Welcome back! Today's focus will be on downloading files from an API. Understanding how to retrieve files efficiently not only enhances your technical skills but also broadens your application's capabilities. In this lesson, we'll explore a practical scenario using our To-Do list API, which, in addition to managing tasks, supports handling text files such as notes. These notes can be downloaded or uploaded through the /notes endpoint, allowing functionality for storing supplementary information. For example, users might keep notes about a meeting or important reminders. By understanding how to interact with this endpoint, you can effectively manage notes within your application. By the end of this lesson, you'll know how to request a file from an API, save it locally, and verify its contents.

Let's dive into downloading files with precision and confidence!

GET requests are fundamental for retrieving files from an API. When you send a GET request using requests.get(), your client communicates with the server at a specified URL, asking it to provide the file. The server responds with the file data, if available and permissible, along with an HTTP status code (like 200 OK).

Here's a basic example of downloading a file named welcome.txt from our API at http://localhost:8000/notes. This approach downloads the entire file at once, which is manageable for smaller files.

Python
Copy to clipboard
1import requests
2
3# Base URL for the API
4base_url = "http://localhost:8000"
5
6# Specify the note name to download
7note_name = "welcome.txt"
8
9try:
10    # Send a GET request to download the file
11    response = requests.get(f"{base_url}/notes/{note_name}")
12    
13    # Raise an HTTPError for bad responses (4xx and 5xx status codes)
14    response.raise_for_status()
15    
16    # Save the file locally
17    with open(f"downloaded_{note_name}", "wb") as file:
18        file.write(response.content)
19
20except requests.exceptions.HTTPError as http_err:
21    print(f"HTTP error occurred: {http_err}")
22except requests.exceptions.RequestException as err:
23    print(f"Other error occurred: {err}")

This code sends a GET request and writes the full response content to a local file. This method works well for small files but can strain memory for larger files.

When dealing with large files, downloading them all at once can be inefficient and strain memory. To address this, enable streaming by setting stream=True in requests.get(). This approach watches for HTTP's built-in capabilities to download files in chunks, thus optimizing memory usage and maintaining efficiency.

Below is a detailed code example demonstrating how to download the same file using streaming:

Python
Copy to clipboard
1import requests
2
3# Base URL for the API
4base_url = "http://localhost:8000"
5
6# Specify the note name to download
7note_name = "welcome.txt"
8
9try:
10    # Send a GET request to the API, enabling streaming for large file responses
11    response = requests.get(f"{base_url}/notes/{note_name}", stream=True)
12    
13    # Raise an HTTPError for bad responses (4xx and 5xx status codes)
14    response.raise_for_status()
15    
16    # Define the filename for storing the downloaded content
17    file_name = f"downloaded_{note_name}"
18    
19    # Open the local file in binary write mode
20    with open(file_name, "wb") as file:
21        # Iterate over the response data in chunks
22        for chunk in response.iter_content(chunk_size=1024):
23            file.write(chunk)
24
25except requests.exceptions.HTTPError as http_err:
26    # Handle HTTP errors
27    error_message = response.json().get('error', 'Unknown error')
28    print(f"HTTP error occurred: {http_err}\nError: {error_message}")
29except requests.exceptions.RequestException as err:
30    # Handle other request exceptions
31    print(f"Other error occurred: {err}")

By utilizing streaming, even large files are downloaded efficiently. This technique is especially useful when file sizes increase.

Once you've downloaded a file, it's imperative to verify its contents to ensure a successful transfer. In our example, after downloading, you can open the file and print its content to confirm data integrity:

Python
Copy to clipboard
1# Open and read the downloaded file to verify its content
2try:
3    with open(f"downloaded_{note_name}", "r") as file:
4        content = file.read()
5    print(content)
6
7except IOError as io_err:
8    print(f"File error occurred: {io_err}")

If everything is functioning correctly, you should see an output similar to:

Plain text
Copy to clipboard
1Welcome to Your Notes! 📝
2
3This is a sample note that comes with the application.

This step is essential for data verification. The familiar error-handling techniques come into play once more, using try-except blocks to gracefully address any issues during the download and verification process.

In this lesson, you explored two methods for downloading files from an API: a straightforward approach for smaller files and a more efficient streaming method for larger files. You've practiced verifying file integrity by reading its contents post-download and reinforced your knowledge of error management. As you proceed to the practice exercises, you'll have the opportunity to apply these skills, reinforcing your ability to manage API interactions effectively. Keep experimenting with different files and settings, as this will further enhance your understanding and proficiency. Exciting topics await, such as file uploads and handling paginated responses. Your journey in mastering API interactions continues!