How to install Python packages with pipenv, venv or virtualenv package manager

You can find GitHub repository in https://github.com/python-projects-kenanhancer/python_demo

  • Pyenv – Python Runtime Version Manager
  • Pipenv – Python Package Manager and Virtual environment manager
  • Venv – Virtual environment manager
  • Virtualenv – Virtual environment manager

Installing Python Runtime Versions via Pyenv

In order to test different Python Runtime versions, I have installed some versions.

$ pyenv install 3.10.2

python-build: use openssl@1.1 from homebrew
python-build: use readline from homebrew
Downloading Python-3.10.2.tar.xz...
-> https://www.python.org/ftp/python/3.10.2/Python-3.10.2.tar.xz
Installing Python-3.10.2...
python-build: use tcl-tk from homebrew
python-build: use readline from homebrew
python-build: use zlib from xcode sdk
Installed Python-3.10.2 to /Users/kenanhancer/.pyenv/versions/3.10.2

I have 4 Python runtime versions(3.10.2, 3.10.3, 3.10.4, 3.10.5) in my machine.

$ pyenv versions

  system
  3.10.2
  3.10.3
  3.10.4
* 3.10.5 (set by /Users/kenanhancer/.pyenv/version)
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TypeScript Recursive Type

Below two code blocks are doing same job and the only difference is below second code block uses variadic tuple. Check the below links for more details.

https://www.typescriptlang.org/docs/handbook/release-notes/typescript-3-7.html#more-recursive-type-aliases

https://www.typescriptlang.org/docs/handbook/release-notes/typescript-4-1.html#recursive-conditional-types

type CompareLength<Left extends any[], Right extends any[]> =
    Left['length'] extends Right['length'] ? 'equal' :
    Left extends [] ? 'shorterLeft' :
    Right extends [] ? 'shorterRight' :
    ((..._: Left) => any) extends ((_: any, ..._1: infer LeftRest) => any) ?
    ((..._: Right) => any) extends ((_: any, ..._1: infer RightRest) => any) ?
    CompareLength<LeftRest, RightRest> :
    never :
    never;

type T1 = CompareLength<[firstName: string], [lastName: string]>;

type T2 = CompareLength<[firstName: string], [lastName: string, age: number]>;

type T3 = CompareLength<[firstName: string, age: number], [lastName: string]>;
type CompareLength<Left extends any[], Right extends any[]> =
    Left['length'] extends Right['length'] ? 'equal' :
    Left extends [] ? 'shorterLeft' :
    Right extends [] ? 'shorterRight' :
    Left extends [any, ...infer L] ? 
    Right extends [any, ...infer R] ? 
    CompareLength<L, R> :
    never :
    never;

type T1 = CompareLength<[firstName: string], [lastName: string]>;

type T2 = CompareLength<[firstName: string], [lastName: string, age: number]>;

type T3 = CompareLength<[firstName: string, age: number], [lastName: string]>;

TypeScript Exhaustiveness Checking Part 2

type HttpMethod = "GET" | "POST" | "PUT" | "DELETE";

const sendRequest = (url: string, method: HttpMethod) => {
    switch (method) {
        case 'DELETE':

            break;
        case 'GET':

            break;
        case 'POST':

            break;
        case 'PUT':

            break;
        default:
            const exhaustiveCheck: never = method; // ✅ no error
            throw new Error(`Unhandled case: ${exhaustiveCheck}`);
    }
};
type Fruit = 'banana' | 'orange' | 'mango';

function exhaustiveCheck(param: never): never {
    throw new Error('should not reach here')
}

function makeDessert(fruit: Fruit) {
    switch (fruit) {
        case 'banana': return 'Banana Shake'
        case 'orange': return 'Orange Juice'
    }
    exhaustiveCheck(fruit) // 🚫 ERROR! `mango` is not assignable
}
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TypeScript Exhaustiveness Checking

Exhaustiveness checking is a good feature when you use switch block. Assume that you need to check a value of variable which data type is union type as shown below screenshot.

Shape is a discriminated union which consists of three types named Circle, Square and Triangle.

kind field is shared in Circle, Square and Triangle types so that if developer forgets to use any of kind field value in switch block, TypeScript will error in coding-time.

Notice that there is a red line in line 347, it is due to missing triangle case in switch block.

This is the error shown in the code.

After adding triangle case in line 346, the error disappeared.

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TypeScript Language Basics

Primitive Types (Boolean, Number, String)

Boolean

let isDone: boolean = false;

Number

let decimal: number = 6;
let hex: number = 0xf00d;
let binary: number = 0b1010;
let octal: number = 0o744;
let big: bigint = 100n;

String

let color: string = "blue";

let fullName: string = 'Bob Bobbington';

let age: number = 37;

let sentence: string = `Hello, my name is ${fullName}.
 
I'll be ${age + 1} years old next month.`;

Arrays

let list: number[] = [1, 2, 3];

let list2: Array<number> = [1, 2, 3];
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