The SQLite Zipfile Module
1. Overview
2. Obtaining and Compiling Zipfile
3. Using Zipfile
3.1. Table-Valued Function (read-only access)
3.2. Virtual Table Interface (read/write access)
3.2.1. Adding Entries to a Zip Archive
3.2.2. Deleting Zip Archive Entries
3.2.3. Updating Existing Zip Archive Entries
3.3. The zipfile() Aggregate Function
The zipfile module provides read/write access to simple ZIP archives.The current implementation has the following restrictions:
- Does not support encryption.
- Does not support ZIP archives that span multiple files.
- Does not support zip64 extensions.
- The only compression algorithm supported is "deflate".
Some or all of these restrictions may be removed in the future.
The code for the zipfile module is found in the ext/misc/zipfile.cfile of themain SQLite source tree.It may be compiled into an SQLite loadable extension using a command like:
gcc -g -fPIC -shared zipfile.c -o zipfile.so
Alternatively, the zipfile.c file may be compiled into the application. In this case, the following function should be invoked to register theextension with each new database connection:
int sqlite3_zipfile_init(sqlite3 *db, void*, void*);
The first argument passed should be the database handle to register theextension with. The second and third arguments should both be passed 0.
Zipfile is included in most builds of the command-line shell.
The zipfile module provides three similar interfaces for accessing, updatingand creating zip file archives:
- A table-valued function, which provides read-only access to existing archives, either from the file-system or in-memory.
- A virtual table, which provides read and write access to archives stored in the file-system.
- An SQL aggregate function, which can be used to create new archives in memory.
The zipfile module provides two similar interfaces for accessing ziparchives. A table-valued function, which provides read-only access toexisting archives, and a virtual table interface, which provides bothread and write access.
3.1. Table-Valued Function (read-only access)
For reading existing zip archives, the Zipfile module provides atable-valued function that accepts a single argument. If the argumentis a text value, then it is a path to a zip archive to read from thefile-system. Or, if the argument is an SQL blob, then it is the ziparchive data itself.
For example, to inspect the contents of zip archive "test.zip" from the current directory:
SELECT * FROM zipfile('test.zip');Or, from the SQLite shell tool (the readfile() function reads the contents of a file from the file-system and returns it as ablob):
SELECT * FROM zipfile( readfile('test.zip') );The table-valued function returns one row for each record (file, directory or symbolic link) in the zip archive. Each row has the following columns:
| ColumnName | Contents |
|---|---|
| name | File name/path for the zip file record. |
| mode | UNIX mode, as returned by stat(2) for the zip file record (an integer). This identifies the type of record (file, directory or symbolic link), and the associated user/group/all permissions. |
| mtime | UTC timestamp, in seconds since the UNIX epoch (an integer). |
| sz | Size of associated data in bytes after it has been uncompressed (an integer). |
| rawdata | Raw (possibly compressed) data associated with zip file entry (a blob). |
| data | If the compression method for the record is either 0 or 8 (see below), then the uncompressed data associated with the zip file entry. Or, if the compression method is not 0 or 8, this column contains a NULL value. |
| method | The compression method used to compress the data (an integer). The value 0 indicates that the data is stored in the zip archive without compression. 8 means the raw deflate algorithm. |
3.2. Virtual Table Interface (read/write access)
In order to create or modify an existing zip file, a "zipfile" virtual table must be created in the database schema. The CREATE VIRTUAL TABLEstatement expects a path to the zip file as its only argument. For example, towrite to zip file "test.zip" in the current directory, a zipfile table may becreated using:
CREATE VIRTUAL TABLE temp.zip USING zipfile('test.zip');Such a virtual table has the same columns as the table-valued functiondescribed in the previous section. It may be read from using a SELECT statement in the same way as the table-valued function can.
Using the virtual table interface, new entries may be added to a ziparchive by inserting new rows into the virtual table. Entries may beremoved by deleting rows or modified by updating them.
3.2.1. Adding Entries to a Zip Archive
Entries may be added to a zip archive by inserting new rows. The easiestway to do this is to specify values for the "name" and "data" columns only andhave zipfile fill in sensible defaults for other fields. To insert a directoryinto the archive, set the "data" column to NULL. For example, to add thedirectory "dir1" and the file "m.txt" containing the text "abcdefghi" to ziparchive "test.zip":
INSERT INTO temp.zip(name, data) VALUES('dir1', NULL); -- Add directory INSERT INTO temp.zip(name, data) VALUES('m.txt', 'abcdefghi'); -- Add regular file When a directory is inserted, if the "name" value does not end witha '/' character, the zipfile module appends one. This is necessary forcompatibility with other programs (most notably "info-zip") that manipulate zip archives.
To insert a symbolic link, the user must also supply a "mode" value.For example, to add a symbolic link from "link.txt" to "m.txt":
INSERT INTO temp.zip(name, mode, data) VALUES('link.txt', 'lrwxrw-rw-', 'abcdefghi');The following rules and caveats apply to the values specified as part ofeach INSERT statement:
| Columns | Notes |
|---|---|
| name | A non-NULL text value must be specified for the name column. It is an error if the specified name already exists in the archive. |
| mode | If NULL is inserted into the mode column, then the mode of the new archive entry is automatically set to either 33188 (-rw-r--r--) or 16877 (drwxr-xr-x), depending on whether or not the values specified for columns "sz", "data" and "rawdata" indicate that the new entry is a directory. If the specified value is an integer (or text that looks like an integer), it is inserted verbatim. If the value is not a valid UNIX mode, some programs may behave unexpectedly when extracting files from the archive. Finally, if the value specified for this column is not an integer or a NULL, then it is assumed to be a UNIX permissions string similar to those output by the "ls -l" command (e.g. "-rw-r--r--", "drwxr-xr-x" etc.). In this case, if the string cannot be parsed it is an error. |
| mtime | If NULL is inserted into the mtime column, then the timestamp of the new entry is set to the current time. Otherwise, the specified value is interpreted as an integer and used as is. |
| sz | This column must be set to NULL. If a non-NULL value is inserted into this column, or if a new non-NULL value is provided using an UPDATE statement, it is an error. |
| rawdata | This column must be set to NULL. If a non-NULL value is inserted into this column, or if a new non-NULL value is provided using an UPDATE statement, it is an error. |
| data | To insert a directory into the archive, this field must be set to NULL. In this case if a value was explicitly specified for the "mode" column, then it must be consistent with a directory (i.e. it must be true that (mode & 0040000)=0040000). Otherwise, the value inserted into this field is the file contents for a regular file, or the target of a symbolic link. |
| method | This field must be set one of integer values 0 and 8, or else to NULL. For a directory entry, any value inserted into this field is ignored. Otherwise, if it is set to 0, then the file data or symbolic link target is stored as is in the zip archive and the compression method set to 0. If it is set to 8, then the file data or link target is compressed using deflate compression before it is stored and the compression method set to 8. Finally, if a NULL value is written to this field, the zipfile module automatically decides whether or not to compress the data before storing it. |
Specifying an explicit value for the rowid field as part of an INSERTstatement is not supported. Any value supplied is ignored.
3.2.2. Deleting Zip Archive Entries
Records may be removed from an existing zip archive by deleting thecorresponding rows. For example, to remove file "m.txt" from zip archive"test.zip" using the virtual table created above:
DELETE FROM temp.zip WHERE name = 'm.txt';
Note that deleting records from a zip archive does not reclaim the space used within the archive - it merely removes an entry from thearchives "Central Directory Structure", making the entry inaccessible.One way to work around this inefficiency is to create a new zip archive based on the contents of the edited archive. For example, afterediting the archive accessed via virtual table temp.zzz:
-- Create a new, empty, archive: CREATE VIRTUAL TABLE temp.newzip USING zipfile('new.zip');-- Copy the contents of the existing archive into the new archiveINSERT INTO temp.newzip(name, mode, mtime, data, method) SELECT name, mode, mtime, data, method FROM temp.zzz;3.2.3. Updating Existing Zip Archive Entries
Existing zip archive entries may be modified using UPDATE statements.
The three leftmost columns of a zipfile virtual table, "name", "mode" and "mtime", may each be set to any value that may be inserted into the samecolumn (see above). If either "mode" or "mtime" is set to NULL, the final value is determined as described for an INSERT of a NULL value - the currenttime for "mtime" and either 33188 or 16877 for "mode", depending on whether or not the values specified for the next four columns of the zipfile tableindicate that the entry is a directory or a file.
It is an error to attempt to set the sz or rawdata field to any valueother than NULL.
The data and method columns may also be set as described for an INSERTabove.
3.3. The zipfile() Aggregate Function
New zip archives may be constructed entirely within memory using thezipfile() aggregate function. Each row visited by the aggregate functionadds an entry to the zip archive. The value returned is a blob containingthe entire archive image.
The zipfile() aggregate function may be called with 2, 4 or 5 arguments. If it is called with 5 arguments, then the entry added tothe archive is equivalent to inserting the same values into the "name", "mode", "mtime", "data" and "method" columns of a zipfile virtual table.
If zipfile() is invoked with 2 arguments, then the entry added tothe archive is equivalent to that added by inserting the same two values intothe "name" and "data" columns of a zipfile virtual table, with allother values set to NULL. If invoked with 4 arguments, it is equivalentto inserting the 4 values into the "name", "mode", "mtime" and "data"columns. In other words, the following pairs of queries are equivalent:
SELECT zipfile(name, data) ...SELECT zipfile(name, NULL, NULL, data, NULL) ...SELECT zipfile(name, mode, mtime, data) ...SELECT zipfile(name, mode, mtime, data, NULL) ...
For example, to create an archive containing two text files, "a.txt" and"b.txt", containing the text "abc" and "123" respectively:
WITH contents(name, data) AS ( VALUES('a.txt', 'abc') UNION ALL VALUES('b.txt', '123'))SELECT zipfile(name, data) FROM contents;This page last modified on 2018-03-10 12:09:19 UTC
FAQs
What is ZIP file in Python? ›
Python's zipfile is a standard library module intended to manipulate ZIP files. This file format is a widely adopted industry standard when it comes to archiving and compressing digital data. You can use it to package together several related files.
How to import sqlite3 module in Python? ›- import sqlite3 # Create a SQL connection to our SQLite database con = sqlite3. ...
- import sqlite3 # Create a SQL connection to our SQLite database con = sqlite3. ...
- import pandas as pd import sqlite3 # Read sqlite query results into a pandas DataFrame con = sqlite3.
First, go to SQLite's official website download page and download precompiled binaries from Windows section. Once the download is completed, you should see the downloaded file in the Windows Downloads directory. Next, right click on the downloaded file and extract it inside the C:\sqlite directory.
How do I create a ZIP file in Python? ›- import shutil import os. ...
- import os from zipfile import ZipFile # Create a ZipFile Object with ZipFile('E:/Zipped file.zip', 'w') as zip_object: # Adding files that need to be zipped zip_object.
ZipFile Objects. Open a ZIP file, where file can be a path to a file (a string), a file-like object or a path-like object. The mode parameter should be 'r' to read an existing file, 'w' to truncate and write a new file, 'a' to append to an existing file, or 'x' to exclusively create and write a new file.
What is the purpose of a ZIP file? ›Zipped (compressed) files take up less storage space and can be transferred to other computers more quickly than uncompressed files. In Windows, you work with zipped files and folders in the same way that you work with uncompressed files and folders.
How to install sqlite3 in Python? ›Installation. SQLite3 can be integrated with Python using sqlite3 module, which was written by Gerhard Haring. It provides an SQL interface compliant with the DB-API 2.0 specification described by PEP 249. You do not need to install this module separately because it is shipped by default along with Python version 2.5.
Do I need to install sqlite3 Python? ›SQLite is a self-contained, file-based SQL database. SQLite comes bundled with Python and can be used in any of your Python applications without having to install any additional software.
What is Python sqlite3 module? ›Source code: Lib/sqlite3/ SQLite is a C library that provides a lightweight disk-based database that doesn't require a separate server process and allows accessing the database using a nonstandard variant of the SQL query language. Some applications can use SQLite for internal data storage.
Is SQLite preinstalled on Windows? ›SQLite provides various tools for working across platforms e.g., Windows, Linux, and Mac. You need to select an appropriate version to download. For example, to work with SQLite on Windows, you download the command-line shell program as shown in the screenshot below.
Does SQLite need to be installed? ›
SQLite does not need to be "installed" before it is used. There is no "setup" procedure. There is no server process that needs to be started, stopped, or configured. There is no need for an administrator to create a new database instance or assign access permissions to users.
Is SQLite included in Windows? ›All supported versions of Windows support SQLite, so your app does not have to package SQLite libraries.
How do you create a zip file step by step? ›Right-click on the file or folder.
Select “Compressed (zipped) folder”. To place multiple files into a zip folder, select all of the files while hitting the Ctrl button. Then, right-click on one of the files, move your cursor over the “Send to” option and select “Compressed (zipped) folder”.
- To select sql file(s), you have two options: ...
- (Optional) Set the desired compression level by clicking the down arrow next to "Convert to ZIP".
- Click "Convert to ZIP" to initiate the conversion.
It is itertools. izip() : Make an iterator that aggregates elements from each of the iterables. Like zip() except that it returns an iterator instead of a list.
How do I read a ZipFile in Python? ›...
Steps To Solve The Problem
- Open the zip with the name variable.
- Get the password of the Zip from the name variable.
- Extract the Zip.
- Get and store the next Zip name in the name variable.
To unzip it first create a ZipFile object by opening the zip file in read mode and then call extractall() on that object. It will extract all the files in the current directory. If the file path argument is provided, then it will overwrite the path.
How do I use Python file modules? ›A file is considered as a module in python. To use the module, you have to import it using the import keyword. The function or variables present inside the file can be used in another file by importing the module. This functionality is available in other languages, like typescript, JavaScript, java, ruby, etc.
Should I trust Zip files? ›Zip files by themselves are not harmful or dangerous. However, they have been used by malicious individuals to hide the fact that they are sending harmful files.
Are zip file safe? ›Are Zip files dangerous? Zip files are not dangerous. However, it is essential to take caution when opening files you have imported from unknown sources or the files you have downloaded from the internet. Some may contain a virus, zip bombs, Trojans, or other malware.
When I zip a file where does it go? ›
If you downloaded the ZIP file from the internet or as an email attachment, you might find it in the Downloads folder in your System Drive.
How do I open a sqlite3 database in Python? ›- Import sqlite3 module. ...
- Use the connect() method. ...
- Use the cursor() method. ...
- Use the execute() method. ...
- Extract result using fetchall() ...
- Close cursor and connection objects. ...
- Catch database exception if any that may occur during this connection process.
- Step 1: Create the Database and Tables. In this step, you'll see how to create: ...
- Step 2: Insert values into the tables. For this step, let's insert the following data into the 'products' table: ...
- Step 3: Display the results.
Method 1: pip show. To check which version of the Python library sqlite3 is installed, run pip show sqlite3 or pip3 show sqlite3 in your CMD/Powershell (Windows), or terminal (macOS/Linux/Ubuntu).
For what purpose sqlite3 is used for? ›A standalone command-line shell program called sqlite3 is provided in SQLite's distribution. It can be used to create a database, define tables, insert and change rows, run queries and manage an SQLite database file. It also serves as an example for writing applications that use the SQLite library.
Why should I use SQLite? ›SQLite is used to develop embedded software for devices like televisions, cell phones, cameras, etc. It can manage low to medium-traffic HTTP requests. SQLite can change files into smaller size archives with lesser metadata. SQLite is used as a temporary dataset to get processed with some data within an application.
Is it good to use SQLite? ›SQLite works great as the database engine for most low to medium traffic websites (which is to say, most websites). The amount of web traffic that SQLite can handle depends on how heavily the website uses its database. Generally speaking, any site that gets fewer than 100K hits/day should work fine with SQLite.
How do I run SQLite in Python? ›- First, establish a connection to the SQLite database by creating a Connection object.
- Next, create a Cursor object using the cursor method of the Connection object.
- Then, execute a SELECT statement.
- After that, call the fetchall() method of the cursor object to fetch the data.
SQLite vs SQL (Comparison) The main difference between them is that SQL stands for Structured Query Language, which is the query language used with databases. But SQLite is a portable database. Extensions can be added to the computer language used to access the database.
How to install SQLite3 in Python in Windows? ›- Step 1 − Go to SQLite download page, and download precompiled binaries from Windows section.
- Step 2 − Download sqlite-shell-win32-*. ...
- Step 3 − Create a folder C:\>sqlite and unzip above two zipped files in this folder, which will give you sqlite3.
What devices use SQLite? ›
- Every Android device.
- Every iPhone and iOS device.
- Every Mac.
- Every Windows10 machine.
- Every Firefox, Chrome, and Safari web browser.
- Every instance of Skype.
- Every instance of iTunes.
- Every Dropbox client.
Adobe uses SQLite as the application file format for their Photoshop Lightroom product. SQLite is also a standard part of the Adobe Integrated Runtime (AIR). It is reported that Acrobat Reader also uses SQLite. Airbus confirms that SQLite is being used in the flight software for the A350 XWB family of aircraft.
How do I know if SQLite is installed Windows 10? ›Check for SQLite
The first thing to do is to check whether SQLite is installed on your system or not. You can do this simply by entering sqlite3 into your system's command line interface (assuming version 3+ is installed).
SQLite is an open-source relational database i.e. used to perform database operations on android devices such as storing, manipulating or retrieving persistent data from the database. It is embedded in android bydefault. So, there is no need to perform any database setup or administration task.
How do I view a SQLite database? ›Open a command prompt (cmd.exe) and 'cd' to the folder location of the SQL_SAFI. sqlite database file. run the command 'sqlite3' This should open the SQLite shell and present a screen similar to that below.
Why does Android use SQLite? ›SQLite Database is an open-source database provided in Android which is used to store data inside the user's device in the form of a Text file. We can perform so many operations on this data such as adding new data, updating, reading, and deleting this data.
Where is my SQLite database file? ›There is no "standard place" for a sqlite database. The file's location is specified to the library, and may be in your home directory, in the invoking program's folder, or any other place. If it helps, sqlite databases are, by convention, named with a . db file extension.
Where is SQLite stored in Windows? ›The SQLite files are generally stored on the internal storage under /data/data/<packageName>/databases. However, there are no restrictions on creating databases elsewhere. SQLite databases are a rich source of forensic data.
Is SQLite a real database? ›SQLite is an open-source database maintained by a group of developers. For community support, it offers a public mailing list and also offers paid professional support. Some of the key customers of SQLite are Facebook, Google, and Apple.
What program do I need to open a ZIP file? ›ZIP Extractor is a free app for creating and opening ZIP files on your computer and Google Drive. Files in the RAR, 7z, and TAR format are also supported, including password-protected files. ZIP Extractor is a free app for creating and opening ZIP files on your computer and Google Drive.
What program creates zip files? ›
#1) WinRAR
WinRAR is a zip software that allows you to create ZIP and RAR archives. This software allows you to add text comments to archives. The tool is available in more than 50 languages. It automatically recognizes and selects the ideal compression method.
- Open File Explorer and find the zipped folder.
- To unzip the entire folder, right-click to select Extract All, and then follow the instructions.
- To unzip a single file or folder, double-click the zipped folder to open it. Then, drag or copy the item from the zipped folder to a new location.
We cannot import data from a ZIP file directly into SQL Server. We need to extract the file first and then import the excel file into SQL Server and extract the files into a different folder using the SSIS package only. We have the following ZIP file into our source path.
What is SQL zip? ›sql. zip is not a file type, it's just a naming convention. .zip is the file type.
Can you zip a SQL database? ›SQL Backup Master allows you to optionally compress and/or encrypt your database backups before sending them to one or more backup destinations. Compression method - Choose between Disable (the archive file is created), Zip, and 7-Zip (LZMA) compression methods.
Why is zip used in Python? ›zip() in Python
Python zip() method takes iterable or containers and returns a single iterator object, having mapped values from all the containers. It is used to map the similar index of multiple containers so that they can be used just using a single entity.
Zip is an in-built function in Python used to iterate over multiple iterables. It takes corresponding elements from all the iterable passed to it and merges them in a tuple. Note: Tuples are immutable data structures defined with parenthesis that store an ordered sequence of values.
Is zip efficient in Python? ›There are circumstances where iterative for-looping might not be able to get a job done very effectively. That being said, for the circumstance of iterating multiple elements at once, typical iteration of lists can be problematic. Fortunately, Python comes with a great solution for this problem called zip.
What is zipping and unzipping in Python? ›Zipping and unzipping a file
In Python, the module zipfile contains ZipFile class that helps us to zip or unzip a file contents. For example, to zip the files, we should first pass the zip file name in write mode with an attribute ZIP_DEFLATED to the ZipFile class object as: f = ZipFile('test.zip', 'w', ZIP_DEFLATED)
- import requests, zipfile, StringIO.
- r = requests.get('http://data.octo.dc.gov/feeds/crime_incidents/archive/crime_incidents_2013_CSV.zip')
- z = zipfile.ZipFile(StringIO.StringIO(r.content))
- crime2013 = pandas.read_csv(z.read('crime_incidents_2013_CSV.csv'))
How does zip and unzip work in Python? ›
The unpacking operator * will unpack the first_and_last_names list of tuples into its tuples. These tuples will then be passed to the zip() function, which will take these separate iterable objects (the tuples), and combines their same-indexed elements together into tuples, making two separate tuples.
How do I create a .zip file? ›Right-click on the file or folder.
Select “Compressed (zipped) folder”. To place multiple files into a zip folder, select all of the files while hitting the Ctrl button. Then, right-click on one of the files, move your cursor over the “Send to” option and select “Compressed (zipped) folder”.
Python can work directly with data in ZIP files. You can look at the list of items in the directory and work with the data files themselves. This recipe is a snippet that lists all of the names and content lengths of the files included in the ZIP archive zipfile. zip .
How to install zipfile Python? ›- Download the pynrfjprog zip file.
- Extract the compressed zip file and open a Command Prompt window within that directory.
- Type python setup.py install at the Command Prompt. The content of the package will be added to the Python defaults directory.
If you want to import modules and packages from a ZIP file, then you just need the file to appear in Python's module search path. The module search path is a list of directories and ZIP files. It lives in sys. path .
How do I read ZIP files? ›- On your Android device, open Files by Google .
- On the bottom, tap Browse .
- Navigate to the folder that contains a . zip file you want to unzip.
- Select the . zip file.
- A pop up appears showing the content of that file.
- Tap Extract.
- You're shown a preview of the extracted files. ...
- Tap Done.
When you extract files from a zipped folder, a new folder with the same name is created which contains the files. The compressed (zipped) version also remains. Right-click the zipped folder saved to your computer.
What program creates Zip files? ›#1) WinRAR
WinRAR is a zip software that allows you to create ZIP and RAR archives. This software allows you to add text comments to archives. The tool is available in more than 50 languages. It automatically recognizes and selects the ideal compression method.
ZIP Extractor is a free app for creating and opening ZIP files on your computer and Google Drive. Files in the RAR, 7z, and TAR format are also supported, including password-protected files. ZIP Extractor is a free app for creating and opening ZIP files on your computer and Google Drive.
What is a zip folder? ›Compressed (zipped) Folders overview. Folders that are compressed using the Compressed (zipped) Folders feature use less drive space and can be transferred to other computers more quickly. You can work with a compressed folder and the files or programs it contains just as you would an uncompressed folder.