# Variables de Entorno { #environment-variables }

/// tip | Consejo

Si ya sabes qué son las "variables de entorno" y cómo usarlas, siéntete libre de saltarte esto.

///

Una variable de entorno (también conocida como "**env var**") es una variable que vive **fuera** del código de Python, en el **sistema operativo**, y podría ser leída por tu código de Python (o por otros programas también).

# Environment Variables { #environment-variables }

/// tip

If you already know what "environment variables" are and how to use them, feel free to skip this.

///

An environment variable (also known as "**env var**") is a variable that lives **outside** of the Python code, in the **operating system**, and could be read by your Python code (or by other programs as well).

# Переменные окружения { #environment-variables }

/// tip | Совет

Если вы уже знаете, что такое «переменные окружения» и как их использовать, можете пропустить это.

///

Переменная окружения (также известная как «**env var**») - это переменная, которая живет **вне** кода Python, в **операционной системе**, и может быть прочитана вашим кодом Python (или другими программами).

# Variáveis de Ambiente { #environment-variables }

/// tip | Dica

Se você já sabe o que são "variáveis de ambiente" e como usá-las, pode pular esta seção.

///

Uma variável de ambiente (também conhecida como "**env var**") é uma variável que existe **fora** do código Python, no **sistema operacional**, e pode ser lida pelo seu código Python (ou por outros programas também).

# Umgebungsvariablen { #environment-variables }

/// tip | Tipp

Wenn Sie bereits wissen, was „Umgebungsvariablen“ sind und wie man sie verwendet, können Sie dies überspringen.

///

Eine Umgebungsvariable (auch bekannt als „**env var**“) ist eine Variable, die **außerhalb** des Python-Codes im **Betriebssystem** lebt und von Ihrem Python-Code (oder auch von anderen Programmen) gelesen werden kann.

$ python main.py

// As we didn't set the env var, we get the default value

Hello World from Python

// But if we create an environment variable first
$ export MY_NAME="Wade Wilson"

// And then call the program again
$ python main.py

// Now it can read the environment variable

Hello Wade Wilson from Python
```

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////

//// tab | Windows PowerShell

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/// tip | Consejo

Para entender las variables de entorno, puedes leer [Variables de Entorno](../environment-variables.md){.internal-link target=_blank}.

///

## Tipos y validación { #types-and-validation }

# variables in it, OR may be left empty if the user has already exported the
# relevant variables in their environment. Because of 'set -o allexport' above
# (which is equivalent to "set -a"), every variable in the file is exported
# for other files to use.
#
# Separately, if TFCI is set *and* there are also additional TFCI_ variables

To understand environment variables you can read [Environment Variables](../environment-variables.md){.internal-link target=_blank}.

///

## Types and validation { #types-and-validation }

These environment variables can only handle text strings, as they are external to Python and have to be compatible with other programs and the rest of the system (and even with different operating systems, as Linux, Windows, macOS).

   *
   * @param formal The type whose type variables or itself is mapped to other type(s). It's almost
   *     always a bug if {@code formal} isn't a type variable and contains no type variable. Make
   *     sure you are passing the two parameters in the right order.
   * @param actual The type that the formal type variable(s) are mapped to. It can be or contain yet