Jing Zhang

Jing Zhang

1582572720

How to integrate MongoDB with Python using PyMongo

Introduction

In this post, we will dive into MongoDB as a data store from a Python perspective. To that end, we’ll write a simple script to showcase what we can achieve and any benefits we can reap from it.

Web applications, like many other software applications, are powered by data. The organization and storage of this data are important as they dictate how we interact with the various applications at our disposal. The kind of data handled can also have an influence on how we undertake this process.

Databases allow us to organize and store this data, while also controlling how we store, access, and secure the information.

NoSQL Databases

There are two main types of databases - relational and non-relational databases.

Relational databases allow us to store, access, and manipulate data in relation to another piece of data in the database. Data is stored in organized tables with rows and columns with relationships linking the information among tables. To work with these databases, we use the Structured Query Language (SQL) and examples include MySQL and PostgreSQL.

Non-relational databases store data in neither relation or tabular, as in relational databases. They are also referred to as NoSQL databases since we do not use SQL to interact with them.

Furthermore, NoSQL databases can be divided into Key-Value stores, Graph stores, Column stores, and Document Stores, which MongoDB falls under.

MongoDB and When to Use it

MongoDB is a document store and non-relational database. It allows us to store data in collections that are made up of documents.

In MongoDB, a document is simply a JSON-like binary serialization format referred to as a BSON, or Binary-JSON, and has a maximum size of 16 megabytes. This size limit is in place to ensure efficient memory and bandwidth usage during transmission.

MongoDB also provides the GridFS specification in case there is a need to store files larger than the set limit.

Documents are made up of field-value pairs, just like in regular JSON data. However, this BSON format can also contain more data types, such as Date types and Binary Data types. BSON was designed to be lightweight, easily traversable, and efficient when encoding and decoding data to and from BSON.

Being a NoSQL datastore, MongoDB allows us to enjoy the advantages that come with using a non-relational database over a relational one. One advantage is that it offers high scalability by efficiently scaling horizontally through sharding or partitioning of the data and placing it on multiple machines.

MongoDB also allows us to store large volumes of structured, semi-structured, and unstructured data without having to maintain relationships between it. Being open-source, the cost of implementing MongoDB is kept low to just maintenance and expertise.

Like any other solution, there are downsides to using MongoDB. The first one is that it does not maintain relationships between stored data. Due to this, it is hard to perform ACID transactions that ensure consistency.

Complexity is increased when trying to support ACID transactions. MongoDB, like other NoSQL data stores, is not as mature as relational databases and this can make it hard to find experts.

The non-relational nature of MongoDB makes it ideal for the storage of data in specific situations over its relational counterparts. For instance, a scenario where MongoDB is more suitable than a relational database is when the data format is flexible and has no relations.

With flexible/non-relational data, we don’t need to maintain ACID properties when storing data as opposed to relational databases. MongoDB also allows us to easily scale data into new nodes.

However, with all its advantages, MongoDB is not ideal when our data is relational in nature. For instance, if we are storing customer records and their orders.

In this situation, we will need a relational database to maintain the relationships between our data, which are important. It is also not suitable to use MongoDB if we need to comply with ACID properties.

Interacting with MongoDB via Mongo Shell

To work with MongoDB, we will need to install the MongoDB Server, which we can download from the official homepage. For this demonstration, we will use the free Community Server.

The MongoDB server comes with a Mongo Shell that we can use to interact with the server via the terminal.

To activate the shell, just type mongo in your terminal. You’ll be greeted with information about the MongoDB server set-up, including the MongoDB and Mongo Shell version, alongside the server URL.

For instance, our server is running on:

mongodb://127.0.0.1:27017

In MongoDB, a database is used to hold collections that contains documents. Through the Mongo shell, we can create a new database or switch to an existing one using the use command:

> use SeriesDB

Every operation we execute after this will be effected in our SeriesDB database. In the database, we will store collections, which are similar to tables in relational databases.

For example, for the purposes of this tutorial, let’s add a few series to the database:

> db.series.insertMany([
... { name: "Game of Thrones", year: 2012},
... { name: "House of Cards", year: 2013 },
... { name: "Suits", year: 2011}
... ])

We’re greeted with:

{
    "acknowledged" : true,
    "insertedIds" : [
        ObjectId("5e300724c013a3b1a742c3b9"),
        ObjectId("5e300724c013a3b1a742c3ba"),
        ObjectId("5e300724c013a3b1a742c3bb")
    ]
}

To fetch all the documents stored in our series collection, we use db.inventory.find({}), whose SQL equivalent is SELECT * FROM series. Passing an empty query (i.e. {}) will return all the documents:

> db.series.find({})

{ "_id" : ObjectId("5e3006258c33209a674d1d1e"), "name" : "The Blacklist", "year" : 2013 }
{ "_id" : ObjectId("5e300724c013a3b1a742c3b9"), "name" : "Game of Thrones", "year" : 2012 }
{ "_id" : ObjectId("5e300724c013a3b1a742c3ba"), "name" : "House of Cards", "year" : 2013 }
{ "_id" : ObjectId("5e300724c013a3b1a742c3bb"), "name" : "Suits", "year" : 2011 }

We can also query data using the equality condition, for instance, to return all the TV series that premiered in 2013:

> db.series.find({ year: 2013 })
{ "_id" : ObjectId("5e3006258c33209a674d1d1e"), "name" : "The Blacklist", "year" : 2013 }
{ "_id" : ObjectId("5e300724c013a3b1a742c3ba"), "name" : "House of Cards", "year" : 2013 }

The SQL equivalent would be SELECT * FROM series WHERE year=2013.

MongoDB also allows us to update individual documents using db.collection.UpdateOne(), or perform batch updates using db.collection.UpdateMany(). For example, to update the release year for Suits:

> db.series.updateOne(
{ name: "Suits" },
{
    $set: { year: 2010 }
}
)
{ "acknowledged" : true, "matchedCount" : 1, "modifiedCount" : 1 }

Finally, to delete documents, the Mongo Shell offers the db.collection.deleteOne() and db.collection.deleteMany() functions.

For instance, to delete all the series that premiered in 2012, we’d run:

> db.series.deleteMany({ year: 2012 })
{ "acknowledged" : true, "deletedCount" : 2 }

More information on the CRUD operations on MongoDB can be found in the online reference including more examples, performing operations with conditions, atomicity, and mapping of SQL concepts to MongoDB concepts and terminology.

Integrating Python with MongoDB

MongoDB provides drivers and tools for interacting with a MongoDB datastore using various programming languages including Python, JavaScript, Java, Go, and C#, among others.

PyMongo is the official MongoDB driver for Python, and we will use it to create a simple script that we will use to manipulate data stored in our SeriesDB database.

With Python 3.6+ and Virtualenv installed in our machines, let us create a virtual environment for our application and install PyMongo via pip:

$ virtualenv --python=python3 env --no-site-packages
$ source env/bin/activate
$ pip install pymongo

Using PyMongo, we are going to write a simple script that we can execute to perform different operations on our MongoDB database.

Connecting to MongoDB

First, we import pymongo in our mongo_db_script.py and create a client connected to our locally running instance of MongoDB:

import pymongo

# Create the client
client = MongoClient('localhost', 27017)

# Connect to our database
db = client['SeriesDB']

# Fetch our series collection
series_collection = db['series']

So far, we have created a client that connects to our MongoDB server and used it to fetch our ‘SeriesDB’ database. We then fetch our ‘series’ collection and store it in an object.

Creating Documents

To make our script more convenient, we will write functions that wrap around PyMongo to enable us to easily manipulate data. We will use Python dictionaries to represent documents and we will pass these dictionaries to our functions. First, let us create a function to insert data into our ‘series’ collection:

# Imports truncated for brevity

def insert_document(collection, data):
    """ Function to insert a document into a collection and
    return the document's id.
    """
    return collection.insert_one(data).inserted_id

This function receives a collection and a dictionary of data and inserts the data into the provided collection. The function then returns an identifier that we can use to accurately query the individual object from the database.

We should also note that MongoDB adds an additional _id key to our documents, when they are not provided, when creating the data.

Now let’s try adding a show using our function:

new_show = {
    "name": "FRIENDS",
    "year": 1994
}
print(insert_document(series_collection, new_show))

The output is:

5e4465cfdcbbdc68a6df233f

When we run our script, the _id of our new show is printed on the terminal and we can use this identifier to fetch the show later on.

We can provide an _id value instead of having it assigned automatically, which we’d provide in the dictionary:

new_show = {
    "_id": "1",
    "name": "FRIENDS",
    "year": 1994
}

And if we were to try and store a document with an existing _id, we’d be greeted with an error similar to the following:

DuplicateKeyError: E11000 duplicate key error index: SeriesDB.series.$id dup key: { : 1}

Retrieving Documents

To retrieve documents from the database we’ll use find_document(), which queries our collection for single or multiple documents. Our function will receive a dictionary that contains the elements we want to filter by, and an optional argument to specify whether we want one document or multiple documents:

# Imports and previous code truncated for brevity

def find_document(collection, elements, multiple=False):
    """ Function to retrieve single or multiple documents from a provided
    Collection using a dictionary containing a document's elements.
    """
    if multiple:
        results = collection.find(elements)
        return [r for r in results]
    else:
        return collection.find_one(elements)

And now, let’s use this function to find some documents:

result = find_document(series_collection, {'name': 'FRIENDS'})
print(result)

When executing our function, we did not provide the multiple parameter and the result is a single document:

{'_id': ObjectId('5e3031440597a8b07d2f4111'), 'name': 'FRIENDS', 'year': 1994}

When the multiple parameter is provided, the result is a list of all the documents in our collection that have a name attribute set to FRIENDS.

Updating Documents

Our next function, update_document(), will be used to update a single specific document. We will use the _id of the document and the collection it belongs to when locating it:

# Imports and previous code truncated for brevity

def update_document(collection, query_elements, new_values):
    """ Function to update a single document in a collection.
    """
    collection.update_one(query_elements, {'$set': new_values})

Now, let’s insert a document:

new_show = {
    "name": "FRIENDS",
    "year": 1995
}
id_ = insert_document(series_collection, new_show)

With that done, let’s update the document, which we’ll specify using the _id returned from adding it:

update_document(series_collection, {'_id': id_}, {'name': 'F.R.I.E.N.D.S'})

And finally, let’s fetch it to verify that the new value has been put in place and print the result:

result = find_document(series_collection, {'_id': id_})
print(result)

When we execute our script, we can see that our document has been updated:

{'_id': ObjectId('5e30378e96729abc101e3997'), 'name': 'F.R.I.E.N.D.S', 'year': 1995}

Deleting Documents

And finally, let’s write a function for deleting documents:

# Imports and previous code truncated for brevity

def delete_document(collection, query):
    """ Function to delete a single document from a collection.
    """
    collection.delete_one(query)

Since we’re using the delete_one method, only one document can be deleted per call, even if the query matches multiple documents.

Now, let’s use the function to delete an entry:

delete_document(series_collection, {'_id': id_})

If we try retrieving that same document:

result = find_document(series_collection, {'_id': id_})
print(result)

We’re greeted with the expected result:

None

Next Steps

We have highlighted and used a few of PyMongo’s methods to interact with our MongoDB server from a Python script. However, we have not utilized all the methods available to us through the module.

All the available methods can be found in the official PyMongo documentation and are classified according to the submodules.

We’ve written a simple script that performs rudimentary CRUD functionality on a MongoDB database. While we could import the functions in a more complex codebase, or into a Flask/Django application for example, these frameworks have libraries to achieve the same results already. These libraries make it easier, more conventient, and help us connect more securely to MongoDB.

For example, with Django we can use libraries such as Django MongoDB Engine and Djongo, while Flask has Flask-PyMongo that helps bridge the gap between Flask and PyMongo to facilitate seamless connectivity to a MongoDB database.

Conclusion

MongoDB is a document store and falls under the category of non-relational databases (NoSQL). It has certain advantages compared to relational databases, as well as some disadvantages.

While it is not suitable for all situations, we can still use MongoDB to store data and manipulate the data from our Python applications using PyMongo among other libraries - allowing us to harness the power of MongoDB in situations where it is best suited.

It is therefore up to us to carefully examine our requirements before making the decision to use MongoDB to store data.

The script we have written in this post can be found on GitHub.

#python #mongodb #databases

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How to integrate MongoDB with Python using PyMongo
Chloe  Butler

Chloe Butler

1667425440

Pdf2gerb: Perl Script Converts PDF Files to Gerber format

pdf2gerb

Perl script converts PDF files to Gerber format

Pdf2Gerb generates Gerber 274X photoplotting and Excellon drill files from PDFs of a PCB. Up to three PDFs are used: the top copper layer, the bottom copper layer (for 2-sided PCBs), and an optional silk screen layer. The PDFs can be created directly from any PDF drawing software, or a PDF print driver can be used to capture the Print output if the drawing software does not directly support output to PDF.

The general workflow is as follows:

  1. Design the PCB using your favorite CAD or drawing software.
  2. Print the top and bottom copper and top silk screen layers to a PDF file.
  3. Run Pdf2Gerb on the PDFs to create Gerber and Excellon files.
  4. Use a Gerber viewer to double-check the output against the original PCB design.
  5. Make adjustments as needed.
  6. Submit the files to a PCB manufacturer.

Please note that Pdf2Gerb does NOT perform DRC (Design Rule Checks), as these will vary according to individual PCB manufacturer conventions and capabilities. Also note that Pdf2Gerb is not perfect, so the output files must always be checked before submitting them. As of version 1.6, Pdf2Gerb supports most PCB elements, such as round and square pads, round holes, traces, SMD pads, ground planes, no-fill areas, and panelization. However, because it interprets the graphical output of a Print function, there are limitations in what it can recognize (or there may be bugs).

See docs/Pdf2Gerb.pdf for install/setup, config, usage, and other info.


pdf2gerb_cfg.pm

#Pdf2Gerb config settings:
#Put this file in same folder/directory as pdf2gerb.pl itself (global settings),
#or copy to another folder/directory with PDFs if you want PCB-specific settings.
#There is only one user of this file, so we don't need a custom package or namespace.
#NOTE: all constants defined in here will be added to main namespace.
#package pdf2gerb_cfg;

use strict; #trap undef vars (easier debug)
use warnings; #other useful info (easier debug)


##############################################################################################
#configurable settings:
#change values here instead of in main pfg2gerb.pl file

use constant WANT_COLORS => ($^O !~ m/Win/); #ANSI colors no worky on Windows? this must be set < first DebugPrint() call

#just a little warning; set realistic expectations:
#DebugPrint("${\(CYAN)}Pdf2Gerb.pl ${\(VERSION)}, $^O O/S\n${\(YELLOW)}${\(BOLD)}${\(ITALIC)}This is EXPERIMENTAL software.  \nGerber files MAY CONTAIN ERRORS.  Please CHECK them before fabrication!${\(RESET)}", 0); #if WANT_DEBUG

use constant METRIC => FALSE; #set to TRUE for metric units (only affect final numbers in output files, not internal arithmetic)
use constant APERTURE_LIMIT => 0; #34; #max #apertures to use; generate warnings if too many apertures are used (0 to not check)
use constant DRILL_FMT => '2.4'; #'2.3'; #'2.4' is the default for PCB fab; change to '2.3' for CNC

use constant WANT_DEBUG => 0; #10; #level of debug wanted; higher == more, lower == less, 0 == none
use constant GERBER_DEBUG => 0; #level of debug to include in Gerber file; DON'T USE FOR FABRICATION
use constant WANT_STREAMS => FALSE; #TRUE; #save decompressed streams to files (for debug)
use constant WANT_ALLINPUT => FALSE; #TRUE; #save entire input stream (for debug ONLY)

#DebugPrint(sprintf("${\(CYAN)}DEBUG: stdout %d, gerber %d, want streams? %d, all input? %d, O/S: $^O, Perl: $]${\(RESET)}\n", WANT_DEBUG, GERBER_DEBUG, WANT_STREAMS, WANT_ALLINPUT), 1);
#DebugPrint(sprintf("max int = %d, min int = %d\n", MAXINT, MININT), 1); 

#define standard trace and pad sizes to reduce scaling or PDF rendering errors:
#This avoids weird aperture settings and replaces them with more standardized values.
#(I'm not sure how photoplotters handle strange sizes).
#Fewer choices here gives more accurate mapping in the final Gerber files.
#units are in inches
use constant TOOL_SIZES => #add more as desired
(
#round or square pads (> 0) and drills (< 0):
    .010, -.001,  #tiny pads for SMD; dummy drill size (too small for practical use, but needed so StandardTool will use this entry)
    .031, -.014,  #used for vias
    .041, -.020,  #smallest non-filled plated hole
    .051, -.025,
    .056, -.029,  #useful for IC pins
    .070, -.033,
    .075, -.040,  #heavier leads
#    .090, -.043,  #NOTE: 600 dpi is not high enough resolution to reliably distinguish between .043" and .046", so choose 1 of the 2 here
    .100, -.046,
    .115, -.052,
    .130, -.061,
    .140, -.067,
    .150, -.079,
    .175, -.088,
    .190, -.093,
    .200, -.100,
    .220, -.110,
    .160, -.125,  #useful for mounting holes
#some additional pad sizes without holes (repeat a previous hole size if you just want the pad size):
    .090, -.040,  #want a .090 pad option, but use dummy hole size
    .065, -.040, #.065 x .065 rect pad
    .035, -.040, #.035 x .065 rect pad
#traces:
    .001,  #too thin for real traces; use only for board outlines
    .006,  #minimum real trace width; mainly used for text
    .008,  #mainly used for mid-sized text, not traces
    .010,  #minimum recommended trace width for low-current signals
    .012,
    .015,  #moderate low-voltage current
    .020,  #heavier trace for power, ground (even if a lighter one is adequate)
    .025,
    .030,  #heavy-current traces; be careful with these ones!
    .040,
    .050,
    .060,
    .080,
    .100,
    .120,
);
#Areas larger than the values below will be filled with parallel lines:
#This cuts down on the number of aperture sizes used.
#Set to 0 to always use an aperture or drill, regardless of size.
use constant { MAX_APERTURE => max((TOOL_SIZES)) + .004, MAX_DRILL => -min((TOOL_SIZES)) + .004 }; #max aperture and drill sizes (plus a little tolerance)
#DebugPrint(sprintf("using %d standard tool sizes: %s, max aper %.3f, max drill %.3f\n", scalar((TOOL_SIZES)), join(", ", (TOOL_SIZES)), MAX_APERTURE, MAX_DRILL), 1);

#NOTE: Compare the PDF to the original CAD file to check the accuracy of the PDF rendering and parsing!
#for example, the CAD software I used generated the following circles for holes:
#CAD hole size:   parsed PDF diameter:      error:
#  .014                .016                +.002
#  .020                .02267              +.00267
#  .025                .026                +.001
#  .029                .03167              +.00267
#  .033                .036                +.003
#  .040                .04267              +.00267
#This was usually ~ .002" - .003" too big compared to the hole as displayed in the CAD software.
#To compensate for PDF rendering errors (either during CAD Print function or PDF parsing logic), adjust the values below as needed.
#units are pixels; for example, a value of 2.4 at 600 dpi = .0004 inch, 2 at 600 dpi = .0033"
use constant
{
    HOLE_ADJUST => -0.004 * 600, #-2.6, #holes seemed to be slightly oversized (by .002" - .004"), so shrink them a little
    RNDPAD_ADJUST => -0.003 * 600, #-2, #-2.4, #round pads seemed to be slightly oversized, so shrink them a little
    SQRPAD_ADJUST => +0.001 * 600, #+.5, #square pads are sometimes too small by .00067, so bump them up a little
    RECTPAD_ADJUST => 0, #(pixels) rectangular pads seem to be okay? (not tested much)
    TRACE_ADJUST => 0, #(pixels) traces seemed to be okay?
    REDUCE_TOLERANCE => .001, #(inches) allow this much variation when reducing circles and rects
};

#Also, my CAD's Print function or the PDF print driver I used was a little off for circles, so define some additional adjustment values here:
#Values are added to X/Y coordinates; units are pixels; for example, a value of 1 at 600 dpi would be ~= .002 inch
use constant
{
    CIRCLE_ADJUST_MINX => 0,
    CIRCLE_ADJUST_MINY => -0.001 * 600, #-1, #circles were a little too high, so nudge them a little lower
    CIRCLE_ADJUST_MAXX => +0.001 * 600, #+1, #circles were a little too far to the left, so nudge them a little to the right
    CIRCLE_ADJUST_MAXY => 0,
    SUBST_CIRCLE_CLIPRECT => FALSE, #generate circle and substitute for clip rects (to compensate for the way some CAD software draws circles)
    WANT_CLIPRECT => TRUE, #FALSE, #AI doesn't need clip rect at all? should be on normally?
    RECT_COMPLETION => FALSE, #TRUE, #fill in 4th side of rect when 3 sides found
};

#allow .012 clearance around pads for solder mask:
#This value effectively adjusts pad sizes in the TOOL_SIZES list above (only for solder mask layers).
use constant SOLDER_MARGIN => +.012; #units are inches

#line join/cap styles:
use constant
{
    CAP_NONE => 0, #butt (none); line is exact length
    CAP_ROUND => 1, #round cap/join; line overhangs by a semi-circle at either end
    CAP_SQUARE => 2, #square cap/join; line overhangs by a half square on either end
    CAP_OVERRIDE => FALSE, #cap style overrides drawing logic
};
    
#number of elements in each shape type:
use constant
{
    RECT_SHAPELEN => 6, #x0, y0, x1, y1, count, "rect" (start, end corners)
    LINE_SHAPELEN => 6, #x0, y0, x1, y1, count, "line" (line seg)
    CURVE_SHAPELEN => 10, #xstart, ystart, x0, y0, x1, y1, xend, yend, count, "curve" (bezier 2 points)
    CIRCLE_SHAPELEN => 5, #x, y, 5, count, "circle" (center + radius)
};
#const my %SHAPELEN =
#Readonly my %SHAPELEN =>
our %SHAPELEN =
(
    rect => RECT_SHAPELEN,
    line => LINE_SHAPELEN,
    curve => CURVE_SHAPELEN,
    circle => CIRCLE_SHAPELEN,
);

#panelization:
#This will repeat the entire body the number of times indicated along the X or Y axes (files grow accordingly).
#Display elements that overhang PCB boundary can be squashed or left as-is (typically text or other silk screen markings).
#Set "overhangs" TRUE to allow overhangs, FALSE to truncate them.
#xpad and ypad allow margins to be added around outer edge of panelized PCB.
use constant PANELIZE => {'x' => 1, 'y' => 1, 'xpad' => 0, 'ypad' => 0, 'overhangs' => TRUE}; #number of times to repeat in X and Y directions

# Set this to 1 if you need TurboCAD support.
#$turboCAD = FALSE; #is this still needed as an option?

#CIRCAD pad generation uses an appropriate aperture, then moves it (stroke) "a little" - we use this to find pads and distinguish them from PCB holes. 
use constant PAD_STROKE => 0.3; #0.0005 * 600; #units are pixels
#convert very short traces to pads or holes:
use constant TRACE_MINLEN => .001; #units are inches
#use constant ALWAYS_XY => TRUE; #FALSE; #force XY even if X or Y doesn't change; NOTE: needs to be TRUE for all pads to show in FlatCAM and ViewPlot
use constant REMOVE_POLARITY => FALSE; #TRUE; #set to remove subtractive (negative) polarity; NOTE: must be FALSE for ground planes

#PDF uses "points", each point = 1/72 inch
#combined with a PDF scale factor of .12, this gives 600 dpi resolution (1/72 * .12 = 600 dpi)
use constant INCHES_PER_POINT => 1/72; #0.0138888889; #multiply point-size by this to get inches

# The precision used when computing a bezier curve. Higher numbers are more precise but slower (and generate larger files).
#$bezierPrecision = 100;
use constant BEZIER_PRECISION => 36; #100; #use const; reduced for faster rendering (mainly used for silk screen and thermal pads)

# Ground planes and silk screen or larger copper rectangles or circles are filled line-by-line using this resolution.
use constant FILL_WIDTH => .01; #fill at most 0.01 inch at a time

# The max number of characters to read into memory
use constant MAX_BYTES => 10 * M; #bumped up to 10 MB, use const

use constant DUP_DRILL1 => TRUE; #FALSE; #kludge: ViewPlot doesn't load drill files that are too small so duplicate first tool

my $runtime = time(); #Time::HiRes::gettimeofday(); #measure my execution time

print STDERR "Loaded config settings from '${\(__FILE__)}'.\n";
1; #last value must be truthful to indicate successful load


#############################################################################################
#junk/experiment:

#use Package::Constants;
#use Exporter qw(import); #https://perldoc.perl.org/Exporter.html

#my $caller = "pdf2gerb::";

#sub cfg
#{
#    my $proto = shift;
#    my $class = ref($proto) || $proto;
#    my $settings =
#    {
#        $WANT_DEBUG => 990, #10; #level of debug wanted; higher == more, lower == less, 0 == none
#    };
#    bless($settings, $class);
#    return $settings;
#}

#use constant HELLO => "hi there2"; #"main::HELLO" => "hi there";
#use constant GOODBYE => 14; #"main::GOODBYE" => 12;

#print STDERR "read cfg file\n";

#our @EXPORT_OK = Package::Constants->list(__PACKAGE__); #https://www.perlmonks.org/?node_id=1072691; NOTE: "_OK" skips short/common names

#print STDERR scalar(@EXPORT_OK) . " consts exported:\n";
#foreach(@EXPORT_OK) { print STDERR "$_\n"; }
#my $val = main::thing("xyz");
#print STDERR "caller gave me $val\n";
#foreach my $arg (@ARGV) { print STDERR "arg $arg\n"; }

Download Details:

Author: swannman
Source Code: https://github.com/swannman/pdf2gerb

License: GPL-3.0 license

#perl 

Ray  Patel

Ray Patel

1619510796

Lambda, Map, Filter functions in python

Welcome to my Blog, In this article, we will learn python lambda function, Map function, and filter function.

Lambda function in python: Lambda is a one line anonymous function and lambda takes any number of arguments but can only have one expression and python lambda syntax is

Syntax: x = lambda arguments : expression

Now i will show you some python lambda function examples:

#python #anonymous function python #filter function in python #lambda #lambda python 3 #map python #python filter #python filter lambda #python lambda #python lambda examples #python map

Shardul Bhatt

Shardul Bhatt

1626775355

Why use Python for Software Development

No programming language is pretty much as diverse as Python. It enables building cutting edge applications effortlessly. Developers are as yet investigating the full capability of end-to-end Python development services in various areas. 

By areas, we mean FinTech, HealthTech, InsureTech, Cybersecurity, and that's just the beginning. These are New Economy areas, and Python has the ability to serve every one of them. The vast majority of them require massive computational abilities. Python's code is dynamic and powerful - equipped for taking care of the heavy traffic and substantial algorithmic capacities. 

Programming advancement is multidimensional today. Endeavor programming requires an intelligent application with AI and ML capacities. Shopper based applications require information examination to convey a superior client experience. Netflix, Trello, and Amazon are genuine instances of such applications. Python assists with building them effortlessly. 

5 Reasons to Utilize Python for Programming Web Apps 

Python can do such numerous things that developers can't discover enough reasons to admire it. Python application development isn't restricted to web and enterprise applications. It is exceptionally adaptable and superb for a wide range of uses.

Robust frameworks 

Python is known for its tools and frameworks. There's a structure for everything. Django is helpful for building web applications, venture applications, logical applications, and mathematical processing. Flask is another web improvement framework with no conditions. 

Web2Py, CherryPy, and Falcon offer incredible capabilities to customize Python development services. A large portion of them are open-source frameworks that allow quick turn of events. 

Simple to read and compose 

Python has an improved sentence structure - one that is like the English language. New engineers for Python can undoubtedly understand where they stand in the development process. The simplicity of composing allows quick application building. 

The motivation behind building Python, as said by its maker Guido Van Rossum, was to empower even beginner engineers to comprehend the programming language. The simple coding likewise permits developers to roll out speedy improvements without getting confused by pointless subtleties. 

Utilized by the best 

Alright - Python isn't simply one more programming language. It should have something, which is the reason the business giants use it. Furthermore, that too for different purposes. Developers at Google use Python to assemble framework organization systems, parallel information pusher, code audit, testing and QA, and substantially more. Netflix utilizes Python web development services for its recommendation algorithm and media player. 

Massive community support 

Python has a steadily developing community that offers enormous help. From amateurs to specialists, there's everybody. There are a lot of instructional exercises, documentation, and guides accessible for Python web development solutions. 

Today, numerous universities start with Python, adding to the quantity of individuals in the community. Frequently, Python designers team up on various tasks and help each other with algorithmic, utilitarian, and application critical thinking. 

Progressive applications 

Python is the greatest supporter of data science, Machine Learning, and Artificial Intelligence at any enterprise software development company. Its utilization cases in cutting edge applications are the most compelling motivation for its prosperity. Python is the second most well known tool after R for data analytics.

The simplicity of getting sorted out, overseeing, and visualizing information through unique libraries makes it ideal for data based applications. TensorFlow for neural networks and OpenCV for computer vision are two of Python's most well known use cases for Machine learning applications.

Summary

Thinking about the advances in programming and innovation, Python is a YES for an assorted scope of utilizations. Game development, web application development services, GUI advancement, ML and AI improvement, Enterprise and customer applications - every one of them uses Python to its full potential. 

The disadvantages of Python web improvement arrangements are regularly disregarded by developers and organizations because of the advantages it gives. They focus on quality over speed and performance over blunders. That is the reason it's a good idea to utilize Python for building the applications of the future.

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How To Compare Tesla and Ford Company By Using Magic Methods in Python

Magic Methods are the special methods which gives us the ability to access built in syntactical features such as ‘<’, ‘>’, ‘==’, ‘+’ etc…

You must have worked with such methods without knowing them to be as magic methods. Magic methods can be identified with their names which start with __ and ends with __ like init, call, str etc. These methods are also called Dunder Methods, because of their name starting and ending with Double Underscore (Dunder).

Now there are a number of such special methods, which you might have come across too, in Python. We will just be taking an example of a few of them to understand how they work and how we can use them.

1. init

class AnyClass:
    def __init__():
        print("Init called on its own")
obj = AnyClass()

The first example is _init, _and as the name suggests, it is used for initializing objects. Init method is called on its own, ie. whenever an object is created for the class, the init method is called on its own.

The output of the above code will be given below. Note how we did not call the init method and it got invoked as we created an object for class AnyClass.

Init called on its own

2. add

Let’s move to some other example, add gives us the ability to access the built in syntax feature of the character +. Let’s see how,

class AnyClass:
    def __init__(self, var):
        self.some_var = var
    def __add__(self, other_obj):
        print("Calling the add method")
        return self.some_var + other_obj.some_var
obj1 = AnyClass(5)
obj2 = AnyClass(6)
obj1 + obj2

#python3 #python #python-programming #python-web-development #python-tutorials #python-top-story #python-tips #learn-python

Sival Alethea

Sival Alethea

1624395600

MongoDB with Python Crash Course - Tutorial for Beginners. DO NOT MISS!!!

Learn the most popular NoSQL / document database: MongoDB. In this quickstart tutorial, you’ll be up and running with MongoDB and Python.
⭐️Course Contents⭐️
⌨️ (0:00:00) Welcome
⌨️ (0:04:33) Intro to MongoDB
⌨️ (0:07:49) How do document DBs work?
⌨️ (0:10:34) Who uses MongoDB
⌨️ (0:13:02) Data modeling
⌨️ (0:16:30) Modeling guidelines
⌨️ (0:22:11) Integration database
⌨️ (0:24:23) Getting demo code
⌨️ (0:30:07) How ODMs work?
⌨️ (0:32:55) Introduction to mongoengine
⌨️ (0:34:01) Demo: Registering connections with MongoEngine
⌨️ (0:37:20) Concept: Registering connections
⌨️ (0:39:14) Demo: Defining mongoengine entities (classes)
⌨️ (0:45:22) Concept: mongoengine entities
⌨️ (0:49:03) Demo: Create a new account
⌨️ (0:56:55) Demo: Robo 3T for viewing and managing data
⌨️ (0:58:18) Demo: Login
⌨️ (1:00:07) Demo: Register a cage
⌨️ (1:10:28) Demo: Add a bookable time as a host
⌨️ (1:16:13) Demo: Managing your snakes as a guest
⌨️ (1:19:18) Demo: Book a cage as a guest
⌨️ (1:33:41) Demo: View your bookings as guest
⌨️ (1:41:29) Demo: View bookings as host
⌨️ (1:46:18) Concept: Inserting documents
⌨️ (1:47:28) Concept: Queries
⌨️ (1:48:09) Concept: Querying subdocuments with mongoengine
⌨️ (1:49:37) Concept: Query using operators
⌨️ (1:50:24) Concept: Updating via whole documents
⌨️ (1:51:46) Concept: Updating via in-place operators
⌨️ (1:54:01) Conclusion

📺 The video in this post was made by freeCodeCamp.org
The origin of the article: https://www.youtube.com/watch?v=E-1xI85Zog8&list=PLWKjhJtqVAbnqBxcdjVGgT3uVR10bzTEB&index=10
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