Flametree | : fire : Python file and zip operations | Compression library
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kandi X-RAY | Flametree Summary
:fire: Python file and zip operations made easy
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- Use setuptools
- Extract all members of the tar
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- Return a file - like object
- Read the contents of a file
- Returns the relative path to this target
- Create directory if it does not exist
- Check if a directory exists in the file
- List files in a given directory
- List the content of a directory
- Create the target directory
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- Read file contents
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Community Discussions
Trending Discussions on Compression
QUESTION
Let me explain: in my use case a system gives me many strings that can vary in size (number of characters; length), sometimes it can be really huge! The problem is that I have to save this string in a column of a table of a "SQL Server" database, the bad news is that I am not allowed to do any migration in this database, the good news is that the column already has type nvarchar(max).
I've done some research before and followed the following post to write a data compressor using "Gzip" and "Brotli".
https://khalidabuhakmeh.com/compress-strings-with-dotnet-and-csharp
...ANSWER
Answered 2022-Apr-15 at 13:55The max size for a column of type NVARCHAR(MAX) is 2 GByte of storage.
Since NVARCHAR uses 2 bytes per character, that's approx. 1 billion characters.
So I don't think you actually need to make a compression, if the problem is the performance when retrieving data, then you can use a server side caching system.
QUESTION
Good Day!
I would like ask for your help on decompressing String back to its original data.
Here's the document that was sent to me by the provider.
Data description
First part describes the threshold data.
All data are managed as Little Endian IEEE 754 single precision floating numbers. Their binary representation are (represented in hexadecimal data) :
Compressed data (zip) Threshold binary data are compressed using the ‘deflate’ algorithm. Each compression result is given here (represented in hexadecimal data) :
Thresholds: $63 00 03 05 47 24 DA 81 81 A1 C1 9E 81 61 01 98 06 00
Encoded data (base64) Threshold compressed data are encoded in ‘base64’ to be transmitted as ASCII characters. Each conversion results is given here (represented in hexadecimal data) :
Thresholds: $59 77 41 44 42 55 63 6B 32 6F 47 42 6F 63 47 65 67 57 45 42 6D 41 59 41
Here is the output frame (Manufacturer frame content) The thresholds data are then sent using their corresponding ASCII character Here is the resulting Histogram ASTM frame sent :
YwADBUck2oGBocGegWEBmAYA
As explained in above details, what I want to do is backwards.
The packets that we received is
YwADBUck2oGBocGegWEBmAYA
then from there convert it to Hex value Base64 which is the output is.
Thresholds: $59 77 41 44 42 55 63 6B 32 6F 47 42 6F 63 47 65 67 57 45 42 6D 41 59 41
This first part was already been implemented using this line of codes.
...ANSWER
Answered 2022-Mar-23 at 16:03Your input string is a base64 encoded array of bytes, representing a compressed (deflated) sequence of floating point values (float / Single).
- You can use Convert.FromBase64String() to get the compressed bytes
- Initialize a MemoryStream with this byte array. It's used as the input stream of a DeflateStream
- Initialize a new MemoryStream to receive the deflated content from the DeflateStream.CopyTo() method
- Get a series of 4 bytes from the decompressed array of bytes and reconstruct the original values (here, using BitConverter.ToSingle() and an ArraySegment(Of Byte)).
An example:
QUESTION
Is there a way during the ffmpeg compression process to determine over various intervals the exact filesize that a video is at?
Such as a method to get current filesize during the process to use when comparing against the videos original filesize.
For example, a potential video being transcoded takes 5 minutes, but during the process, a function will check the file size on intervals of 100 frames or every 5 seconds to ensure that the filesize hasn't exceeded the original. If it has, it will kill the process with command.kill('SIGSTOP');
ANSWER
Answered 2022-Mar-22 at 01:56You can use the targetSize property from the "progress" event to get the current size of the target file:
QUESTION
Is the Shannon-Fano coding as described in Fano's paper The Transmission of Information (1952) really ambiguous?
In Detail:3 papers
Claude E. Shannon published his famous paper A Mathematical Theory of Communication in July 1948. In this paper he invented the term bit as we know it today and he also defined what we call Shannon entropy today. And he also proposed an entropy based data compression algorithm in this paper. But Shannon's algorithm was so weak, that under certain circumstances the "compressed" messages could be even longer than in fix length coding. A few month later (March 1949) Robert M. Fano published an improved version of Shannons algorithm in the paper The Transmission of Information. 3 years after Fano (in September 1952) his student David A. Huffman published an even better version in his paper A Method for the Construction of Minimum-Redundancy Codes. Hoffman Coding is more efficient than its two predecessors and it is still used today. But my question is about the algorithm published by Fano which usually is called Shannon-Fano-Coding.
The algorithm
This description is based on the description from Wikipedia. Sorry, I did not fully read Fano's paper. I only browsed through it. It is 37 pages long and I really tried hard to find a passage where he talks about the topic of my question, but I could not find it. So, here is how Shannon-Fano encoding works:
- Count how often each character appears in the message.
- Sort all characters by frequency, characters with highest frequency on top of the list
- Divide the list into two parts, such that the sums of frequencies in both parts are as equal as possible. Add the bit
0to one part and the bit1to the other part. - Repeat step 3 on each part that contains 2 or more characters until all parts consist of only 1 character.
- Concatenate all bits from all rounds. This is the Shannon-Fano-code of that character.
An example
Let's execute this on a really tiny example (I think it's the smallest message where the problem appears). Here is the message to encode:
ANSWER
Answered 2022-Mar-08 at 19:00To directly answer your question, without further elaboration about how to break ties, two different implementations of Shannon-Fano could produce different codes of different lengths for the same inputs.
As @MattTimmermans noted in the comments, Shannon-Fano does not always produce optimal prefix-free codings the way that, say, Huffman coding does. It might therefore be helpful to think of it less as an algorithm and more of a heuristic - something that likely will produce a good code but isn't guaranteed to give an optimal solution. Many heuristics suffer from similar issues, where minor tweaks in the input or how ties are broken could result in different results. A good example of this is the greedy coloring algorithm for finding vertex colorings of graphs. The linked Wikipedia article includes an example in which changing the order in which nodes are visited by the same basic algorithm yields wildly different results.
Even algorithms that produce optimal results, however, can sometimes produce different optimal results based on tiebreaks. Take Huffman coding, for example, which works by repeatedly finding the two lowest-weight trees assembled so far and merging them together. In the event that there are three or more trees at some intermediary step that are all tied for the same weight, different implementations of Huffman coding could produce different prefix-free codes based on which two they join together. The resulting trees would all be equally "good," though, in that they'd all produce outputs of the same length. (That's largely because, unlike Shannon-Fano, Huffman coding is guaranteed to produce an optimal encoding.)
That being said, it's easy to adjust Shannon-Fano so that it always produces a consistent result. For example, you could say "in the event of a tie, choose the partition that puts fewer items into the top group," at which point you would always consistently produce the same coding. It wouldn't necessarily be an optimal encoding, but, then again, since Shannon-Fano was never guaranteed to do so, this is probably not a major concern.
If, on the other hand, you're interested in the question of "when Shannon-Fano has to break a tie, how do I decide how to break the tie to produce the optimal solution?," then I'm not sure of a way to do this other than recursively trying both options and seeing which one is better, which in the worst case leads to exponentially-slow runtimes. But perhaps someone else here can find a way to do that>
QUESTION
Final Update: Turns out I didn't need Binary writer. I could just copy memory streams from one archive to another.
I'm re-writing a PowerShell script which works with archives. I'm using two functions from here
Expand-Archive without Importing and Exporting files
and can successfully read and write files to the archive. I've posted the whole program just in case it makes things clearer for someone to help me.
However, there are three issues (besides the fact that I don't really know what I'm doing).
1.) Most files have this error on when trying to run
Add-ZipEntry -ZipFilePath ($OriginalArchivePath + $PartFileDirectoryName) -EntryPath $entry.FullName -Content $fileBytes}
Cannot convert value "507" to type "System.Byte". Error: "Value was either too large or too small for an unsigned byte." (replace 507 with whatever number from the byte array is there)
2.) When it reads a file and adds it to the zip archive (*.imscc) it adds a character "a" to the beginning of the file contents.
3.) The only file it doesn't error on are text files, when I really want it to handle any file
Thank you for any assistance!
Update: I've tried using System.IO.BinaryWriter, with the same errors.
...ANSWER
Answered 2022-Feb-27 at 13:55System.IO.StreamWriter is a text writer, and therefore not suitable for writing raw bytes. Cannot convert value "507" to type "System.Byte" indicates that an inappropriate attempt was made to convert text - a .NET string composed of [char] instances which are in effect [uint16] code points (range 0x0 - 0xffff) - to [byte] instances (0x0 - 0xff). Therefore, any Unicode character whose code point is greater than 255 (0xff) will cause this error.
The solution is to use a .NET API that allows writing raw bytes, namely System.IO.BinaryWriter:
QUESTION
I have been trying to make a python script to zip a file with the zipfile module. Although the text file is made into a zip file, It doesn't seem to be compressing it; testtext.txt is 1024KB whilst testtext.zip (The code's creation) is also equal to 1024KB. However, if I compress testtext.txt manually in File Explorer, the resulting zip file is compressed (To 2KB, specifically). How, if possible, can I combat this logical error?
Below is the script that I have used to (unsuccessfully) zip a text file.
...ANSWER
Answered 2022-Feb-26 at 16:09In the docs they have it written with a with statement so I would try that first.
Edit:
I just came back to say that you have to specify your compression method but Mark beat me to the punch.
Here is a link to a StackOverflow post about it https://stackoverflow.com/questions/4166447/python-zipfile-module-doesnt-seem-to-be-compressing-my-files#:~:text=This%20is%20because%20ZipFile%20requires,the%20method%20to%20be%20zipfile.
QUESTION
I am learning F# and Deedle. I am trying to extract the contents of this TGZ File using SharpZipLib. I downloaded the TGZ to my local drive. I think I am close because out1 works, but out2 errs. I am sure the code could be written better with pipe forwarding or composition, but it first needs to work. Does anyone have any ideas?
...ANSWER
Answered 2022-Feb-22 at 01:44Does this help?
https://stackoverflow.com/a/52200001/1594263
Looks like you should be using CreateInputTarArchive(). I modified your example to use CreateInputTarArchive(), and it worked for me.
BTW you're just assigning a function to out1, you're not actually calling ListContents().
QUESTION
I've been working on a little side project of listing files compressed in nested zip files. I've cooked up a script that does just that, but only if the depth of zip files is known. In in example below the zip file has additional zips in it and then anthoer in one of them.
...ANSWER
Answered 2022-Feb-17 at 18:26Here you have a little example of how recursion would look like, basically, you loop over the .Entries property of ZipFile and check if the extension of each item is .zip, if it is, then you pass that entry to your function.
EDIT: Un-deleting this answer mainly to show how this could be approached using a recursive function, my previous answer was inaccurate. I was using [ZipFile]::OpenRead(..) to read the nested .zip files which seemed to work correctly on Linux (.NET Core) however it clearly does not work when using Windows PowerShell. The correct approach would be to use [ZipArchive]::new($nestedZip.Open()) as Sage Pourpre's helpful answer shows.
QUESTION
I would like to include -co options to compress output raster using gdalwarp from gdalUtilities in R.
I have tried some options (commented in the code), but I have not been successful in generating the compressed raster.
...ANSWER
Answered 2022-Feb-09 at 21:101 - COMPRESSION
Please find the solution for the problem of file compression. To be honest, I have already been confronted with the same problem as you and, at the time, I was racking my brains... to finally find the solution which is quite simple (once we know it!): you must not put any spaces (i.e. "COMPRESS=DEFLATE" and not "COMPRESS = DEFLATE")
So, please find below a small reprex.
Reprex
QUESTION
I have managed to convert zip files to gzip, using AWS lambda's local storage /tmp. The problem is that this storage maxes out at 500Mb.
ANSWER
Answered 2022-Feb-07 at 18:06This should do as you ask:
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