Environment variable management in FastAPI - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to load environment variables using Pydantic BaseSettings.

FastAPI

from pydantic import BaseSettings

class Settings(BaseSettings):
    app_name: str

settings = Settings()
print(settings.[1])

Drag options to blanks, or click blank then click option'

Aenv_var

Bload_env

Capp_name

Dconfig

Attempts:

3 left

💡 Hint

Common Mistakes

Trying to call a method that does not exist on the settings instance.

Using a wrong attribute name that is not defined in the Settings class.

The app_name attribute is accessed from the settings instance to get the environment variable value.

2fill in blank

medium

Complete the code to specify a custom environment file for Pydantic BaseSettings.

FastAPI

from pydantic import BaseSettings

class Settings(BaseSettings):
    debug: bool

    class Config:
        env_file = [1]

settings = Settings()
print(settings.debug)

Drag options to blanks, or click blank then click option'

A"variables.txt"

B"config.json"

C"settings.yaml"

D".env"

Attempts:

3 left

💡 Hint

Common Mistakes

Using a file format that Pydantic does not parse by default.

Forgetting to include quotes around the filename string.

The env_file attribute in the Config class tells Pydantic to load environment variables from a file named .env.

3fill in blank

hard

Fix the error in the code to correctly read an integer environment variable.

FastAPI

from pydantic import BaseSettings

class Settings(BaseSettings):
    port: int

settings = Settings()
print(settings.[1])

Drag options to blanks, or click blank then click option'

Aport

BPORT

Cport_number

Dget_port

Attempts:

3 left

💡 Hint

Common Mistakes

Using uppercase or different names that do not match the attribute.

Trying to call a method instead of accessing the attribute.

The attribute name port must match the class attribute to access the integer environment variable correctly.

4fill in blank

hard

Fill both blanks to create a Pydantic Settings class that reads a string and a boolean from environment variables.

FastAPI

from pydantic import BaseSettings

class Settings(BaseSettings):
    [1]: str
    [2]: bool

settings = Settings()
print(settings.api_key, settings.debug_mode)

Drag options to blanks, or click blank then click option'

Aapi_key

Bdebug

Cdebug_mode

Dapi_secret

Attempts:

3 left

💡 Hint

Common Mistakes

Using attribute names that do not match the environment variables.

Mixing up the types or names for the variables.

The class defines api_key as a string and debug_mode as a boolean to read those environment variables.

5fill in blank

hard

Fill all three blanks to create a Settings class that reads a host string, a port integer, and a debug boolean from environment variables.

FastAPI

from pydantic import BaseSettings

class Settings(BaseSettings):
    [1]: str
    [2]: int
    [3]: bool

settings = Settings()
print(settings.host, settings.port, settings.debug)

Drag options to blanks, or click blank then click option'

Ahost

Bport

Cdebug

Dhostname

Attempts:

3 left

💡 Hint

Common Mistakes

Using inconsistent or incorrect attribute names.

Not matching the type annotations to the variable types.

The class attributes host, port, and debug correspond to environment variables for host, port, and debug mode.

Practice

1. What is the main reason to use environment variables in a FastAPI project?

easy

A. To keep sensitive information like API keys out of the code

B. To make the code run faster

C. To store user data permanently

D. To create new API endpoints automatically

Solution

1. Step 1: Understand environment variables purpose

   Environment variables are used to keep sensitive data like passwords or API keys separate from the code to improve security.

2. Step 2: Identify the correct reason in FastAPI context

   FastAPI uses environment variables to avoid hardcoding secrets, which helps keep them safe and flexible.

3. Final Answer:

   To keep sensitive information like API keys out of the code -> Option A

4. Quick Check:

   Environment variables = keep secrets safe [OK]

Hint: Environment variables store secrets, not speed or data [OK]

Common Mistakes:

• Thinking environment variables speed up code
• Confusing environment variables with database storage
• Assuming environment variables create API routes

2. Which of the following is the correct way to get an environment variable named API_KEY using Python's os module in FastAPI?

easy

A. api_key = os.get('API_KEY')

B. api_key = os.getenv('API_KEY')

C. api_key = os.environ.get('API_KEY')()

D. api_key = os.getenv(API_KEY)

Solution

1. Step 1: Recall correct os module function

   The correct function to get environment variables is os.getenv('VAR_NAME').

2. Step 2: Check syntax correctness

   api_key = os.getenv('API_KEY') uses os.getenv('API_KEY') correctly with quotes around the variable name and no extra parentheses.

3. Final Answer:

   api_key = os.getenv('API_KEY') -> Option B

4. Quick Check:

   Use os.getenv('VAR') to get environment variables [OK]

Hint: Use os.getenv('VAR_NAME') with quotes [OK]

Common Mistakes:

• Using os.get instead of os.getenv
• Calling os.environ.get with extra parentheses
• Not quoting the environment variable name

3. Given this FastAPI code snippet using Pydantic's BaseSettings:

from pydantic import BaseSettings

class Settings(BaseSettings):
    app_name: str
    debug_mode: bool = False

settings = Settings()

If the environment variable APP_NAME is set to "MyApp" and DEBUG_MODE is not set, what will settings.app_name and settings.debug_mode be?

medium

A. None and None

B. "MyApp" and True

C. None and False

D. "MyApp" and False

Solution

1. Step 1: Understand BaseSettings behavior

   Pydantic BaseSettings reads environment variables matching attribute names in uppercase by default.

2. Step 2: Check provided environment variables and defaults

   APP_NAME is set to "MyApp", so settings.app_name is "MyApp". DEBUG_MODE is not set, so it uses the default False.

3. Final Answer:

   "MyApp" and False -> Option D

4. Quick Check:

   Env var set = value, missing uses default [OK]

Hint: Unset vars use default values in BaseSettings [OK]

Common Mistakes:

• Assuming missing env vars become True
• Thinking unset vars become None instead of default
• Confusing attribute names with env var names

4. What is wrong with this FastAPI environment variable usage code?

import os

API_KEY = os.getenv('API_KEY')
print(f"API key is {API_KEY.upper()}")

Assuming API_KEY is not set in the environment.

medium

A. It will raise an AttributeError because API_KEY is None

B. It will print 'API key is ' with empty string

C. It will raise a SyntaxError

D. It will print the string 'None'

Solution

1. Step 1: Check os.getenv behavior when var missing

   os.getenv returns None if the environment variable is not set and no default is given.

2. Step 2: Understand what happens calling upper() on None

   Calling None.upper() raises an AttributeError because NoneType has no method upper().

3. Final Answer:

   It will raise an AttributeError because API_KEY is None -> Option A

4. Quick Check:

   None.upper() causes AttributeError [OK]

Hint: Check for None before calling string methods [OK]

Common Mistakes:

• Assuming os.getenv returns empty string if missing
• Expecting no error when calling upper() on None
• Confusing AttributeError with SyntaxError

5. You want to manage environment variables in FastAPI using Pydantic's BaseSettings and ensure a default port of 8000 if PORT is not set. Which code snippet correctly achieves this?

hard

A. class Settings(BaseSettings):
port: int

settings = Settings(port=8000)

B. class Settings(BaseSettings):
port: int

settings = Settings() # default 8000 if missing

C. class Settings(BaseSettings):
port: int = 8000

settings = Settings()

D. class Settings(BaseSettings):
port: str = '8000'

settings = Settings()

Solution

1. Step 1: Define default value in BaseSettings attribute

   Setting port: int = 8000 provides a default if the environment variable PORT is missing.

2. Step 2: Instantiate Settings without arguments

   Calling Settings() reads environment variables or uses defaults if missing, so port will be 8000 if PORT is unset.

3. Final Answer:

   class Settings(BaseSettings): port: int = 8000 settings = Settings() -> Option C

4. Quick Check:

   Default values in BaseSettings = default used if env var missing [OK]

Hint: Set default in class attribute for fallback [OK]

Common Mistakes:

• Not providing default and expecting fallback
• Passing default in constructor instead of attribute
• Using string type for port instead of int