1651954860

Comfy Table: A Library for Building Beautiful Tables

Comfy-table

Comfy-table is designed as a library for building beautiful tables, while being easy to use.

Features

Dynamic arrangement of content depending on a given width.
ANSI content styling for terminals (Colors, Bold, Blinking, etc.).
Styling Presets and preset modifiers to get you started.
Pretty much every part of the table is customizable (borders, lines, padding, alignment).
Constraints on columns that allow some additional control over how to arrange content.
Cross plattform (Linux, macOS, Windows).
It's fast enough.
- Benchmarks show that a pretty big table with complex constraints is build in 470μs or ~0.5ms.
- The table seen at the top of the readme takes ~30μs.
- These numbers are from a overclocked i7-8700K with a max single-core performance of 4.9GHz.
- To run the benchmarks yourselves, install criterion via cargo install cargo-criterion and run cargo criterion afterwards.

Comfy-table is written for the current stable Rust version. Older Rust versions may work but aren't officially supported.

Examples

use comfy_table::Table;

fn main() {
    let mut table = Table::new();
    table
        .set_header(vec!["Header1", "Header2", "Header3"])
        .add_row(vec![
                 "This is a text",
                 "This is another text",
                 "This is the third text",
        ])
        .add_row(vec![
                 "This is another text",
                 "Now\nadd some\nmulti line stuff",
                 "This is awesome",
        ]);

    println!("{table}");
}

Create a very basic table.
This table will become as wide as your content. Nothing fancy happening here.

+----------------------+----------------------+------------------------+
| Header1              | Header2              | Header3                |
+======================================================================+
| This is a text       | This is another text | This is the third text |
|----------------------+----------------------+------------------------|
| This is another text | Now                  | This is awesome        |
|                      | add some             |                        |
|                      | multi line stuff     |                        |
+----------------------+----------------------+------------------------+

More Features

use comfy_table::*;
use comfy_table::presets::UTF8_FULL;
use comfy_table::modifiers::UTF8_ROUND_CORNERS;

fn main() {
    let mut table = Table::new();
    table
        .load_preset(UTF8_FULL)
        .apply_modifier(UTF8_ROUND_CORNERS)
        .set_content_arrangement(ContentArrangement::Dynamic)
        .set_width(40)
        .set_header(vec!["Header1", "Header2", "Header3"])
        .add_row(vec![
                 Cell::new("Center aligned").set_alignment(CellAlignment::Center),
                 Cell::new("This is another text"),
                 Cell::new("This is the third text"),
        ])
        .add_row(vec![
                 "This is another text",
                 "Now\nadd some\nmulti line stuff",
                 "This is awesome",
        ]);

    // Set the default alignment for the third column to right
    let column = table.column_mut(2).expect("Our table has three columns");
    column.set_cell_alignment(CellAlignment::Right);

    println!("{table}");
}

Create a table with UTF8 styling, and apply a modifier that gives the table round corners.
Additionally, the content will dynamically wrap to maintain a given table width.
If the table width isn't explicitely set and the program runs in a terminal, the terminal size will be used.

On top of this, we set the default alignment for the right column to Right and the alignment of the left top cell to Center.

╭────────────┬────────────┬────────────╮
│ Header1    ┆ Header2    ┆    Header3 │
╞════════════╪════════════╪════════════╡
│  This is a ┆ This is    ┆    This is │
│    text    ┆ another    ┆  the third │
│            ┆ text       ┆       text │
├╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌┤
│ This is    ┆ Now        ┆    This is │
│ another    ┆ add some   ┆    awesome │
│ text       ┆ multi line ┆            │
│            ┆ stuff      ┆            │
╰────────────┴────────────┴────────────╯

Styling

use comfy_table::*;
use comfy_table::presets::UTF8_FULL;

fn main() {
    let mut table = Table::new();
    table.load_preset(UTF8_FULL)
        .set_content_arrangement(ContentArrangement::Dynamic)
        .set_width(80)
        .set_header(vec![
                    Cell::new("Header1").add_attribute(Attribute::Bold),
                    Cell::new("Header2").fg(Color::Green),
                    Cell::new("Header3"),
        ])
        .add_row(vec![
                 Cell::new("This is a bold text").add_attribute(Attribute::Bold),
                 Cell::new("This is a green text").fg(Color::Green),
                 Cell::new("This one has black background").bg(Color::Black),
        ])
        .add_row(vec![
                 Cell::new("Blinky boi").add_attribute(Attribute::SlowBlink),
                 Cell::new("This table's content is dynamically arranged. The table is exactly 80 characters wide.\nHere comes a reallylongwordthatshoulddynamicallywrap"),
                 Cell::new("COMBINE ALL THE THINGS")
                 .fg(Color::Green)
                 .bg(Color::Black)
                 .add_attributes(vec![
                                 Attribute::Bold,
                                 Attribute::SlowBlink,
                 ])
        ]);

    println!("{table}");
}

This code generates the table that can be seen at the top of this document.

Code Examples

A few examples can be found in the example folder. To test an example, run cargo run --example $name. E.g.:

cargo run --example readme_table

If you're looking for more information, take a look at the tests folder.
There are tests for almost every feature including a visual view for each resulting table.

Contribution Guidelines

Comfy-table is supposed to be minimalistic. A fixed set of features that just work for "normal" use-cases:

Normal tables (columns, rows, one cell per column/row).
Dynamic arrangement of content to a given width.
Some kind of manual intervention in the arrangement process.

If you come up with an idea or an improvement that fits into the current scope of the project, feel free to create an issue :)!

Some things however will most likely not be added to the project since they drastically increase the complexity of the library or cover very specific edge-cases.

Such features are:

Nested tables
Cells that span over multiple columns/rows
CSV to table conversion and vice versa

Unsafe

Comfy-table doesn't allow unsafe code in its code-base. As it's a "simple" formatting library it also shouldn't be needed in the future.

However, Comfy-table uses two unsafe functions calls in its dependencies.
Both calls can be disabled by explicitely calling Table::force_no_tty.

Furthermore, all terminal related functionality, including styling, can be disabled by excluding the tty feature flag. Without this flag no unsafe code is used as far as I know.

crossterm::tty::IsTty. This function is necessary to detect whether we're currently on a tty or not. This is only called if no explicit width is provided via Table::set_width.

/// On unix the `isatty()` function returns true if a file
/// descriptor is a terminal.
#[cfg(unix)]
impl<S: AsRawFd> IsTty for S {
    fn is_tty(&self) -> bool {
        let fd = self.as_raw_fd();
        unsafe { libc::isatty(fd) == 1 }
    }
}

2. crossterm::terminal::size. This function is necessary to detect the current terminal width if we're on a tty. This is only called if no explicit width is provided via Table::set_width.

http://rosettacode.org/wiki/Terminal_control/Dimensions#Library:_BSD_libc This is another libc call which is used to communicate with /dev/tty via a file descriptor.

...
if wrap_with_result(unsafe { ioctl(fd, TIOCGWINSZ.into(), &mut size) }).is_ok() {
    Ok((size.ws_col, size.ws_row))
} else {
    tput_size().ok_or_else(|| std::io::Error::last_os_error().into())
}
...

Download Details:
Author: nukesor
Source Code: https://github.com/nukesor/comfy-table
License: MIT license

#rust #rustlang #commandline

What is GEEK

Buddha Community

Comfy Table: A Library for Building Beautiful Tables

AppClues Infotech

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Best Beauty Salon App Development Company

Do you want to build a superior beauty salon mobile app for your business? Then AppClues Infotech is a professional mobile app development company that works with a hair salon, Spa, and other businesses in the beauty industry.

Being the premier beauty salon mobile app development company we render quality solutions by making use of innovative thoughts. Our accomplished techies are adept at designing the feasible solutions that are affordable and cost-effective.

For more info:
Call: +1-978-309-9910
Email: info@appcluesinfotech.com

#how to build a mobile app for beauty salon #beauty salon app development company #best beauty salon app development company #top beauty salon app development company #create a beauty salon mobile app

Chatbot Library

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The Best Way to Build a Chatbot in 2021

A useful tool several businesses implement for answering questions that potential customers may have is a chatbot. Many programming languages give web designers several ways on how to make a chatbot for their websites. They are capable of answering basic questions for visitors and offer innovation for businesses.

With the help of programming languages, it is possible to create a chatbot from the ground up to satisfy someone’s needs.

Plan Out the Chatbot’s Purpose

Before building a chatbot, it is ideal for web designers to determine how it will function on a website. Several chatbot duties center around fulfilling customers’ needs and questions or compiling and optimizing data via transactions.

Some benefits of implementing chatbots include:

Generating leads for marketing products and services
Improve work capacity when employees cannot answer questions or during non-business hours
Reducing errors while providing accurate information to customers or visitors
Meeting customer demands through instant communication
Alerting customers about their online transactions

Some programmers may choose to design a chatbox to function through predefined answers based on the questions customers may input or function by adapting and learning via human input.

#chatbots #latest news #the best way to build a chatbot in 2021 #build #build a chatbot #best way to build a chatbot

Fredy Larson

1595209620

How to alter tables in production when records are in millions

As a developer, I have experienced changes in app when it is in production and the records have grown up to millions. In this specific case if you want to alter a column using simple migrations that will not work because of the following reasons:

It is not so easy if your production servers are under heavy load and the database tables have 100 million rows. Because such a migration will run for some seconds or even minutes and the database table can be locked for this time period – a no-go on a zero-downtime environment.

In this specific case you can use MySQL’s algorithms: Online DDL operations. That’s how you can do it in Laravel.

First of all create migration. For example I want to modify a column’s name the traditional migration will be:

Schema::table('users', function (Blueprint $table) {
            $table->renameColumn('name', 'first_name');
        });

Run the following command php artisan migrate –pretend this command will not run the migration rather it will print out it’s raw sql:

ALTER TABLE users CHANGE name first_name VARCHAR(191) NOT NULL

Copy that raw sql, remove following code:

Schema::table('users', function (Blueprint $table) {
            $table->renameColumn('name', 'first_name');
        });

Replace it with following in migrations up method:

\DB::statement('ALTER TABLE users CHANGE name first_name VARCHAR(191) NOT NULL');

Add desired algorithm, in my case query will look like this:

\DB::statement('ALTER TABLE users CHANGE name first_name VARCHAR(191) NOT NULL, ALGORITHM=INPLACE, LOCK=NONE;');

#laravel #mysql #php #alter heavy tables in production laravel #alter table in production laravel #alter tables with million of records in laravel #how to alter heavy table in production laravel #how to alter table in production larave #mysql online ddl operations

Riyad Amin

1571046022

Build Your Own Cryptocurrency Blockchain in Python

Cryptocurrency is a decentralized digital currency that uses encryption techniques to regulate the generation of currency units and to verify the transfer of funds. Anonymity, decentralization, and security are among its main features. Cryptocurrency is not regulated or tracked by any centralized authority, government, or bank.

Blockchain, a decentralized peer-to-peer (P2P) network, which is comprised of data blocks, is an integral part of cryptocurrency. These blocks chronologically store information about transactions and adhere to a protocol for inter-node communication and validating new blocks. The data recorded in blocks cannot be altered without the alteration of all subsequent blocks.

In this article, we are going to explain how you can create a simple blockchain using the Python programming language.

Here is the basic blueprint of the Python class we’ll use for creating the blockchain:

class Block(object):
    def __init__():
        pass
    #initial structure of the block class 
    def compute_hash():
        pass
    #producing the cryptographic hash of each block 
  class BlockChain(object):
    def __init__(self):
    #building the chain
    def build_genesis(self):
        pass
    #creating the initial block
    def build_block(self, proof_number, previous_hash):
        pass
    #builds new block and adds to the chain
   @staticmethod
    def confirm_validity(block, previous_block):
        pass
    #checks whether the blockchain is valid
    def get_data(self, sender, receiver, amount):
        pass
    # declares data of transactions
    @staticmethod
    def proof_of_work(last_proof):
        pass
    #adds to the security of the blockchain
    @property
    def latest_block(self):
        pass
    #returns the last block in the chain

Now, let’s explain how the blockchain class works.

Initial Structure of the Block Class

Here is the code for our initial block class:

import hashlib
import time
class Block(object):
    def __init__(self, index, proof_number, previous_hash, data, timestamp=None):
        self.index = index
        self.proof_number = proof_number
        self.previous_hash = previous_hash
        self.data = data
        self.timestamp = timestamp or time.time()
    @property
    def compute_hash(self):
        string_block = "{}{}{}{}{}".format(self.index, self.proof_number, self.previous_hash, self.data, self.timestamp)
        return hashlib.sha256(string_block.encode()).hexdigest()

As you can see above, the class constructor or initiation method ( init()) above takes the following parameters:

self — just like any other Python class, this parameter is used to refer to the class itself. Any variable associated with the class can be accessed using it.

index — it’s used to track the position of a block within the blockchain.

previous_hash — it used to reference the hash of the previous block within the blockchain.

data—it gives details of the transactions done, for example, the amount bought.

timestamp—it inserts a timestamp for all the transactions performed.

The second method in the class, compute_hash , is used to produce the cryptographic hash of each block based on the above values.

As you can see, we imported the SHA-256 algorithm into the cryptocurrency blockchain project to help in getting the hashes of the blocks.

Once the values have been placed inside the hashing module, the algorithm will return a 256-bit string denoting the contents of the block.

So, this is what gives the blockchain immutability. Since each block will be represented by a hash, which will be computed from the hash of the previous block, corrupting any block in the chain will make the other blocks have invalid hashes, resulting in breakage of the whole blockchain network.

Building the Chain

The whole concept of a blockchain is based on the fact that the blocks are “chained” to each other. Now, we’ll create a blockchain class that will play the critical role of managing the entire chain.

It will keep the transactions data and include other helper methods for completing various roles, such as adding new blocks.

Let’s talk about the helper methods.

Adding the Constructor Method

Here is the code:

class BlockChain(object):
    def __init__(self):
        self.chain = []
        self.current_data = []
        self.nodes = set()
        self.build_genesis()

The init() constructor method is what instantiates the blockchain.

Here are the roles of its attributes:

self.chain — this variable stores all the blocks.

self.current_data — this variable stores information about the transactions in the block.

self.build_genesis() — this method is used to create the initial block in the chain.

Building the Genesis Block

The build_genesis() method is used for creating the initial block in the chain, that is, a block without any predecessors. The genesis block is what represents the beginning of the blockchain.

To create it, we’ll call the build_block() method and give it some default values. The parameters proof_number and previous_hash are both given a value of zero, though you can give them any value you desire.

Here is the code:

def build_genesis(self):
        self.build_block(proof_number=0, previous_hash=0)
 def build_block(self, proof_number, previous_hash):
        block = Block(
            index=len(self.chain),
            proof_number=proof_number,
            previous_hash=previous_hash,
            data=self.current_data
        )
        self.current_data = []  
        self.chain.append(block)
        return block

Confirming Validity of the Blockchain

The confirm_validity method is critical in examining the integrity of the blockchain and making sure inconsistencies are lacking.

As explained earlier, hashes are pivotal for realizing the security of the cryptocurrency blockchain, because any slight alteration in an object will result in the creation of an entirely different hash.

Thus, the confirm_validity method utilizes a series of if statements to assess whether the hash of each block has been compromised.

Furthermore, it also compares the hash values of every two successive blocks to identify any anomalies. If the chain is working properly, it returns true; otherwise, it returns false.

Here is the code:

def confirm_validity(block, previous_block):
        if previous_block.index + 1 != block.index:
            return False
        elif previous_block.compute_hash != block.previous_hash:
            return False
        elif block.timestamp <= previous_block.timestamp:
            return False
        return True

Declaring Data of Transactions

The get_data method is important in declaring the data of transactions on a block. This method takes three parameters (sender’s information, receiver’s information, and amount) and adds the transaction data to the self.current_data list.

Here is the code:

def get_data(self, sender, receiver, amount):
        self.current_data.append({
            'sender': sender,
            'receiver': receiver,
            'amount': amount
        })
        return True

Effecting the Proof of Work

In blockchain technology, Proof of Work (PoW) refers to the complexity involved in mining or generating new blocks on the blockchain.

For example, the PoW can be implemented by identifying a number that solves a problem whenever a user completes some computing work. Anyone on the blockchain network should find the number complex to identify but easy to verify — this is the main concept of PoW.

This way, it discourages spamming and compromising the integrity of the network.

In this article, we’ll illustrate how to include a Proof of Work algorithm in a blockchain cryptocurrency project.

Finalizing With the Last Block

Finally, the latest_block() helper method is used for retrieving the last block on the network, which is actually the current block.

Here is the code:

def latest_block(self):
        return self.chain[-1]

Implementing Blockchain Mining

Now, this is the most exciting section!

Initially, the transactions are kept in a list of unverified transactions. Mining refers to the process of placing the unverified transactions in a block and solving the PoW problem. It can be referred to as the computing work involved in verifying the transactions.

If everything has been figured out correctly, a block is created or mined and joined together with the others in the blockchain. If users have successfully mined a block, they are often rewarded for using their computing resources to solve the PoW problem.

Here is the mining method in this simple cryptocurrency blockchain project:

def block_mining(self, details_miner):
            self.get_data(
            sender="0", #it implies that this node has created a new block
            receiver=details_miner,
            quantity=1, #creating a new block (or identifying the proof number) is awarded with 1
        )
        last_block = self.latest_block
        last_proof_number = last_block.proof_number
        proof_number = self.proof_of_work(last_proof_number)
        last_hash = last_block.compute_hash
        block = self.build_block(proof_number, last_hash)
        return vars(block)

Summary

Here is the whole code for our crypto blockchain class in Python:

import hashlib
import time
class Block(object):
    def __init__(self, index, proof_number, previous_hash, data, timestamp=None):
        self.index = index
        self.proof_number = proof_number
        self.previous_hash = previous_hash
        self.data = data
        self.timestamp = timestamp or time.time()
    @property
    def compute_hash(self):
        string_block = "{}{}{}{}{}".format(self.index, self.proof_number, self.previous_hash, self.data, self.timestamp)
        return hashlib.sha256(string_block.encode()).hexdigest()
    def __repr__(self):
        return "{} - {} - {} - {} - {}".format(self.index, self.proof_number, self.previous_hash, self.data, self.timestamp)
class BlockChain(object):
    def __init__(self):
        self.chain = []
        self.current_data = []
        self.nodes = set()
        self.build_genesis()
    def build_genesis(self):
        self.build_block(proof_number=0, previous_hash=0)
    def build_block(self, proof_number, previous_hash):
        block = Block(
            index=len(self.chain),
            proof_number=proof_number,
            previous_hash=previous_hash,
            data=self.current_data
        )
        self.current_data = []  
        self.chain.append(block)
        return block
    @staticmethod
    def confirm_validity(block, previous_block):
        if previous_block.index + 1 != block.index:
            return False
        elif previous_block.compute_hash != block.previous_hash:
            return False
        elif block.timestamp <= previous_block.timestamp:
            return False
        return True
    def get_data(self, sender, receiver, amount):
        self.current_data.append({
            'sender': sender,
            'receiver': receiver,
            'amount': amount
        })
        return True        
    @staticmethod
    def proof_of_work(last_proof):
        pass
    @property
    def latest_block(self):
        return self.chain[-1]
    def chain_validity(self):
        pass        
    def block_mining(self, details_miner):       
        self.get_data(
            sender="0", #it implies that this node has created a new block
            receiver=details_miner,
            quantity=1, #creating a new block (or identifying the proof number) is awared with 1
        )
        last_block = self.latest_block
        last_proof_number = last_block.proof_number
        proof_number = self.proof_of_work(last_proof_number)
        last_hash = last_block.compute_hash
        block = self.build_block(proof_number, last_hash)
        return vars(block)  
    def create_node(self, address):
        self.nodes.add(address)
        return True
    @staticmethod
    def get_block_object(block_data):        
        return Block(
            block_data['index'],
            block_data['proof_number'],
            block_data['previous_hash'],
            block_data['data'],
            timestamp=block_data['timestamp']
        )
blockchain = BlockChain()
print("GET READY MINING ABOUT TO START")
print(blockchain.chain)
last_block = blockchain.latest_block
last_proof_number = last_block.proof_number
proof_number = blockchain.proof_of_work(last_proof_number)
blockchain.get_data(
    sender="0", #this means that this node has constructed another block
    receiver="LiveEdu.tv", 
    amount=1, #building a new block (or figuring out the proof number) is awarded with 1
)
last_hash = last_block.compute_hash
block = blockchain.build_block(proof_number, last_hash)
print("WOW, MINING HAS BEEN SUCCESSFUL!")
print(blockchain.chain)

Now, let’s try to run our code to see if we can generate some digital coins…

Wow, it worked!

Conclusion

That is it!

We hope that this article has assisted you to understand the underlying technology that powers cryptocurrencies such as Bitcoin and Ethereum.

We just illustrated the basic ideas for making your feet wet in the innovative blockchain technology. The project above can still be enhanced by incorporating other features to make it more useful and robust.

Learn More

Thanks for reading !

Do you have any comments or questions? Please share them below.

#python #cryptocurrency

Awesome Rust

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