A dynamic variable file

Part 6 · Custom Libraries with Python›19b · Variable filesLibraries · dynamic variables

Chapter lab: Variable filesch19b-variable-files.zip · 4 KB

This lesson continues in the same lab as the lesson before it. If you don’t have it yet, download it here.

Download ch19b-variable-files.zip

Or fetch and unpack it from a terminal in VS Code:

bash / zsh

curl -fsSLO https://manykarim.github.io/robotframework-essentials-web/labs/ch19b-variable-files.zip && unzip -q ch19b-variable-files.zip && rm ch19b-variable-files.zip

PowerShell

Invoke-WebRequest https://manykarim.github.io/robotframework-essentials-web/labs/ch19b-variable-files.zip -OutFile ch19b-variable-files.zip; Expand-Archive ch19b-variable-files.zip -DestinationPath .; Remove-Item ch19b-variable-files.zip

Open the folder in VS Code with code rfe-ch19b-variable-files (or File → Open Folder…) and accept the recommended RobotCode and Python extensions. Then set it up:

uv sync

bash / zsh

python3 -m venv .venv
source .venv/bin/activate
pip install -r requirements.txt

PowerShell

python -m venv .venv
.venv\Scripts\Activate.ps1
pip install -r requirements.txt

Keep the environment active in every terminal where you run lesson commands.

poetry install --no-root

Python 3.13 or newer is required; uv installs it when it is missing.

Open in browserNo setup? Try the lab right here: its files, an editor and a terminal, running in your browser.

What's inside

• Directoryrfe-ch19b-variable-files/

  • Directory.vscode/

    • extensions.json
  • Directorychecks/

    • smoke.robot
  • Directorylibraries/

    • README.md
  • Directoryvariables/

    • README.md
  • .gitignore
  • .python-version
  • LAB.md
  • pyproject.toml
  • README.md
  • requirements.txt
  • uv.lock

A static variable file is fixed at import time. A dynamic one computes its variables when imported — from an argument, the environment, or a lookup — so a single file can serve many situations.

The mechanism: instead of module-level names, define a function get_variables() that returns a dictionary. Its keys become the variables. Give it a parameter and pass a value on the Variables import, and one file can supply, say, staging or production settings on demand.

Task 1 — Write a get_variables file

Edit

Goal: create variables/env_config.py with get_variables(env="staging") that returns a dictionary of settings for the chosen environment (API_URL, RETRIES), with staging and prod options.

Here is the same shape over different data — subscription tiers. Adapt it to environments.

Worked example — adapt it, don’t copy it

def get_variables(tier="basic"):
    tiers = {
        "basic": {"MAX_ITEMS": 10, "SUPPORT": "email"},
        "pro": {"MAX_ITEMS": 100, "SUPPORT": "phone"},
    }
    return tiers[tier]

Done when

variables/env_config.py defines a get_variables function.

Hint 1

Return a dict from get_variables — its keys become variables: def get_variables(env="staging"): returning a per-environment dictionary.

Hint 2

Key the settings by environment and select with the argument: envs = {"staging": {...}, "prod": {...}} then return envs[env].

Solution

def get_variables(env="staging"):
    envs = {
        "staging": {"API_URL": "http://staging.local", "RETRIES": 3},
        "prod": {"API_URL": "http://prod.local", "RETRIES": 5},
    }
    return envs[env]

Task 2 — Import it with an argument and run it green

Run

Create checks/env_config.robot. Pass the environment as an argument to the Variables import — the file computes the matching settings:

*** Settings ***
Variables    ../variables/env_config.py    prod

*** Test Cases ***
Environment Values Resolve
    Should Be Equal    ${API_URL}    http://prod.local
    Should Be Equal As Integers    ${RETRIES}    5

Run it:

uv run robot checks/env_config.robot

robot checks/env_config.robot

poetry run robot checks/env_config.robot

Done when

the test Environment Values Resolve passes.

Check your understanding

Quick recall. Your first answer stays in this browser; the quiz never blocks your progress.

1. A dynamic variable file provides its variables via…

   module-level namesa get_variables() function returning a dicta class
   Show the answer

   Answer: a get_variables() function returning a dict — get_variables() returns a dictionary whose keys become variables; it can compute them from an argument or the environment.

2. How can one variable file serve many environments?

   not possiblegive get_variables a parameter passed on the Variables importone file per environment only
   Show the answer

   Answer: give get_variables a parameter passed on the Variables import — Variables env_config.py prod passes prod to get_variables(env), which returns that environment's settings.

Key terms

get_variablesconcept

Function returning a dict of variables, computed at import time.

parameterized variable fileconcept

Pass an argument on the Variables import to select values (e.g. an environment).

All terms in the glossary →