match style statements, the biggest change from tradition is no “drop through” cases. Aka you don’t have to manually specify break or anything to exit the match case for every instance. That does mean though that you can’t have multiple matches with the same result. Instead you can combine checks with | for “or” operations. Which I honestly think is a lot cleaner.

What I don’t like is there is no default keyword or similar, and you have to use the _ wildcard. The underscore is already overused in my opinion. However it does add a lot of power for more advanced cases. Let’s dive into some more examples.

Matching and Assigning

The very basic things to understand about the new Structural Pattern Matching is the flow (as seen in the example above) and the possibility of assignment. Because not only can you make sure things are equal to another literal, you can detect patterns (as the name suggests) and then work with the variables inside the pattern itself.

Pattern Recognition

Lets dip the toes in on this whole “pattern matching” thing, what does that mean?

Say you have a tuple with two objects, that could be in either order and you always want to print it right.

data_1 = ("Purchase Number", 574)
data_2 = (574, "Purchase Number")

You could have a simple match case to straighten it out so it always prints “Purchase Number 574”. As the pattern matching support type checking.

match data_1:
    case str(x), int(y):
        print(x, y) 
    case int(x), str(y):
        print(y, x)

Match on dict values

Just like with regular value comparisons, you can check dictionary values and still do or operations. In this case, either grade b or c will print out "Welcome to being average!"

match {'grade': 'B'}:
    case {'grade': 'a' | 'A'}:
        print("You're a star!")
    case {'grade': 'b' | 'c' | 'B' | 'C'}:
        print("Welcome to being average!")

Unpacking arbitrary data

You can use the standard * and ** unpackers to capture and unpack variable length lists and dicts.

my_dict = {'data': [{'action': 'move'}, {'action': 'stay'}],
           'location': "square_10"}

match my_dict:
    case {'data': [*options], **remainder }:
        print(options)
        print(remainder)
    case _:
        raise ValueError("Data not as expected")

Will match with the first case and print out:

[{'action': 'move'}, {'action': 'stay'}]
{'location': 'square_10'}

That can really come in handy if dealing with variable length data.

Adding the “if”

You can also add in some inline checks.

cords = (30.25100365332043, -97.86221371827051, "Workplace")
cords_2 = (44.40575746530253, 8.947747627912994)

match cords: 
    case lat, lon, *_ if lat > 0:
        print("Northern Hemisphere")
    case lat, lon, *_ if lat < 0: 
        print("Sothern Hemisphere")    

Don’t forget about “as”

Sometimes you might want one the many literals you are looking for to be usable in the case itself. Lets put a lot of our knowledge together and check out the added power of the as clause.

We are going to build a really simple command line game to look for random things.

import sys
import random

inventory = []

while True:
    match input().lower().split():
        # Remember `split` makes the input into a list.  
        # These first two cases are functionally the same.
        case ["exit"]:  
            sys.exit(0)
        case "stop", *_: 
            sys.exit(0)
        case "travel", "up" | "down" | "left" | "right" as direction:
            print(f"Going {direction}")
        case "search", "area" | "backpack" as thing, _, *extra:
            item = " ".join(extra)
            if thing == "backpack":
               if item  in inventory:
                   print(f"Yes you have {item}")
               else:
                   print(f"No you don't have {item}")
            elif thing == "area":
                 if random.randint(1, 10) > 5:
                     inventory.append(item)
                     print(f"You found {item}!")
                 else:
                    print(f"No {item} here")
            else:
                print(f"Sorry, you cannot search {thing}")
        case _:
            print("sorry, didn't understand you! type 'exit' or 'stop' to quit")

Lets do a quick playthrough:

> search area for diamonds
You found diamonds!

> search backpack for diamonds
Yes you have diamonds

> take a short rest and try to eat the diamonds
sorry, didn't understand you! type 'exit' or 'stop' to quit

> Travel Up
Going up

> search area for candy
No candy here

> search backpack for candy
No you don't have candy

> stop
# Process finished with exit code 0

Notice our special case for searching around.

case "search", "area" | "backpack" as thing, _, *extra:

we are looking for the first keyword “Search”, then either “area” or “backpack” and saving which to the variable thing. The _ will ignore the next word as we expect them to type for or something useless there. Finally we grab everything else and treat it as a single item.

Classes and More

Using dataclasses with match is super easy.

from dataclasses import dataclass

@dataclass
class Car:
    model: str
    top_speed: int

car_1 = Car("Jaguar F-Type R", 186)
car_2 = Car("Tesla Model S", 163)
car_3 = Car("BMW M4", 155)

match car_1:
    case Car(x, speed) if speed > 180:
        print(f"{x} is a super fast car!")
    case Car(x, speed) if speed > 160:
        print(f"{x} is a pretty fast car")
    case _:
        print("Regular Car")

Using a regular class, you have to be a pit more explicit about the varaibles that are being used.

class Car:

    def __init__(self, model, top_speed):
        self.model = model
        self.top_speed = top_speed


car_1 = Car("F-Type R", 186)
car_2 = Car("Model S", 163)
car_3 = Car("BMW M4", 155)

match car_1:
    case Car(model=x, top_speed=speed) if speed > 180:
        print(f"{x} is a super fast car!")
    case Car(model=x, top_speed=speed) if speed > 160:
        print(f"{x} is a pretty fast car")
    case _:
        print("Regular Car")

However, there is a way around that! You can add __match_args__ to the class itself to define which arguments you will want to use for the pattern recognition.

class Car:

    __match_args__ = ["model", "top_speed"]
    def __init__(self, model, top_speed):
        self.model = model
        self.top_speed = top_speed


car_1 = Car("F-Type R", 186)
car_2 = Car("Model S", 163)
car_3 = Car("BMW M4", 155)

match car_1:
    case Car(x, speed) if speed > 180:
        print(f"{x} is a super fast car!")
    case Car(x, speed) if speed > 160:
        print(f"{x} is a pretty fast car")
    case _:
        print("Regular Car")

Summary

Structural Pattern Matching is Python’s sexy new “switch” statement that will bring a lot of power, and removal of a lot of old if elif blocks. The only real downside is that it’s brand new, and will take a few years for most people to be able to use it with their default interpreter.

Stop Re-Encoding Videos!

I know this may sound like a weird statement coming from the author of FastFlix, but from the bottom of my heart, please stop the needless pixel loss! Every time you re-encode (aka transcode) a video it losses information, which lowers the quality and makes it a lot worse if you ever need to do it again. Re-encoding makes you a pixel killer!

Why am I saying re-encoding and not just “encoding” when you may have the original video? Sadly, to even fit onto your computer or device the video you are working with has already been encoded in a highly compressed manor. Even phones and professional cameras like the RED series use real-time compression. Raw video takes too much bandwidth for standard storage media. For example, imaging recording raw video using a video sensor at 16-bit 60FPS. A single minute of UHD footage would be near 60GB! That translates into a bitrate of over 7,500,000 kbps. Compare that to a re-encoded YouTube video of HDR 60FPS 4K footage is around 30,000 kbps, 250x times less quality!

Why does it matter?

Everyone has seen potato quality images and videos being re-shared again and again. The quality loss is due to needless re-encoding.

Websites generally always re-encode videos for a variety of reasons, such as adding watermarks or forcing certain bitrates. It may be required in some instances, but for most cases it’s overkill. If I had the power I would challenge websites to instead publish what encoding targets are required and allow for direct playback of the original file.

But while we don’t have control over that, that makes it even more important to not make it worse when you have control over it.

In the above example I took a short video and encoded it again and again and again using the same settings each time. The video still looks good while being watched, but if you zoom in you can see the entire thing has essentially become blurred. Don’t do this to your own videos, save the pixels!

Future Proofing

Another thing to consider is not just the result you have now, but how it will look in ten or twenty years. Sure, the single 1080p or 4K re-encode you did now may look perfect. But what about when 16K TVs are standard? What about when your phone or monitors pixel density is four to eight times higher than it is now? Behind the scenes of good TVs and devices is an “Ai” chip that upscales videos to look better on newer screens. With less detail to start with, it won’t look as good as if you didn’t re-encode.

Remember that amazing video you took with your flip phone all those years ago that you can’t even tell what is happening in it anymore? You don’t want that to happen to your videos now.

There are some cases that it cannot be avoided that we will cover later, but even common operations like trimming videos and rotating them can be accomplished without re-encoding.

Trim and Rotate without re-encoding

Two very common reasons people want to re-encode videos is to shorten them to a particular section, or rotate it the proper direction. Thankfully you can do both of those without modifying the original video stream. I am using the command line tool ffmpeg to accomplish this, which is available for free.

Rotate

To rotate the video, you just have to add some metadata to the container the video is in. This is how phones set videos to portrait or landscape mode without having to change their encoder settings.

ffmpeg -i your_video.mp4 -metadata 0:s:v rotate=90 -map 0 -c copy rotated_video.mp4

In the above example, replace your_video.mp4 with the video file you need rotated. It will be copied with the new metadata to rotated_video.mp4 and now should be rotated properly.

Trim

To cut out a section of the video, you simply need to “copy” everything between the two desired points. For example if you want to cut out a 48 second section between 1:02 and 1:50 (one minute two seconds and one minute fifty seconds), use the following command.

ffmpeg --ss 1:02 -to 1:50  -i your_video.mp4 -map 0 -c copy rotated_video.mp4

Are there any exceptions?

There are a few cases where you simply cannot avoid re-encoding. If you need to add effects, crop, make any actual modifications to the video, you will need to re-encode.

However if you are keeping the video as is, there are only three instances you should consider re-encoding for:

  • Limited bandwidth scenarios
  • Device compatibility
  • Cannot provide required storage space

Limited bandwidth scenario

ISPs still like to pretend upload speeds don’t matter. Even if an ISP provides 1Gbps down most still have less than 45Mbps upload peak. Things get even worse for mobile, where the average upload rate is around 10Mbps. Then on top of that, a general rule of thumb is your video bitrate should be around half or less of available bandwidth to ensure there isn’t stuttering.

That means if you’re planning to share videos in real time with the world, you simply have to re-encode (transcode) it.

Device compatibility

There are some large companies that have terrible compatibility with commonly accepted formats to be anti-competition. That means if you or a loved one is enslaved to some large fruit company, you may need to tinker with your videos to please the orchard overlords.

Storage space

“Storage is cheap” is a phrase I hear a little too much in the coding world. In the real world without a large quarterly tech budget, you have to count your pennies. If you can re-encode a video so that it’s near visually lossless while saving on storage space for your needs, go for it!

Upload large files fast with Dropzone.js

I have previously covered how to upload large files with dropzone.js, but it didn’t allow for parallel chunk uploads. In this article we will go over that new addition, as well as several other improvements.

Download the final executable or view github to see all the code now if you don’t want to read the article.

This is the final result for now, and can be customized if you so chose. Obviously I’m no graphic design, but I’d pick function over style anyway.

Design

Before we dive into code, lets think about the design. We will need to somehow handle multiple parts of a single file being uploaded at the same time in a random order. How do we keep track of that?

Thankfully, Dropzone will provide the server with a few different pieces of information which each chunk, they include:

  • dzuuid – unique ID per upload file
  • dzchunkindex – the chunk number of the current upload
  • dztotalfilesize – Total size of the upload
  • dzchunksize – Max size per chunk
  • dztotalchunkcount – The number of chunks in this file
  • dzchunkbyteoffset – The place in the file this chunk starts

In my mind there are two clear ways to approach the problem. First option is to create a sparse file of the full size to start with, using dztotalchunkcount and then with every incoming chunk, set the position of the file using dzchunkbyteoffset and write the data starting there.

The advantage of this method is that it only requires a single file on disk. The disadvantage is you have to worry about multiple threads accessing the same file at the same time.

The second choice is to write each chunk to a separate file, then when they are all uploaded concatenate them all to a single file and remove the individual chunks. The disadvantage are that that you require twice the space for a short time, and have to deal with cleanup of temporary files.

I personally preferred the second option, as it seemed a bit safer.

Upload Function

As a quick warning, I am now using Bottle instead of Flask for this upload, so a bit of the form syntax has changed since the last post.

from pathlib import Path
from threading import Lock
from collections import defaultdict
import shutil
import uuid

from bottle import route, run, request, error, response, HTTPError, static_file
from werkzeug.utils import secure_filename

lock = Lock()
chucks = defaultdict(list)

chunk_path = Path(__file__).parent / "chunks"
storage_path = Path(__file__).parent / "storage"
chunk_path.mkdir(exist_ok=True, parents=True)
storage_path.mkdir(exist_ok=True, parents=True)

@route("/upload", method="POST")
def upload():
    file = request.files.get("file")
    if not file:
        raise HTTPError(status=400, body="No file provided")

    dz_uuid = request.forms.get("dzuuid")
    if not dz_uuid:
        # Assume this file has not been chunked
        with open(storage_path / f"{uuid.uuid4()}_{secure_filename(file.filename)}", "wb") as f:
            file.save(f)
        return "File Saved"

    # Chunked download
    try:
        current_chunk = int(request.forms["dzchunkindex"])
        total_chunks = int(request.forms["dztotalchunkcount"])
    except KeyError as err:
        raise HTTPError(status=400, body=f"Not all required fields supplied, missing {err}")
    except ValueError:
        raise HTTPError(status=400, body=f"Values provided were not in expected format")
    
    # Create a new directory for this file in the chunks dir, using the UUID as the folder name
    save_dir = chunk_path / dz_uuid
    if not save_dir.exists():
        save_dir.mkdir(exist_ok=True, parents=True)

    # Save the individual chunk
    with open(save_dir / str(request.forms["dzchunkindex"]), "wb") as f:
        file.save(f)

    # See if we have all the chunks downloaded
    with lock:
        chucks[dz_uuid].append(current_chunk)
        completed = len(chucks[dz_uuid]) == total_chunks

    # Concat all the files into the final file when all are downloaded
    if completed:
        with open(storage_path / f"{dz_uuid}_{secure_filename(file.filename)}", "wb") as f:
            for file_number in range(total_chunks):
                f.write((save_dir / str(file_number)).read_bytes())
        print(f"{file.filename} has been uploaded")
        shutil.rmtree(save_dir)

    return "Chunk upload successful"

if __name__ == "__main__":
    run(server="paste")

Hopefully the code is decently self documented. We do a few checks at the start as we pull in the required parameters. Then we prepare the directory for where the temporary chunks will be stored, and write the incoming chunk there. We gather information on all the chunks and when then have been completed in a global dictionary, and when they are all uploaded they are assembled into the final file.

File Downloading

Now that we can put files on the server, what about getting them back? I personally don’t want people to host random files on my server, but others may. To accomplish that, we shouldn’t just list all the files to everyone that visits the site, but only to whoever uploaded it. Thankfully we can just store the uuid in a cookie on the frontend, and then have a very basic download function.

@route("/download/<dz_uuid>")
def download(dz_uuid):
    for file in storage_path.iterdir():
        if file.is_file() and file.name.startswith(dz_uuid):
            return static_file(file.name, root=file.parent.absolute(), download=True)
    return HTTPError(status=404)

This does complicate our frontend a bit, as we want to save both UUID and filename as text fields in a cookie. There are a lot of great libraries out there to make life easier with JavaScript and cookies, but I wanted to keep it simple and pure JS other than Dropzone, making the code a bit more complicated than last time.

Dropzone frontend

Instead of being a standalone file, I have also put this directly into the python file to make using it as a f-string a lot easier, but makes it a little harder to read.

<!doctype html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <link rel="stylesheet" href="{dropzone_cdn.rstrip('/')}/{dropzone_version}/min/dropzone.min.css"/>
    <link rel="stylesheet" href="{dropzone_cdn.rstrip('/')}/{dropzone_version}/min/basic.min.css"/>
    <script type="application/javascript"
        src="{dropzone_cdn.rstrip('/')}/{dropzone_version}/min/dropzone.min.js">
    </script>
    <title>pyfiledrop</title>
</head>
<body>

    <div id="content" style="width: 800px; margin: 0 auto;">
        <h2>Upload new files</h2>
        <form method="POST" action='/upload' class="dropzone dz-clickable" id="dropper" enctype="multipart/form-data">
        </form>

        <h2>
            Uploaded
            <input type="button" value="Clear" onclick="clearCookies()" />
        </h2>
        <div id="uploaded">

        </div>

        <script type="application/javascript">
            function clearCookies() {{
                document.cookie = "files=; Max-Age=0";
                document.getElementById("uploaded").innerHTML = "";
            }}

            function getFilesFromCookie() {{
                try {{ return document.cookie.split("=", 2)[1].split("||");}} catch (error) {{ return []; }}
            }}

            function saveCookie(new_file) {{
                    let all_files = getFilesFromCookie();
                    all_files.push(new_file);
                    document.cookie = `files=${{all_files.join("||")}}`;
            }}

            function generateLink(combo){{
                const uuid = combo.split('|^^|')[0];
                const name = combo.split('|^^|')[1];
                if ({'true' if allow_downloads else 'false'}) {{
                    return `<a href="/download/${{uuid}}" download="${{name}}">${{name}}</a>`;
                }}
                return name;
            }}


            function init() {{

                Dropzone.options.dropper = {{
                    paramName: 'file',
                    chunking: true,
                    forceChunking: {dropzone_force_chunking},
                    url: '/upload',
                    retryChunks: true,
                    parallelChunkUploads: {dropzone_parallel_chunks},
                    timeout: {dropzone_timeout}, // microseconds
                    maxFilesize: {dropzone_max_file_size}, // megabytes
                    chunkSize: {dropzone_chunk_size}, // bytes
                    init: function () {{
                        this.on("complete", function (file) {{
                            let combo = `${{file.upload.uuid}}|^^|${{file.upload.filename}}`;
                            saveCookie(combo);
                            document.getElementById("uploaded").innerHTML += generateLink(combo)  + "<br />";
                        }});
                    }}
                }}

                if (typeof document.cookie !== 'undefined' ) {{
                    let content = "";
                     getFilesFromCookie().forEach(function (combo) {{
                        content += generateLink(combo) + "<br />";
                    }});

                    document.getElementById("uploaded").innerHTML = content;
                }}
            }}

            init();

        </script>
    </div>
</body>
</html>

Notice we are using a slew of python variables that we are going to allow to be configurable upon launch.

Command line options

import argparse
...

allow_downloads = False
dropzone_cdn = "https://cdnjs.cloudflare.com/ajax/libs/dropzone"
dropzone_version = "5.7.6"
dropzone_timeout = "120000"
dropzone_max_file_size = "100000"
dropzone_chunk_size = "1000000"
dropzone_parallel_chunks = "true"
dropzone_force_chunking = "true"

...


def parse_args():
    parser = argparse.ArgumentParser()
    parser.add_argument("-p", "--port", type=int, default=16273, required=False)
    parser.add_argument("--host", type=str, default="0.0.0.0", required=False)
    parser.add_argument("-s", "--storage", type=str, default=str(storage_path), required=False)
    parser.add_argument("-c", "--chunks", type=str, default=str(chunk_path), required=False)
    parser.add_argument(
        "--max-size",
        type=str,
        default=dropzone_max_file_size,
        help="Max file size (Mb)",
    )
    parser.add_argument(
        "--timeout",
        type=str,
        default=dropzone_timeout,
        help="Timeout (ms) for each chuck upload",
    )
    parser.add_argument("--chunk-size", type=str, default=dropzone_chunk_size, help="Chunk size (bytes)")
    parser.add_argument("--disable-parallel-chunks", required=False, default=False, action="store_true")
    parser.add_argument("--disable-force-chunking", required=False, default=False, action="store_true")
    parser.add_argument("-a", "--allow-downloads", required=False, default=False, action="store_true")
    parser.add_argument("--dz-cdn", type=str, default=None, required=False)
    parser.add_argument("--dz-version", type=str, default=None, required=False)
    return parser.parse_args()


if __name__ == "__main__":

    args = parse_args()
    storage_path = Path(args.storage)
    chunk_path = Path(args.chunks)
    dropzone_chunk_size = args.chunk_size
    dropzone_timeout = args.timeout
    dropzone_max_file_size = args.max_size
    try:
        if int(dropzone_timeout) < 1 or int(dropzone_chunk_size) < 1 or int(dropzone_max_file_size) < 1:
            raise Exception("Invalid dropzone option, make sure max-size, timeout, and chunk-size are all positive")
    except ValueError:
        raise Exception("Invalid dropzone option, make sure max-size, timeout, and chunk-size are all integers")

    if args.dz_cdn:
        dropzone_cdn = args.dz_cdn
    if args.dz_version:
        dropzone_version = args.dz_version
    if args.disable_parallel_chunks:
        dropzone_parallel_chunks = "false"
    if args.disable_force_chunking:
        dropzone_force_chunking = "false"
    if args.allow_downloads:
        allow_downloads = True

    if not storage_path.exists():
        storage_path.mkdir(exist_ok=True)
    if not chunk_path.exists():
        chunk_path.mkdir(exist_ok=True)

    print(f"""Timeout: {int(dropzone_timeout) // 1000} seconds per chunk
Chunk Size: {int(dropzone_chunk_size) // 1024} Kb
Max File Size: {int(dropzone_max_file_size)} Mb
Force Chunking: {dropzone_force_chunking}
Parallel Chunks: {dropzone_parallel_chunks}
Storage Path: {storage_path.absolute()}
Chunk Path: {chunk_path.absolute()}
""")
    run(server="paste", port=args.port, host=args.host)

As this will become an executable, to be configurable we want to pass parameters upon launch.

Favicon

Now this is getting into the realm of silly. But to be an all in one script, we need to provide a binary file (the favicon) in the script itself. Thankfully ico files can be compressed rather easily, so we are going to compress it in the script itself, and decompress it when requested.

@route("/favicon.ico")
def favicon():
    return zlib.decompress(
        b"x\x9c\xedVYN\xc40\x0c5J%[\xe2\xa3|q\x06\x8e1G\xe1(=ZoV"
        b"\xb2\xa7\x89\x97R\x8d\x84\x04\xe4\xa5\xcb(\xc9\xb3\x1do"
        b"\x1d\x80\x17?\x1e\x0f\xf0O\x82\xcfw\x00\x7f\xc1\x87\xbf"
        b"\xfd\x14l\x90\xe6#\xde@\xc1\x966n[z\x85\x11\xa6\xfcc"
        b"\xdfw?s\xc4\x0b\x8e#\xbd\xc2\x08S\xe1111\xf1k\xb1NL"
        b"\xfcU<\x99\xe4T\xf8\xf43|\xaa\x18\xf8\xc3\xbaHFw\xaaj\x94"
        b"\xf4c[F\xc6\xee\xbb\xc2\xc0\x17\xf6\xf4\x12\x160\xf9"
        b"\xa3\xfeQB5\xab@\xf4\x1f\xa55r\xf9\xa4KGG\xee\x16\xdd\xff"
        b"\x8e\x9d\x8by\xc4\xe4\x17\tU\xbdDg\xf1\xeb\xf0Zh\x8e"
        b"\xd3s\x9c\xab\xc3P\n<e\xcb$\x05 b\xd8\x84Q1\x8a\xd6Kt\xe6"
        b"\x85(\x13\xe5\xf3]j\xcf\x06\x88\xe6K\x02\x84\x18\x90"
        b"\xc5\xa7Kz\xd4\x11\xeeEZK\x012\xe9\xab\xa5\xbf\xb3@i\x00"
        b"\xce\xe47\x0b\xb4\xfe\xb1d\xffk\xebh\xd3\xa3\xfd\xa4:`5J"
        b"\xa3\xf1\xf5\xf4\xcf\x02tz\x8c_\xd2\xa1\xee\xe1\xad"
        b"\xaa\xb7n-\xe5\xafoSQ\x14'\x01\xb7\x9b<\x15~\x0e\xf4b"
        b"\x8a\x90k\x8c\xdaO\xfb\x18<H\x9d\xdfj\xab\xd0\xb43\xe1"
        b'\xe3nt\x16\xdf\r\xe6\xa1d\xad\xd0\xc9z\x03"\xc7c\x94v'
        b"\xb6I\xe1\x8f\xf5,\xaa2\x93}\x90\xe0\x94\x1d\xd2\xfcY~f"
        b"\xab\r\xc1\xc8\xc4\xe4\x1f\xed\x03\x1e`\xd6\x02\xda\xc7k"
        b"\x16\x1a\xf4\xcb2Q\x05\xa0\xe6\xb4\x1e\xa4\x84\xc6"
        b"\xcc..`8'\x9a\xc9-\n\xa8\x05]?\xa3\xdfn\x11-\xcc\x0b"
        b"\xb4\x7f67:\x0c\xcf\xd5\xbb\xfd\x89\x9ebG\xf8:\x8bG"
        b"\xc0\xfb\x9dm\xe2\xdf\x80g\xea\xc4\xc45\xbe\x00\x03\xe9\xd6\xbb"
    )

Putting it all together

Here is the culmination of everything we talked about put into a script.

This may not always be the newest version, if you want to use it yourself please download the final executable or view github to see the latest code.

#!/usr/bin/env python
# -*- coding: utf-8 -*-
from pathlib import Path
from threading import Lock
from collections import defaultdict
import shutil
import argparse
import uuid
import zlib

from bottle import route, run, request, error, response, HTTPError, static_file
from werkzeug.utils import secure_filename

storage_path: Path = Path(__file__).parent / "storage"
chunk_path: Path = Path(__file__).parent / "chunk"

allow_downloads = False
dropzone_cdn = "https://cdnjs.cloudflare.com/ajax/libs/dropzone"
dropzone_version = "5.7.6"
dropzone_timeout = "120000"
dropzone_max_file_size = "100000"
dropzone_chunk_size = "1000000"
dropzone_parallel_chunks = "true"
dropzone_force_chunking = "true"

lock = Lock()
chucks = defaultdict(list)


@error(500)
def handle_500(error_message):
    response.status = 500
    response.body = f"Error: {error_message}"
    return response


@route("/")
def index():
    index_file = Path(__file__) / "index.html"
    if index_file.exists():
        return index_file.read_text()
    return f"""
<!doctype html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <link rel="stylesheet" href="{dropzone_cdn.rstrip('/')}/{dropzone_version}/min/dropzone.min.css"/>
    <link rel="stylesheet" href="{dropzone_cdn.rstrip('/')}/{dropzone_version}/min/basic.min.css"/>
    <script type="application/javascript"
        src="{dropzone_cdn.rstrip('/')}/{dropzone_version}/min/dropzone.min.js">
    </script>
    <title>pyfiledrop</title>
</head>
<body>

    <div id="content" style="width: 800px; margin: 0 auto;">
        <h2>Upload new files</h2>
        <form method="POST" action='/upload' class="dropzone dz-clickable" id="dropper" enctype="multipart/form-data">
        </form>

        <h2>
            Uploaded
            <input type="button" value="Clear" onclick="clearCookies()" />
        </h2>
        <div id="uploaded">

        </div>

        <script type="application/javascript">
            function clearCookies() {{
                document.cookie = "files=; Max-Age=0";
                document.getElementById("uploaded").innerHTML = "";
            }}

            function getFilesFromCookie() {{
                try {{ return document.cookie.split("=", 2)[1].split("||");}} catch (error) {{ return []; }}
            }}

            function saveCookie(new_file) {{
                    let all_files = getFilesFromCookie();
                    all_files.push(new_file);
                    document.cookie = `files=${{all_files.join("||")}}`;
            }}

            function generateLink(combo){{
                const uuid = combo.split('|^^|')[0];
                const name = combo.split('|^^|')[1];
                if ({'true' if allow_downloads else 'false'}) {{
                    return `<a href="/download/${{uuid}}" download="${{name}}">${{name}}</a>`;
                }}
                return name;
            }}


            function init() {{

                Dropzone.options.dropper = {{
                    paramName: 'file',
                    chunking: true,
                    forceChunking: {dropzone_force_chunking},
                    url: '/upload',
                    retryChunks: true,
                    parallelChunkUploads: {dropzone_parallel_chunks},
                    timeout: {dropzone_timeout}, // microseconds
                    maxFilesize: {dropzone_max_file_size}, // megabytes
                    chunkSize: {dropzone_chunk_size}, // bytes
                    init: function () {{
                        this.on("complete", function (file) {{
                            let combo = `${{file.upload.uuid}}|^^|${{file.upload.filename}}`;
                            saveCookie(combo);
                            document.getElementById("uploaded").innerHTML += generateLink(combo)  + "<br />";
                        }});
                    }}
                }}

                if (typeof document.cookie !== 'undefined' ) {{
                    let content = "";
                     getFilesFromCookie().forEach(function (combo) {{
                        content += generateLink(combo) + "<br />";
                    }});

                    document.getElementById("uploaded").innerHTML = content;
                }}
            }}

            init();

        </script>
    </div>
</body>
</html>
    """


@route("/favicon.ico")
def favicon():
    return zlib.decompress(
        b"x\x9c\xedVYN\xc40\x0c5J%[\xe2\xa3|q\x06\x8e1G\xe1(=ZoV"
        b"\xb2\xa7\x89\x97R\x8d\x84\x04\xe4\xa5\xcb(\xc9\xb3\x1do"
        b"\x1d\x80\x17?\x1e\x0f\xf0O\x82\xcfw\x00\x7f\xc1\x87\xbf"
        b"\xfd\x14l\x90\xe6#\xde@\xc1\x966n[z\x85\x11\xa6\xfcc"
        b"\xdfw?s\xc4\x0b\x8e#\xbd\xc2\x08S\xe1111\xf1k\xb1NL"
        b"\xfcU<\x99\xe4T\xf8\xf43|\xaa\x18\xf8\xc3\xbaHFw\xaaj\x94"
        b"\xf4c[F\xc6\xee\xbb\xc2\xc0\x17\xf6\xf4\x12\x160\xf9"
        b"\xa3\xfeQB5\xab@\xf4\x1f\xa55r\xf9\xa4KGG\xee\x16\xdd\xff"
        b"\x8e\x9d\x8by\xc4\xe4\x17\tU\xbdDg\xf1\xeb\xf0Zh\x8e"
        b"\xd3s\x9c\xab\xc3P\n<e\xcb$\x05 b\xd8\x84Q1\x8a\xd6Kt\xe6"
        b"\x85(\x13\xe5\xf3]j\xcf\x06\x88\xe6K\x02\x84\x18\x90"
        b"\xc5\xa7Kz\xd4\x11\xeeEZK\x012\xe9\xab\xa5\xbf\xb3@i\x00"
        b"\xce\xe47\x0b\xb4\xfe\xb1d\xffk\xebh\xd3\xa3\xfd\xa4:`5J"
        b"\xa3\xf1\xf5\xf4\xcf\x02tz\x8c_\xd2\xa1\xee\xe1\xad"
        b"\xaa\xb7n-\xe5\xafoSQ\x14'\x01\xb7\x9b<\x15~\x0e\xf4b"
        b"\x8a\x90k\x8c\xdaO\xfb\x18<H\x9d\xdfj\xab\xd0\xb43\xe1"
        b'\xe3nt\x16\xdf\r\xe6\xa1d\xad\xd0\xc9z\x03"\xc7c\x94v'
        b"\xb6I\xe1\x8f\xf5,\xaa2\x93}\x90\xe0\x94\x1d\xd2\xfcY~f"
        b"\xab\r\xc1\xc8\xc4\xe4\x1f\xed\x03\x1e`\xd6\x02\xda\xc7k"
        b"\x16\x1a\xf4\xcb2Q\x05\xa0\xe6\xb4\x1e\xa4\x84\xc6"
        b"\xcc..`8'\x9a\xc9-\n\xa8\x05]?\xa3\xdfn\x11-\xcc\x0b"
        b"\xb4\x7f67:\x0c\xcf\xd5\xbb\xfd\x89\x9ebG\xf8:\x8bG"
        b"\xc0\xfb\x9dm\xe2\xdf\x80g\xea\xc4\xc45\xbe\x00\x03\xe9\xd6\xbb"
    )


@route("/upload", method="POST")
def upload():
    file = request.files.get("file")
    if not file:
        raise HTTPError(status=400, body="No file provided")

    dz_uuid = request.forms.get("dzuuid")
    if not dz_uuid:
        # Assume this file has not been chunked
        with open(storage_path / f"{uuid.uuid4()}_{secure_filename(file.filename)}", "wb") as f:
            file.save(f)
        return "File Saved"

    # Chunked download
    try:
        current_chunk = int(request.forms["dzchunkindex"])
        total_chunks = int(request.forms["dztotalchunkcount"])
    except KeyError as err:
        raise HTTPError(status=400, body=f"Not all required fields supplied, missing {err}")
    except ValueError:
        raise HTTPError(status=400, body=f"Values provided were not in expected format")

    save_dir = chunk_path / dz_uuid

    if not save_dir.exists():
        save_dir.mkdir(exist_ok=True, parents=True)

    # Save the individual chunk
    with open(save_dir / str(request.forms["dzchunkindex"]), "wb") as f:
        file.save(f)

    # See if we have all the chunks downloaded
    with lock:
        chucks[dz_uuid].append(current_chunk)
        completed = len(chucks[dz_uuid]) == total_chunks

    # Concat all the files into the final file when all are downloaded
    if completed:
        with open(storage_path / f"{dz_uuid}_{secure_filename(file.filename)}", "wb") as f:
            for file_number in range(total_chunks):
                f.write((save_dir / str(file_number)).read_bytes())
        print(f"{file.filename} has been uploaded")
        shutil.rmtree(save_dir)

    return "Chunk upload successful"


@route("/download/<dz_uuid>")
def download(dz_uuid):
    if not allow_downloads:
        raise HTTPError(status=403)
    for file in storage_path.iterdir():
        if file.is_file() and file.name.startswith(dz_uuid):
            return static_file(file.name, root=file.parent.absolute(), download=True)
    return HTTPError(status=404)


def parse_args():
    parser = argparse.ArgumentParser()
    parser.add_argument("-p", "--port", type=int, default=16273, required=False)
    parser.add_argument("--host", type=str, default="0.0.0.0", required=False)
    parser.add_argument("-s", "--storage", type=str, default=str(storage_path), required=False)
    parser.add_argument("-c", "--chunks", type=str, default=str(chunk_path), required=False)
    parser.add_argument(
        "--max-size",
        type=str,
        default=dropzone_max_file_size,
        help="Max file size (Mb)",
    )
    parser.add_argument(
        "--timeout",
        type=str,
        default=dropzone_timeout,
        help="Timeout (ms) for each chuck upload",
    )
    parser.add_argument("--chunk-size", type=str, default=dropzone_chunk_size, help="Chunk size (bytes)")
    parser.add_argument("--disable-parallel-chunks", required=False, default=False, action="store_true")
    parser.add_argument("--disable-force-chunking", required=False, default=False, action="store_true")
    parser.add_argument("-a", "--allow-downloads", required=False, default=False, action="store_true")
    parser.add_argument("--dz-cdn", type=str, default=None, required=False)
    parser.add_argument("--dz-version", type=str, default=None, required=False)
    return parser.parse_args()


if __name__ == "__main__":

    args = parse_args()
    storage_path = Path(args.storage)
    chunk_path = Path(args.chunks)
    dropzone_chunk_size = args.chunk_size
    dropzone_timeout = args.timeout
    dropzone_max_file_size = args.max_size
    try:
        if int(dropzone_timeout) < 1 or int(dropzone_chunk_size) < 1 or int(dropzone_max_file_size) < 1:
            raise Exception("Invalid dropzone option, make sure max-size, timeout, and chunk-size are all positive")
    except ValueError:
        raise Exception("Invalid dropzone option, make sure max-size, timeout, and chunk-size are all integers")

    if args.dz_cdn:
        dropzone_cdn = args.dz_cdn
    if args.dz_version:
        dropzone_version = args.dz_version
    if args.disable_parallel_chunks:
        dropzone_parallel_chunks = "false"
    if args.disable_force_chunking:
        dropzone_force_chunking = "false"
    if args.allow_downloads:
        allow_downloads = True

    if not storage_path.exists():
        storage_path.mkdir(exist_ok=True)
    if not chunk_path.exists():
        chunk_path.mkdir(exist_ok=True)

    print(
        f"""Timeout: {int(dropzone_timeout) // 1000} seconds per chunk
Chunk Size: {int(dropzone_chunk_size) // 1024} Kb
Max File Size: {int(dropzone_max_file_size)} Mb
Force Chunking: {dropzone_force_chunking}
Parallel Chunks: {dropzone_parallel_chunks}
Storage Path: {storage_path.absolute()}
Chunk Path: {chunk_path.absolute()}
"""
    )
    run(server="paste", port=args.port, host=args.host)

Make it yours, and give back if you can!

What will you add to this script? Set a max time for how long you can see the uploaded files? A way to ensure the file exists on the server before trying to download it? Checksum comparison to avoid using space for duplicate files?

However you make it better, please consider to add a pull request for your features so anyone can benefit from it!

Keep Windows from going to sleep, no power settings needed!

Say you have a long running process that you let go overnight, only to come back the next morning and realize “Oh no, only an hour into it, my computer went to sleep!”. Thanks to some Windows internals, it’s possible to make it realize there is a background task running and should not go to sleep.

Artwork by Clara Griffith

I personally use this exact method in my FastFlix program to make sure the computer doesn’t interrupt the coding process. It should work with any version of Python3, and it boils down too:

#!/usr/bin/env python
# -*- coding: UTF-8 -*-
import ctypes
import time

CONTINUOUS = 0x80000000
SYSTEM_REQUIRED = 0x00000001
DISPLAY_REQUIRED = 0x00000002 

ctypes.windll.kernel32.SetThreadExecutionState(CONTINUOUS | SYSTEM_REQUIRED)
try:
    # This is where you would do stuff
    while True:
        time.sleep(600) 
finally:
    ctypes.windll.kernel32.SetThreadExecutionState(CONTINUOUS)

As this example shows, you let this run in the background to always keep your computer from sleeping. Just be careful you don’t abuse your IT policies by allowing your computer to stay on for a lot longer than they want.

It’s pretty straightforward code, the main function being SetThreadExecutionState.

ES_CONTINUOUS 0x80000000Informs the system that the state being set should remain in effect until the next call that uses ES_CONTINUOUS and one of the other state flags is cleared.
ES_DISPLAY_REQUIRED 0x00000002Forces the display to be on by resetting the display idle timer.
ES_SYSTEM_REQUIRED 0x00000001Forces the system to be in the working state by resetting the system idle timer.
Table from https://docs.microsoft.com/en-us/windows/win32/api/winbase/nf-winbase-setthreadexecutionstate

Notice that it doesn’t take multiple arguments, like what you expect in Python. Instead it accepts a single hex value that represents the culmination of all the options you want to set. Hence why you see us passing them in via a “bitwise or” expression. For example, if you also wanted to force the screen to stay on, just need to add:

ctypes.windll.kernel32.SetThreadExecutionState(CONTINUOUS | SYSTEM_REQUIRED | DISPLAY_REQUIRED)

After this is set, it is extremely important to remember to always reset it back to ES_CONTINUOUS after your work is done.

Use atexit for safety

In our example above, we simply add this in a finally clause. For a more robust program you may want to ensure it’s always called via atexit.

#!/usr/bin/env python
# -*- coding: UTF-8 -*-
import ctypes
import atexit

CONTINUOUS = 0x80000000
SYSTEM_REQUIRED = 0x00000001
DISPLAY_REQUIRED = 0x00000002 

ctypes.windll.kernel32.SetThreadExecutionState(CONTINUOUS | SYSTEM_REQUIRED)

@atexit.register
def cleanup():
    ctypes.windll.kernel32.SetThreadExecutionState(CONTINUOUS)

# Do Stuff    

Create an image in Task Manager from CPU Usage

A lot of people have pass around a internet video of someone using a crazy high core count computer to display a video via Task Manager’s CPU usage. The one problem with it: it’s probably fake. Task Manager displays the last 60 seconds of activity, not a instant view like shown in the video. But what if we kept the usage the same for sixty seconds, could we at least make an image?

So the first problem, is how do we generate enough load for a CPU usage to noticeably increase? Luckily there is an old goto into the benchmark world that is really simple to implement. Square Roots. Throw a few million square roots at a CPU and watch it light up.

from itertools import count
import math

def run_benchmark():
    # Warning, no way to stop other than Ctrl+C or killing the process
    for num in count():
        math.sqrt(num)

run_benchmark()

The real problem is making sure we have a way to stop it. The easiest way is with a timeout, but just the slight work of gathering system time may throw off how much work we want to do in the future. So lets only do that, say, every 100,000 operations.

from itertools import count
import math
import time 

def run_benchmark(timeout=60):
    start_time = time.perf_counter()
    for num in count():
        if num % 100_000 == 0.0:
            if time.perf_counter() > start_time + timeout:
                return
        math.sqrt(num)

run_benchmark()

Excellent, now we can pump up a core to max workload. However, we currently have no control over which CPU it will run on! We have to set the “affinity” of the process. There is no easy way to do that with Python directly, and in this case we have to go straight to the Win32 API. In this case we will use the pywin32 library to access the win32process.

pip install pywin32

We will then use the SetProcessAffinityMask function to lock our program to a specific CPU, which will also require grabbing some details from GetCurrentProcess Win32 API function. One thing not really documented anywhere I could find, is the fact you set the CPU core affinity not by it’s actual number, but by the mask itself. Which we can create by taking 2 ** cpu_core.

from itertools import count
import math
import time 

import win32process  # pywin32

def run_benchmark(cpu_core=0, timeout=60):
    start_time = time.perf_counter()
    process_id = win32process.GetCurrentProcess()
    win32process.SetProcessAffinityMask(process_id, 2 ** cpu_core)

    for num in count():
        if num % 100_000 == 0.0:
            if time.perf_counter() > start_time + timeout:
                return
        math.sqrt(num)

run_benchmark()

So now every time we run the program, it should only max out the first core. If we want to do this across multiple cores, we will have to create multiple processes at the same time. My favorite way to do that is with multiprocessing maps. So instead of lighting up a single processor, let’s pump them all to the roof.

from itertools import count
import math
import time
from multiprocessing.pool import Pool
from multiprocessing import cpu_count

import win32process  # pywin32


def run_benchmark(cpu_core=0, timeout=60):
    start_time = time.perf_counter()
    process_id = win32process.GetCurrentProcess()
    win32process.SetProcessAffinityMask(process_id, 2 ** cpu_core)

    for num in count():
        if num % 100_000 == 0.0:
            if time.perf_counter() > start_time + timeout:
                return
        math.sqrt(num)


if __name__ == '__main__':
    arguments = [(core, 60) for core in range(cpu_count())]
    # [(0, 60), (1, 60), (2, 60), (3, 60)] 
    # each tuple will be as arguments to run_benchmark as its arguments

    with Pool(processes=cpu_count()) as p:
        p.starmap(run_benchmark, arguments)
    run_benchmark()

We have to throw the multiprocessing after the `if __name__ == ‘__main__’: block due to how CPython starts up on Windows. (It’s also just a good idea for any scripts.)

At this point you could also change up which cores it is running on to see how they correspond on the Task Manager. For example, you could change the range increments to only launch on each other core. range(0, cpu_count(), 2)

On my 8 core machine (so 16 logical cores) I can make a quick X shape by selecting certain cores

arguments = [(core, 100) for core in [0, 3, 5, 6, 9, 10, 12, 15]]

Now remember there are two types of CPU cores according to the operating system, physical and logical. Physical is the number of actual cores on the CPU, but if the CPU has SMT (Simultaneous multi-threading) it will double that. So that means every odd number core is actually a fake one (remember cores start at 0). Which means it has to use some of previous core’s resources. Hence why cores 2, 4, 8 and 14 are showing higher usage.

But what if we want even cooler graphics and don’t want to be limited to just 100% cpu usage? Well then we need to tell the computer to not work for very small amounts of time. Aka sleep. So lets try adding a sleep every 100K ops for oh say, 60 milliseconds.

def run_benchmark(cpu_core=0, timeout=60):
    start_time = time.perf_counter()
    process_id = win32process.GetCurrentProcess()
    win32process.SetProcessAffinityMask(process_id, 2 ** cpu_core)

    for num in count():
        if num % 100_000 == 0.0:
            if time.perf_counter() > start_time + timeout:
                return
            time.sleep(0.06)
        math.sqrt(num)

This time I am also going to run it just on physical cores.

arguments = [(core, 100, 80) for core in range(0, cpu_count(), 2)]

How about that, now it’s using just about 50% usage on each core on my computer. If you’re trying this on your own, this is where the fun begins. I suggest trying out different time offsets to see if you can get a list of times for 10~90% usage. For example, mine is close to:

usage_to_sleep_time = {
    100: 0,
    90: 0.014,
    80: 0.02,
    70: 0.03,
    60: 0.04,
    50: 0.06,
    40: 0.08,
    30: 0.1,
    20: 0.2,
    10: 0.5
}

Then lets throw that into the run_benchmark function to be able to set a precise amount of usage per core.

def run_benchmark(cpu_core=0, timeout=60, usage=100):
    start_time = time.perf_counter()
    process_id = win32process.GetCurrentProcess()
    win32process.SetProcessAffinityMask(process_id, 2 ** cpu_core)

    for num in count():
        if num % 100_000 == 0.0:
            if time.perf_counter() > start_time + timeout:
                return
            if usage != 100:
                time.sleep(usage_to_sleep_time[usage])
        math.sqrt(num)

Then if you have enough cores, you can see them all in action at the same time.

arguments = [(core, 100, usage) for core, usage in enumerate(usage_to_sleep_time)]

(I was impatient and didn’t do this one while the computer was idle, hence the messy lower ones.)

From here I am sure some of you could go crazy making individual cores ramp up and done, and create something truly spectacular, but my whistle was wetted. It is totally possible to have control over exactly how much CPU core usage is being shown in Task Manager with Python.

Here is the full final code, hope you enjoyed!

from itertools import count
import math
import time
from multiprocessing.pool import Pool
from multiprocessing import cpu_count

import win32process  # pywin32

usage_to_sleep_time = {
    100: 0,
    90: 0.014,
    80: 0.02,
    70: 0.03,
    60: 0.04,
    50: 0.06,
    40: 0.08,
    30: 0.1,
    20: 0.2,
    10: 0.5
}

def run_benchmark(cpu_core=0, timeout=60, usage=100):
    start_time = time.perf_counter()
    process_id = win32process.GetCurrentProcess()
    win32process.SetProcessAffinityMask(process_id, 2 ** cpu_core)

    for num in count():
        if num % 100_000 == 0.0:
            if time.perf_counter() > start_time + timeout:
                return num
            if usage != 100:
                time.sleep(usage_to_sleep_time[usage])
        math.sqrt(num)



if __name__ == '__main__':
    arguments = [(core, 100, usage) for core, usage in enumerate(usage_to_sleep_time)]

    with Pool(processes=len(arguments)) as p:
        print(p.starmap(run_benchmark, arguments))