Serving static files in FastAPI - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the purpose of serving static files in a FastAPI application?

Serving static files allows your FastAPI app to deliver files like images, CSS, and JavaScript directly to the browser, making your web pages look and behave properly.

beginner

How do you mount a directory to serve static files in FastAPI?

Use the `app.mount()` method with `StaticFiles(directory='path')` to tell FastAPI where your static files live and under which URL path they should be available.

beginner

Which FastAPI import is required to serve static files?

You need to import `StaticFiles` from `fastapi.staticfiles` to serve static files.

beginner

What URL path is commonly used to serve static files in FastAPI?

A common URL path is `/static`, so files inside your static folder are accessed like `/static/filename.ext`.

beginner

What happens if you try to access a static file that does not exist in FastAPI?

FastAPI will return a 404 Not Found error because the file is missing.

Which FastAPI class is used to serve static files?

A StaticFiles

B FileResponse

C HTMLResponse

D FileServer

StaticFiles is the class designed to serve static files like images, CSS, and JS.

How do you tell FastAPI where your static files are stored?

A Using app.mount() with StaticFiles(directory='path')

B Using app.include_router()

C Using app.add_middleware()

D Using app.static_path()

app.mount() with StaticFiles(directory='path') mounts the static folder to a URL path.

If you mount static files at '/static', how do you access 'logo.png' inside that folder?

A /files/logo.png

B /logo.png

C /static/logo.png

D /assets/logo.png

Files are accessed by combining the mount path and the file name.

What HTTP status code does FastAPI return if a static file is missing?

A 500 Internal Server Error

B 200 OK

C 403 Forbidden

D 404 Not Found

A missing file results in a 404 Not Found error.

Which import is necessary to serve static files in FastAPI?

A from fastapi.responses import StaticFiles

B from fastapi.staticfiles import StaticFiles

C from fastapi.middleware import StaticFiles

D from fastapi.static import StaticFiles

StaticFiles is imported from fastapi.staticfiles.

Explain how to serve static files in a FastAPI app step-by-step.

Think about telling FastAPI where your files are and how users get them.

Describe what happens when a user requests a static file in FastAPI.

Consider the journey from request to response.

Practice

1. What is the main purpose of using StaticFiles in a FastAPI application?

easy

A. To serve images, CSS, and JavaScript files to users

B. To handle database connections

C. To create API endpoints for data processing

D. To manage user authentication

Solution

1. Step 1: Understand StaticFiles role

   StaticFiles is used to serve static content like images, CSS, and JavaScript files in FastAPI.

2. Step 2: Compare with other options

   Database handling, API endpoints, and authentication are unrelated to static file serving.

3. Final Answer:

   To serve images, CSS, and JavaScript files to users -> Option A

4. Quick Check:

   StaticFiles serves static content = A [OK]

Hint: StaticFiles always serves static content like images or CSS [OK]

Common Mistakes:

• Confusing StaticFiles with API route handlers
• Thinking StaticFiles manages databases
• Assuming StaticFiles handles user login

2. Which of the following is the correct way to mount a static folder named 'assets' at URL path '/static' in FastAPI?

easy

A. app.route('/static').static_files('assets')

B. app.mount('/static', StaticFiles(directory='assets'), name='static')

C. app.add_static('/static', 'assets')

D. app.static('/assets', directory='/static')

Solution

1. Step 1: Recall FastAPI static file syntax

   The correct method is app.mount(path, StaticFiles(directory=folder), name=alias).

2. Step 2: Match syntax with options

   app.mount('/static', StaticFiles(directory='assets'), name='static') matches this pattern exactly, mounting 'assets' at '/static'. Others use invalid methods.

3. Final Answer:

   app.mount('/static', StaticFiles(directory='assets'), name='static') -> Option B

4. Quick Check:

   Use app.mount with StaticFiles = D [OK]

Hint: Use app.mount with StaticFiles and directory parameter [OK]

Common Mistakes:

• Using app.static or app.add_static which don't exist
• Swapping URL path and directory names
• Omitting the name parameter

3. Given this FastAPI code snippet:

from fastapi import FastAPI
from fastapi.staticfiles import StaticFiles

app = FastAPI()
app.mount('/files', StaticFiles(directory='myfiles'), name='files')

What URL path should you visit in a browser to access a file named image.png inside the myfiles folder?

medium

A. /myfiles/image.png

B. /static/image.png

C. /files/image.png

D. /image.png

Solution

1. Step 1: Identify mount path and directory

   The static files are mounted at URL path '/files' serving from folder 'myfiles'.

2. Step 2: Construct URL for file

   To access 'image.png' inside 'myfiles', visit '/files/image.png' in the browser.

3. Final Answer:

   /files/image.png -> Option C

4. Quick Check:

   URL path matches mount path + filename = B [OK]

Hint: URL path equals mount path plus file name [OK]

Common Mistakes:

• Using directory name as URL path instead of mount path
• Assuming '/static' is default path
• Trying to access file without mount prefix

4. What is wrong with this FastAPI code for serving static files?

from fastapi import FastAPI
from fastapi.staticfiles import StaticFiles

app = FastAPI()
app.mount('/static', StaticFiles('static'), name='static')

medium

A. The URL path '/static' is invalid

B. app.mount cannot be used for static files

C. The name parameter is missing

D. Nothing is wrong with this code

Solution

1. Step 1: Check StaticFiles usage

   StaticFiles('static') is correct because the first positional argument binds to the directory parameter.

2. Step 2: Validate other parts

   app.mount is correct for static files, name parameter is present, and '/static' is a valid URL path.

3. Final Answer:

   Nothing is wrong with this code -> Option D

4. Quick Check:

   StaticFiles('static') correctly sets directory='static' = A [OK]

Hint: StaticFiles accepts positional argument for directory [OK]

Common Mistakes:

• Thinking StaticFiles requires named directory parameter
• Thinking app.mount can't serve static files
• Confusing URL path with directory name

5. You want to serve two different static folders in your FastAPI app: 'images' at '/img' and 'scripts' at '/js'. Which code correctly mounts both folders?

hard

A. app.mount('/img', StaticFiles(directory='images'), name='images')
app.mount('/js', StaticFiles(directory='scripts'), name='scripts')

B. app.mount('/images', StaticFiles(directory='img'), name='img')
app.mount('/scripts', StaticFiles(directory='js'), name='js')

C. app.static('/img', 'images')
app.static('/js', 'scripts')

D. app.add_static('/img', 'images')
app.add_static('/js', 'scripts')

Solution

1. Step 1: Verify correct mount syntax

   Use app.mount(path, StaticFiles(directory=folder), name=alias) for each static folder.

2. Step 2: Match folders and paths

   app.mount('/img', StaticFiles(directory='images'), name='images') app.mount('/js', StaticFiles(directory='scripts'), name='scripts') correctly mounts 'images' at '/img' and 'scripts' at '/js'. Options A, B, D use wrong paths or invalid methods.

3. Final Answer:

   app.mount('/img', StaticFiles(directory='images'), name='images') app.mount('/js', StaticFiles(directory='scripts'), name='scripts') -> Option A

4. Quick Check:

   Mount each folder with app.mount and StaticFiles = C [OK]

Hint: Mount each folder separately with app.mount and StaticFiles [OK]

Common Mistakes:

• Swapping folder names and URL paths
• Using non-existent app.static or app.add_static methods
• Missing name parameter in mount