3.3Dictionaries and Objects

Dictionaries (Python) and objects (JavaScript) are the native format for JSON data, API responses, and configuration. You will work with them constantly.

Python Dictionaries

# API response handling
user = {"email": "test@example.com", "role": "admin", "active": True}
assert response.json()["email"] == user["email"]

# Safely access nested data
config = {
    "environments": {
        "staging": {"url": "https://staging.example.com", "timeout": 30},
        "production": {"url": "https://example.com", "timeout": 10}
    }
}
staging_url = config.get("environments", {}).get("staging", {}).get("url")
assert staging_url == "https://staging.example.com"

# Dictionary comparison for response validation
expected = {"id": 1, "name": "Alice", "role": "admin"}
actual = response.json()
# Check expected is a subset of actual (actual may have extra fields)
for key, value in expected.items():
    assert actual[key] == value, f"Mismatch on {key}: expected {value}, got {actual[key]}"

# Merge dictionaries (Python 3.9+)
default_headers = {"Content-Type": "application/json"}
auth_headers = {"Authorization": "Bearer token123"}
headers = default_headers | auth_headers

JavaScript/TypeScript Objects

// Destructuring API responses
const { id, name, email } = response.data;
expect(id).toBeDefined();
expect(name).toBe("Alice");

// Spread operator for merging
const defaultHeaders = { "Content-Type": "application/json" };
const authHeaders = { Authorization: "Bearer token123" };
const headers = { ...defaultHeaders, ...authHeaders };

// Optional chaining for safe access
const stagingUrl = config?.environments?.staging?.url;
expect(stagingUrl).toBe("https://staging.example.com");

// Check object shape
expect(Object.keys(user)).toEqual(expect.arrayContaining(["id", "name", "email"]));