File responses in FastAPI - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to import the correct class for sending a file response in FastAPI.

FastAPI

from fastapi import FastAPI
from fastapi.responses import [1]

app = FastAPI()

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

AHTMLResponse

BJSONResponse

CRedirectResponse

DFileResponse

Attempts:

3 left

💡 Hint

Common Mistakes

Importing JSONResponse or HTMLResponse instead of FileResponse.

Forgetting to import any response class.

The FileResponse class is used in FastAPI to send files as responses.

2fill in blank

medium

Complete the code to return a file named 'example.txt' from the '/download' route.

FastAPI

from fastapi import FastAPI
from fastapi.responses import FileResponse

app = FastAPI()

@app.get('/download')
async def download_file():
    return [1]('example.txt')

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

AJSONResponse

BHTMLResponse

CFileResponse

DRedirectResponse

Attempts:

3 left

💡 Hint

Common Mistakes

Returning JSONResponse or HTMLResponse instead of FileResponse.

Forgetting to specify the filename.

Use FileResponse to send the file 'example.txt' as a response.

3fill in blank

hard

Fix the error in the code to correctly send a file with a custom filename 'report.pdf' in the response.

FastAPI

from fastapi import FastAPI
from fastapi.responses import FileResponse

app = FastAPI()

@app.get('/report')
async def get_report():
    return FileResponse('files/report.pdf', [1]='report.pdf')

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

Afile

Bfilename

Cname

Dfile_name

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'file_name' or 'name' instead of 'filename'.

Passing the filename as a positional argument.

The correct parameter to set the download filename in FileResponse is filename.

4fill in blank

hard

Fill both blanks to send a file with media type 'application/pdf' and enable HTTP caching.

FastAPI

from fastapi import FastAPI
from fastapi.responses import FileResponse

app = FastAPI()

@app.get('/pdf')
async def get_pdf():
    return FileResponse('docs/sample.pdf', media_type=[1], [2]='max-age=3600')

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

A'application/pdf'

Bbackground

Ccache_control

Duse_cache

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong media type strings.

Using incorrect parameter names for caching.

The media_type should be 'application/pdf' for PDF files, and cache_control enables HTTP caching.

5fill in blank

hard

Fill all three blanks to send a file with custom filename, media type, and set background task to delete the file after sending.

FastAPI

from fastapi import FastAPI
from fastapi.responses import FileResponse
from fastapi.background import BackgroundTask
import os

app = FastAPI()

def remove_file(path: str):
    os.remove(path)

@app.get('/tempfile')
async def send_temp_file():
    path = 'temp/data.txt'
    return FileResponse(path, filename=[1], media_type=[2], background=BackgroundTask([3], path))

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

A'data.txt'

B'text/plain'

Cremove_file(path)

Dremove_file

Attempts:

3 left

💡 Hint

Common Mistakes

Calling remove_file(path) instead of passing remove_file.

Using wrong media type strings.

Not setting the filename parameter.

Set filename to 'data.txt', media_type to 'text/plain', and pass the function remove_file (without calling it) to BackgroundTask to delete the file after sending.

Practice

1. What is the main purpose of FileResponse in FastAPI?

easy

A. To send files from the server to the client

B. To upload files from the client to the server

C. To delete files on the server

D. To read file contents as text

Solution

1. Step 1: Understand the role of FileResponse

   FileResponse is designed to send files from the server to the client in FastAPI.

2. Step 2: Differentiate from other file operations

   Uploading or deleting files are handled differently; FileResponse specifically sends files.

3. Final Answer:

   To send files from the server to the client -> Option A

4. Quick Check:

   FileResponse sends files [OK]

Hint: FileResponse is for sending files to users [OK]

Common Mistakes:

• Confusing FileResponse with file upload handling
• Thinking FileResponse reads file content as text
• Assuming FileResponse deletes files

2. Which of the following is the correct way to import FileResponse in FastAPI?

easy

A. from fastapi.responses import file_response

B. from fastapi import FileResponse

C. import FileResponse from fastapi.responses

D. from fastapi.responses import FileResponse

Solution

1. Step 1: Recall correct import syntax

   FastAPI's FileResponse is imported from fastapi.responses using Python's standard import syntax.

2. Step 2: Check each option's correctness

   from fastapi.responses import FileResponse uses correct syntax and casing. from fastapi import FileResponse misses the submodule. import FileResponse from fastapi.responses uses wrong syntax. from fastapi.responses import file_response uses wrong casing.

3. Final Answer:

   from fastapi.responses import FileResponse -> Option D

4. Quick Check:

   Correct import is from fastapi.responses [OK]

Hint: Import FileResponse from fastapi.responses [OK]

Common Mistakes:

• Using wrong import syntax like 'import X from Y'
• Importing directly from fastapi without .responses
• Wrong casing like file_response instead of FileResponse

3. What will the following FastAPI endpoint return?

from fastapi import FastAPI
from fastapi.responses import FileResponse

app = FastAPI()

@app.get('/download')
async def download_file():
    return FileResponse('example.pdf', media_type='application/pdf', filename='report.pdf')

medium

A. Returns JSON with file path 'example.pdf'

B. Sends the file 'example.pdf' with download name 'report.pdf' and PDF media type

C. Raises an error because filename cannot be set

D. Sends 'report.pdf' file ignoring 'example.pdf'

Solution

1. Step 1: Analyze FileResponse parameters

   The first argument is the file path to send ('example.pdf'). The media_type sets the content type to PDF. The filename sets the suggested download name.

2. Step 2: Understand the endpoint behavior

   When called, the endpoint sends the file 'example.pdf' with content type 'application/pdf' and suggests the name 'report.pdf' for download.

3. Final Answer:

   Sends the file 'example.pdf' with download name 'report.pdf' and PDF media type -> Option B

4. Quick Check:

   FileResponse sends file with given path and filename [OK]

Hint: FileResponse(path, media_type, filename) sends file with custom name [OK]

Common Mistakes:

• Thinking filename argument changes the file read
• Expecting JSON response instead of file
• Assuming filename cannot be set

4. Identify the error in this FastAPI endpoint that tries to send a file:

from fastapi import FastAPI
from fastapi.responses import FileResponse

app = FastAPI()

@app.get('/file')
async def get_file():
    return FileResponse(filepath='data.txt', media_type='text/plain')

medium

A. FileResponse does not accept a 'filepath' keyword argument

B. The media_type 'text/plain' is invalid

C. FileResponse requires a filename argument

D. The endpoint must be synchronous, not async

Solution

1. Step 1: Check FileResponse constructor parameters

   FileResponse expects the file path as the first positional argument, not as a 'filepath' keyword argument.

2. Step 2: Identify the error cause

   Passing 'filepath=' causes a TypeError because FileResponse does not have a 'filepath' parameter.

3. Final Answer:

   FileResponse does not accept a 'filepath' keyword argument -> Option A

4. Quick Check:

   FileResponse needs file path as first argument, no 'filepath=' [OK]

Hint: FileResponse takes file path as first argument, no 'filepath=' keyword [OK]

Common Mistakes:

• Using 'filepath=' keyword instead of positional argument
• Thinking filename is mandatory
• Believing async is not allowed for endpoints

5. You want to create a FastAPI endpoint that sends a file only if it exists, otherwise returns a 404 error. Which code snippet correctly implements this behavior?

hard

A. from fastapi import FastAPI
from fastapi.responses import FileResponse

app = FastAPI()

@app.get('/download')
async def download():
return FileResponse('file.txt')

B. from fastapi import FastAPI
from fastapi.responses import FileResponse

app = FastAPI()

@app.get('/download')
async def download():
try:
return FileResponse('file.txt')
except FileNotFoundError:
return {'error': 'File missing'}

C. from fastapi import FastAPI, HTTPException
from fastapi.responses import FileResponse
import os

app = FastAPI()

@app.get('/download')
async def download():
if os.path.exists('file.txt'):
return FileResponse('file.txt')
else:
raise HTTPException(status_code=404, detail='File not found')

D. from fastapi import FastAPI
from fastapi.responses import FileResponse

app = FastAPI()

@app.get('/download')
async def download():
if 'file.txt' in os.listdir('.'):
return FileResponse('file.txt')
else:
return {'error': 'File not found'}

Solution

1. Step 1: Check file existence properly

   Using os.path.exists('file.txt') correctly checks if the file exists before sending.

2. Step 2: Return appropriate response on missing file

   Raising HTTPException with 404 status is the proper way to signal file not found in FastAPI.

3. Final Answer:

   Code snippet B correctly checks file existence and raises 404 if missing -> Option C

4. Quick Check:

   Check file with os.path.exists + raise HTTPException [OK]

Hint: Check file with os.path.exists, raise HTTPException 404 if missing [OK]

Common Mistakes:

• Not checking file existence before sending
• Returning JSON error instead of raising HTTPException
• Using try-except without proper exception handling