Python's operator.not_ in TypeScript

How to use

Install via yarn add locutus and import: import { not_ } from 'locutus/python/operator/not_'.

Or with CommonJS: const { not_ } = require('locutus/python/operator/not_')

Use a bundler that supports tree-shaking so you only ship the functions you actually use. Vite, webpack, Rollup, and Parcel all handle this. For server-side use this is less of a concern.

Examples

These examples are extracted from test cases that automatically verify our functions against their native counterparts.

#	code	expected result
1	not_([])	true
2	not_(NaN)	false

Notes

• Uses Python truthiness rules instead of raw JS Boolean coercion.

Dependencies

This function uses the following Locutus functions:

• _operator (python/_helpers)

Here's what our current TypeScript equivalent to Python's operator.not_ looks like.

TSTypeScript JSJavaScript TSStandalone TS JSStandalone JS

Copy code

import { pythonNot } from '../_helpers/_operator.ts'

export function not_(a: unknown): boolean {
  //      discuss at: https://locutus.io/python/operator/not_/
  // parity verified: Python 3.12
  //     original by: Kevin van Zonneveld (https://kvz.io)
  //          note 1: Uses Python truthiness rules instead of raw JS Boolean coercion.
  //       example 1: not_([])
  //       returns 1: true
  //       example 2: not_(NaN)
  //       returns 2: false

  return pythonNot(a)
}

import { pythonNot } from '../_helpers/_operator.ts'

export function not_(a) {
  //      discuss at: https://locutus.io/python/operator/not_/
  // parity verified: Python 3.12
  //     original by: Kevin van Zonneveld (https://kvz.io)
  //          note 1: Uses Python truthiness rules instead of raw JS Boolean coercion.
  //       example 1: not_([])
  //       returns 1: true
  //       example 2: not_(NaN)
  //       returns 2: false

  return pythonNot(a)
}

// python/_helpers/_operator (Locutus helper dependency)
type PythonMapping = { [key: string]: unknown }

function pythonTruth(value: unknown): boolean {
  if (value === null || value === undefined) {
    return false
  }

  if (typeof value === 'boolean') {
    return value
  }

  if (typeof value === 'number') {
    return value !== 0
  }

  if (typeof value === 'bigint') {
    return value !== 0n
  }

  if (typeof value === 'string') {
    return value.length > 0
  }

  if (Array.isArray(value)) {
    return value.length > 0
  }

  if (value instanceof Set || value instanceof Map) {
    return value.size > 0
  }

  if (isPythonMapping(value)) {
    return Object.keys(value).length > 0
  }

  return true
}

function pythonNot(value: unknown): boolean {
  return !pythonTruth(value)
}

function isPythonMapping(value: unknown): value is PythonMapping {
  if (typeof value !== 'object' || value === null || Array.isArray(value)) {
    return false
  }

  return Object.prototype.toString.call(value) === '[object Object]'
}

// python/operator/not_ (target function module)
function not_(a: unknown): boolean {
  //      discuss at: https://locutus.io/python/operator/not_/
  // parity verified: Python 3.12
  //     original by: Kevin van Zonneveld (https://kvz.io)
  //          note 1: Uses Python truthiness rules instead of raw JS Boolean coercion.
  //       example 1: not_([])
  //       returns 1: true
  //       example 2: not_(NaN)
  //       returns 2: false

  return pythonNot(a)
}

// python/_helpers/_operator (Locutus helper dependency)
function pythonTruth(value) {
  if (value === null || value === undefined) {
    return false
  }

  if (typeof value === 'boolean') {
    return value
  }

  if (typeof value === 'number') {
    return value !== 0
  }

  if (typeof value === 'bigint') {
    return value !== 0n
  }

  if (typeof value === 'string') {
    return value.length > 0
  }

  if (Array.isArray(value)) {
    return value.length > 0
  }

  if (value instanceof Set || value instanceof Map) {
    return value.size > 0
  }

  if (isPythonMapping(value)) {
    return Object.keys(value).length > 0
  }

  return true
}

function pythonNot(value) {
  return !pythonTruth(value)
}

function isPythonMapping(value) {
  if (typeof value !== 'object' || value === null || Array.isArray(value)) {
    return false
  }

  return Object.prototype.toString.call(value) === '[object Object]'
}

// python/operator/not_ (target function module)
function not_(a) {
  //      discuss at: https://locutus.io/python/operator/not_/
  // parity verified: Python 3.12
  //     original by: Kevin van Zonneveld (https://kvz.io)
  //          note 1: Uses Python truthiness rules instead of raw JS Boolean coercion.
  //       example 1: not_([])
  //       returns 1: true
  //       example 2: not_(NaN)
  //       returns 2: false

  return pythonNot(a)
}

Improve this function

Locutus is a community effort following The McDonald's Theory: we ship first iterations, hoping others will improve them. If you see something that could be better, we'd love your contribution.

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Help us add more

Got a rainy Sunday afternoon and a taste for a porting puzzle?

• Get inspiration from the Python 3 standard library string page.
• Click "New file" in the appropriate folder on GitHub. This will fork the project to your account, directly add the file to it, and send a Pull Request to us.

We will then review it. If it's useful to the project and in line with our contributing guidelines your work will become part of Locutus and you'll be automatically credited in the authors section accordingly.

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