File upload (single file) in FastAPI - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the main FastAPI class used to handle file uploads?

FastAPI uses the <code>UploadFile</code> class to handle file uploads efficiently without loading the entire file into memory.

beginner

How do you declare a single file upload parameter in a FastAPI endpoint?

You declare a parameter with type UploadFile and use File() from fastapi to mark it as a file upload, for example: file: UploadFile = File(...).

intermediate

What method do you use to read the contents of an uploaded file in FastAPI?

You use the read() method on the UploadFile object to get the file content as bytes, e.g., contents = await file.read().

intermediate

Why is UploadFile preferred over bytes for file uploads in FastAPI?

UploadFile streams the file and uses temporary storage, which is more memory efficient for large files compared to loading the entire file as bytes.

intermediate

How do you save an uploaded file to disk in FastAPI?

You open a file in write-binary mode and write the contents read from UploadFile, for example:<br>

with open('filename', 'wb') as f:
    f.write(await file.read())

Which FastAPI import is required to declare a file upload parameter?

A FileHandler from fastapi

B File from fastapi

C FileUpload from fastapi

D UploadFile from starlette

You must import File from fastapi to declare a file upload parameter.

What type should a single file upload parameter have in FastAPI?

A UploadFile

B str

C bytes

D File

The parameter should be typed as UploadFile to handle file uploads efficiently.

How do you access the filename of an uploaded file in FastAPI?

A file.filename

B file.name

C file.file_name

D file.get_name()

The UploadFile object has a filename attribute with the original file name.

Which method reads the entire content of an uploaded file asynchronously?

A file.read()

B file.read_bytes()

C await file.read()

D await file.get()

You must use await file.read() because read() is an async method.

What is a benefit of using UploadFile over bytes for uploads?

A Faster upload speed

B Supports multiple files only

C Automatically compresses files

D Streams file to disk, saving memory

UploadFile streams the file and uses temporary storage, which is more memory efficient.

Explain how to create a FastAPI endpoint that accepts a single file upload and saves it to disk.

Think about the parameter type, reading the file, and saving it.

Describe why using UploadFile is better than bytes for handling file uploads in FastAPI.

Consider memory use and file size.