Chunked transfer encoding is a data transfer mechanism in HTTP/1.1 that allows a server to send a response in pieces (chunks) rather than as a single block. This can be useful for streaming large or dynamic content without knowing the entire content size beforehand. Each chunk is preceded by its size in hexadecimal form and followed by \r\n. The end of the chunks is denoted by a zero-size chunk.
urllib3 is a powerful HTTP client for Python that supports many features of the HTTP protocol, including chunked transfer encoding. When you use urllib3, it abstracts away the handling of chunked transfer encoding, so you generally don't need to deal with it directly. The library will read the chunks and present you with the complete content once it has been fully retrieved.
Here's an example of how to handle responses with chunked transfer encoding using urllib3:
import urllib3
# Create a PoolManager instance for sending requests.
http = urllib3.PoolManager()
# Send a GET request to a URL that responds with chunked encoding.
response = http.request('GET', 'http://httpbin.org/stream/20', preload_content=False)
# The 'preload_content=False' parameter prevents urllib3 from downloading the
# entire response immediately. It allows you to stream the response content.
try:
# Read 1024 bytes at a time.
for chunk in response.stream(1024):
print(chunk)
finally:
# Always close the response once you're done with it.
response.release_conn()
In the above example, httpbin.org/stream/20 is a test endpoint that streams 20 chunks of data. The preload_content=False argument tells urllib3 not to download the whole response immediately, which allows us to stream the response content chunk by chunk.
The response.stream(1024) call is used to iterate over the response in chunks of 1024 bytes. You can adjust the chunk size to whatever is appropriate for your application. After processing the chunks, it's important to call response.release_conn() to release the connection back to the pool for reuse.
If the server sends a chunked response, urllib3 will handle the encoding transparently, and you will receive the unchunked data when you read from the response. There's no need to manually decode the chunked transfer encoding, as urllib3 takes care of that for you.
If you need to handle chunked transfer encoding manually for some reason (which is rare), you would need to parse the chunk sizes and data yourself. However, this is outside the typical use case for urllib3 since the library is designed to abstract away such low-level details.
