# 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).

# Variables de Entorno

/// 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).

$ 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
```

</div>

////

//// tab | Windows PowerShell

<div class="termy">

এনভায়রনমেন্ট ভেরিয়েবল ব্যবহার করে **এপ্লিকেশন সেটিংস** হ্যান্ডেল করা নিয়ে আরো বিস্তারিত জানা যাবে [Advanced User Guide - Settings and Environment Variables](./advanced/settings.md){.internal-link target=_blank}.

## `PATH` এনভায়রনমেন্ট ভেরিয়েবল

# Biến môi trường (Environment Variables)

/// tip

Nếu bạn đã biết về "biến môi trường" và cách sử dụng chúng, bạn có thể bỏ qua phần này.

///

Một biến môi trường (còn được gọi là "**env var**") là một biến mà tồn tại **bên ngoài** đoạn mã Python, ở trong **hệ điều hành**, và có thể được đọc bởi đoạn mã Python của bạn (hoặc bởi các chương trình khác).

Mohammad <******@****.***> 1753435623 +0330

/// tip | Consejo

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

///

## Tipos y validación

Estas variables de entorno solo pueden manejar strings de texto, ya que son externas a Python y tienen que ser compatibles con otros programas y el resto del sistema (e incluso con diferentes sistemas operativos, como Linux, Windows, macOS).

# 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