Chapter 5 · Responses in Depth

Chapter goals: master status-code checking, JSON parsing, binary handling, and streaming responses.

5.1 Checking Status Codes

HTTP status codes indicate the outcome of a request:

Range	Meaning	Examples
2xx	Success	200 OK, 201 Created
3xx	Redirection	301 Moved, 304 Not Modified
4xx	Client error	400 Bad Request, 404 Not Found
5xx	Server error	500 Internal Server Error

import requests

resp = requests.get('https://httpbin.org/status/404')

# Option 1: check manually
if resp.status_code == 200:
    print('Success')
elif resp.status_code == 404:
    print('Not found')
else:
    print(f'Other status: {resp.status_code}')

# Option 2: the is_success property (True for 2xx)
if resp.is_success:
    print('Success')
else:
    print(f'Failed: {resp.status_code}')

# Option 3: raise_for_status() (recommended; raises on failure)
resp.raise_for_status()  # raises HTTPError if status >= 400

5.2 Handling JSON Responses

import requests
import json

resp = requests.get('https://api.github.com/users/octocat')

# Parse JSON
data = resp.json()
print(data['name'])

# Check whether it's a JSON response
if resp.headers.get('Content-Type', '').startswith('application/json'):
    data = resp.json()
else:
    print('Non-JSON response:', resp.text[:100])

# Handling JSON parse errors
try:
    data = resp.json()
except requests.exceptions.JSONDecodeError as e:
    print(f'JSON parsing failed: {e}')
    print('Raw response:', resp.text[:200])

5.3 Binary Response Handling

For images, files, audio and similar payloads:

import requests

# Download an image
resp = requests.get('https://httpbin.org/image/png')

# Save it to disk
with open('download.png', 'wb') as f:
    f.write(resp.content)

# Work with binary data in memory
image_data = resp.content
# Can be handed to PIL, cv2, etc.

5.4 Streaming Responses

Use stream=True for large files so the whole body isn't loaded into memory:

import requests

# Streaming download of a large file
with requests.get('https://httpbin.org/stream/20', stream=True) as resp:
    resp.raise_for_status()

    # Read content incrementally
    for line in resp.iter_lines():
        if line:
            print(line.decode('utf-8'))

# Downloading a large file to disk
url = 'https://httpbin.org/drip?numbytes=500000&delay=1'
with requests.get(url, stream=True) as resp:
    resp.raise_for_status()
    total = int(resp.headers.get('content-length', 0))

    with open('large_file.bin', 'wb') as f:
        for chunk in resp.iter_content(chunk_size=8192):
            if chunk:
                f.write(chunk)
                # Optional: show progress
                # print(f'\rDownloaded: {f.tell()}/{total}', end='')

iter_content() and iter_lines() are the key methods for stream processing.

5.5 Response Timeouts

import requests

# Set a timeout (seconds)
try:
    resp = requests.get('https://httpbin.org/delay/5', timeout=3)
except requests.exceptions.Timeout:
    print('Request timed out')

# Separate connect and read timeouts
resp = requests.get(url, timeout=(5, 10))  # (connect_timeout, read_timeout)

# httpx equivalent
import httpx
client = httpx.Client(timeout=10.0)
resp = client.get(url)

5.6 Chapter Summary

• Check outcomes via resp.status_code or resp.is_success;
• resp.raise_for_status() raises an exception on failure (recommended);
• Use .content for binary data and .json() for JSON;
• Handle large files with stream=True plus iter_content();
• Always set sensible timeouts.

🧪 随堂测验

点击你认为正确的选项。答错时会展示正确答案与原因解析。

1. When does resp.raise_for_status() raise an exception?

2. What is the main advantage of stream=True?

3. What does timeout=(5, 10) mean?

4. Which property should you use to handle binary responses such as images?

🛠️ Hands-On Exercises

1. Request a 404 from httpbin and check the status code using all three approaches.
2. Stream-download a file larger than 1 MB, recording elapsed time and memory usage.
3. Set a 2-second timeout against a slow endpoint and catch the Timeout exception.