First FastAPI application - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to import FastAPI from the correct package.

FastAPI

from [1] import FastAPI

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

Adjango

Bflask

Cfastapi

Drequests

Attempts:

3 left

💡 Hint

Common Mistakes

Importing FastAPI from Flask or Django.

Trying to import from requests.

You import FastAPI from the fastapi package to create your app.

2fill in blank

medium

Complete the code to create a FastAPI app instance.

FastAPI

app = [1]()

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

AFlask

BRequest

CDjango

DFastAPI

Attempts:

3 left

💡 Hint

Common Mistakes

Using Flask() instead of FastAPI().

Trying to instantiate Request.

You create an app by calling FastAPI().

3fill in blank

hard

Fix the error in the route decorator to define a GET endpoint at root path.

FastAPI

@app.[1]("/")
def read_root():
    return {"Hello": "World"}

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

Adelete

Bget

Cpost

Dput

Attempts:

3 left

💡 Hint

Common Mistakes

Using @app.post instead of @app.get for reading data.

Using wrong HTTP method decorators.

The route decorator for a GET request is @app.get("/").

4fill in blank

hard

Fill both blanks to define a POST endpoint at path '/items' that accepts a parameter named 'item_id'.

FastAPI

@app.[1]("/items/{item_id}")
async def create_item([2]: int):
    return {"item_id": item_id}

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

Apost

Bitem_id

Cget

Did

Attempts:

3 left

💡 Hint

Common Mistakes

Using @app.get instead of @app.post.

Mismatching parameter name and path variable.

The POST decorator is @app.post and the function parameter must match the path variable name item_id.

5fill in blank

hard

Fill all three blanks to run the FastAPI app with uvicorn on host '127.0.0.1' and port 8000.

FastAPI

import uvicorn

if __name__ == "__main__":
    uvicorn.run(app, host=[1], port=[2], log_level=[3])

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

A"0.0.0.0"

B8000

C"info"

D"127.0.0.1"

Attempts:

3 left

💡 Hint

Common Mistakes

Using host 0.0.0.0 which exposes to all networks.

Using wrong port number.

Using incorrect log level string.

To run locally, use host "127.0.0.1", port 8000, and log level "info" for standard output.

Practice

1. What does the @app.get("/") decorator do in a FastAPI application?

easy

A. It starts the FastAPI server automatically.

B. It imports the FastAPI library into the project.

C. It defines a route that responds to HTTP GET requests at the root URL.

D. It creates a database connection for the app.

Solution

1. Step 1: Understand the decorator role

   The @app.get("/") decorator tells FastAPI to listen for GET requests at the root URL path.

2. Step 2: Connect decorator to route handling

   When a user visits the root URL with a GET request, the function below this decorator runs and returns a response.

3. Final Answer:

   It defines a route that responds to HTTP GET requests at the root URL. -> Option C

4. Quick Check:

   Route decorator = defines GET route [OK]

Hint: Decorators like @app.get define routes for HTTP GET requests [OK]

Common Mistakes:

• Thinking @app.get starts the server
• Confusing route decorators with imports
• Assuming it creates database connections

2. Which of the following is the correct way to create a FastAPI app instance?

easy

A. app = FastAPI.create()

B. app = FastAPI()

C. app = FastAPI

D. app = fastapi()

Solution

1. Step 1: Recall FastAPI app creation syntax

   The FastAPI app is created by calling the FastAPI class with parentheses: FastAPI().

2. Step 2: Check each option for correctness

   app = FastAPI() correctly calls FastAPI(). app = fastapi() uses lowercase which is incorrect. app = FastAPI misses parentheses, so it is a class reference, not an instance. app = FastAPI.create() uses a non-existent method.

3. Final Answer:

   app = FastAPI() -> Option B

4. Quick Check:

   FastAPI instance = FastAPI() [OK]

Hint: Create app with FastAPI() including parentheses [OK]

Common Mistakes:

• Omitting parentheses when creating app
• Using lowercase 'fastapi' instead of 'FastAPI'
• Trying to call a non-existent create() method

3. Given this FastAPI code snippet, what will be the JSON response when accessing /hello?

from fastapi import FastAPI
app = FastAPI()

@app.get("/hello")
def say_hello():
    return {"message": "Hello, FastAPI!"}

medium

A. {"message": "Hello, FastAPI!"}

B. "Hello, FastAPI!"

C. {"say_hello": "Hello, FastAPI!"}

D. 404 Not Found error

Solution

1. Step 1: Identify route and return value

   The route /hello is defined with a GET method. The function returns a dictionary with key "message" and value "Hello, FastAPI!".

2. Step 2: Understand FastAPI response format

   FastAPI automatically converts returned dictionaries to JSON responses. So the response will be JSON with the same key-value pair.

3. Final Answer:

   {"message": "Hello, FastAPI!"} -> Option A

4. Quick Check:

   Returned dict = JSON response [OK]

Hint: Returned dict becomes JSON response automatically [OK]

Common Mistakes:

• Expecting plain string instead of JSON
• Confusing function name as JSON key
• Assuming route does not exist causing 404

4. What is wrong with this FastAPI code?

from fastapi import FastAPI
app = FastAPI()

@app.get("/items")
def read_items():
return {"items": [1, 2, 3]}

medium

A. The import statement is incorrect.

B. The route path should be '/item' not '/items'.

C. FastAPI does not support returning lists in JSON.

D. The function read_items is missing an indentation for the return statement.

Solution

1. Step 1: Check Python syntax indentation

   Python requires the return statement inside the function to be indented. Here, return is not indented, causing a syntax error.

2. Step 2: Verify other parts

   The route path '/items' is valid, returning lists is supported, and the import is correct.

3. Final Answer:

   The function read_items is missing an indentation for the return statement. -> Option D

4. Quick Check:

   Python indentation error = missing indent [OK]

Hint: Indent return inside function to avoid syntax errors [OK]

Common Mistakes:

• Ignoring Python indentation rules
• Thinking route path must be singular
• Believing FastAPI can't return lists

5. You want to create a FastAPI app that returns a greeting with a user name from the URL path, like /greet/Alice. Which code correctly implements this?

hard

A. from fastapi import FastAPI
app = FastAPI()

@app.get("/greet/{name}")
def greet(name: str):
return {"greeting": f"Hello, {name}!"}

B. from fastapi import FastAPI
app = FastAPI()

@app.get("/greet")
def greet(name: str):
return {"greeting": f"Hello, {name}!"}

C. from fastapi import FastAPI
app = FastAPI()

@app.get("/greet/{name}")
def greet():
return {"greeting": "Hello!"}

D. from fastapi import FastAPI
app = FastAPI()

@app.get("/greet/{name}")
def greet(name):
return {"greeting": "Hello, name!"}

Solution

1. Step 1: Use path parameter in route

   The route must include {name} in the path to capture the user name from the URL.

2. Step 2: Define function with typed parameter and return greeting

   The function should accept name: str and return a dictionary with a greeting using an f-string to insert the name.

3. Step 3: Check other options for errors

   from fastapi import FastAPI app = FastAPI() @app.get("/greet") def greet(name: str): return {"greeting": f"Hello, {name}!"} misses the path parameter in the route. from fastapi import FastAPI app = FastAPI() @app.get("/greet/{name}") def greet(): return {"greeting": "Hello!"} does not accept the name parameter. from fastapi import FastAPI app = FastAPI() @app.get("/greet/{name}") def greet(name): return {"greeting": "Hello, name!"} does not use f-string, so it returns the literal text "name".

4. Final Answer:

   Uses path parameter and returns personalized greeting. -> Option A

5. Quick Check:

   Path param + f-string = personalized greeting [OK]

Hint: Use {param} in route and f-string to insert it in response [OK]

Common Mistakes:

• Not including path parameter in route string
• Forgetting to type the function parameter
• Returning literal string instead of formatted string