Ao trabalhar com APIs web em Python, você frequentemente se deparará com situações em que suas requisições são negadas devido a problemas de autorização. Este laboratório guia você através da compreensão e do tratamento eficaz de respostas não autorizadas (401) ao usar a biblioteca requests do Python. Ao aprender técnicas adequadas de tratamento de erros, você poderá construir aplicações mais resilientes que gerenciam com elegância as falhas de autenticação.
Antes de mergulharmos no tratamento de respostas não autorizadas, é importante entender o que elas são e por que ocorrem.
Os códigos de status HTTP são números de três dígitos que os servidores enviam em resposta às requisições do cliente. Esses códigos são agrupados em cinco categorias:
O código de status 401 Unauthorized pertence à categoria 4xx e indica que a requisição não possui credenciais de autenticação válidas para o recurso de destino. Isso é diferente de uma resposta 403 Forbidden, que significa que o servidor entende a requisição, mas se recusa a autorizá-la.
Vamos começar criando um diretório para nosso projeto e instalando os pacotes necessários.
mkdir -p ~/project/python-auth-handling
cd ~/project/python-auth-handlingrequests:python -m venv venv
source venv/bin/activate
pip install requestsA saída deve ser semelhante a:
Collecting requests
Downloading requests-2.28.2-py3-none-any.whl (62 kB)
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ 62.8/62.8 KB 1.8 MB/s eta 0:00:00
[...additional output...]
Successfully installed certifi-2023.5.7 charset-normalizer-3.1.0 idna-3.4 requests-2.28.2 urllib3-1.26.16Agora, vamos criar um script Python para fazer uma requisição a um serviço que requer autenticação. Usaremos o serviço HTTPBin, que fornece endpoints para testar requisições HTTP.
Crie um novo arquivo chamado basic_request.py no WebIDE:
import requests
def make_request():
url = "https://httpbin.org/basic-auth/user/pass"
response = requests.get(url)
print(f"Status Code: {response.status_code}")
if response.status_code == 200:
print("Request was successful.")
print(f"Response content: {response.text}")
elif response.status_code == 401:
print("Unauthorized: Authentication is required and has failed.")
else:
print(f"Received unexpected status code: {response.status_code}")
if __name__ == "__main__":
make_request()Salve o arquivo e execute-o no terminal:
python basic_request.pyVocê deve ver uma saída semelhante a:
Status Code: 401
Unauthorized: Authentication is required and has failed.Isso ocorre porque estamos tentando acessar um endpoint que requer autenticação básica, mas não fornecemos nenhuma credencial.
Vamos modificar nosso script para imprimir mais detalhes sobre a resposta. Crie um novo arquivo chamado examine_response.py:
import requests
def examine_response():
url = "https://httpbin.org/basic-auth/user/pass"
response = requests.get(url)
print(f"Status Code: {response.status_code}")
print(f"Headers: {response.headers}")
## The WWW-Authenticate header provides details about how to authenticate
if 'WWW-Authenticate' in response.headers:
print(f"WWW-Authenticate: {response.headers['WWW-Authenticate']}")
## Try to get JSON content, but it might not be JSON or might be empty
try:
print(f"Content: {response.json()}")
except requests.exceptions.JSONDecodeError:
print(f"Content (text): {response.text}")
if __name__ == "__main__":
examine_response()Execute este script:
python examine_response.pyA saída incluirá os cabeçalhos da resposta e o cabeçalho WWW-Authenticate, que informa ao cliente como autenticar:
Status Code: 401
Headers: {'date': '...', 'content-type': '...', 'content-length': '0', 'connection': 'close', 'server': 'gunicorn/19.9.0', 'www-authenticate': 'Basic realm="Fake Realm"', 'access-control-allow-origin': '*', 'access-control-allow-credentials': 'true'}
WWW-Authenticate: Basic realm="Fake Realm"
Content (text):O cabeçalho WWW-Authenticate com o valor Basic realm="Fake Realm" indica que o servidor espera autenticação básica.
Agora que entendemos o que causa uma resposta 401 Unauthorized, vamos aprender como preveni-la fornecendo as credenciais de autenticação corretas.
A biblioteca requests do Python facilita a adição de autenticação básica às suas requisições. Você pode:
auth com uma tupla de nome de usuário e senhaHTTPBasicAuth de requests.authVamos modificar nosso script para incluir autenticação básica. Crie um novo arquivo chamado basic_auth.py:
import requests
from requests.auth import HTTPBasicAuth
def make_authenticated_request():
url = "https://httpbin.org/basic-auth/user/pass"
## Method 1: Using the auth parameter with a tuple
response1 = requests.get(url, auth=("user", "pass"))
print("Method 1: Using auth tuple")
print(f"Status Code: {response1.status_code}")
if response1.status_code == 200:
print(f"Response content: {response1.json()}")
else:
print(f"Request failed with status code: {response1.status_code}")
print("\n" + "-"*50 + "\n")
## Method 2: Using the HTTPBasicAuth class
response2 = requests.get(url, auth=HTTPBasicAuth("user", "pass"))
print("Method 2: Using HTTPBasicAuth class")
print(f"Status Code: {response2.status_code}")
if response2.status_code == 200:
print(f"Response content: {response2.json()}")
else:
print(f"Request failed with status code: {response2.status_code}")
if __name__ == "__main__":
make_authenticated_request()Execute o script:
python basic_auth.pyVocê deve ver uma resposta bem-sucedida com o código de status 200:
Method 1: Using auth tuple
Status Code: 200
Response content: {'authenticated': True, 'user': 'user'}
--------------------------------------------------
Method 2: Using HTTPBasicAuth class
Status Code: 200
Response content: {'authenticated': True, 'user': 'user'}Ambos os métodos alcançam o mesmo resultado - eles adicionam um cabeçalho Authorization à requisição com o nome de usuário e senha codificados em base64.
Vamos ver o que acontece quando fornecemos credenciais incorretas. Crie um novo arquivo chamado failed_auth.py:
import requests
def test_failed_authentication():
url = "https://httpbin.org/basic-auth/user/pass"
## Correct credentials
response_correct = requests.get(url, auth=("user", "pass"))
## Incorrect password
response_wrong_pass = requests.get(url, auth=("user", "wrong_password"))
## Incorrect username
response_wrong_user = requests.get(url, auth=("wrong_user", "pass"))
print("Correct credentials:")
print(f"Status Code: {response_correct.status_code}")
if response_correct.status_code == 200:
print(f"Response content: {response_correct.json()}")
print("\nIncorrect password:")
print(f"Status Code: {response_wrong_pass.status_code}")
print("\nIncorrect username:")
print(f"Status Code: {response_wrong_user.status_code}")
if __name__ == "__main__":
test_failed_authentication()Execute o script:
python failed_auth.pyVocê deve ver uma saída semelhante a:
Correct credentials:
Status Code: 200
Response content: {'authenticated': True, 'user': 'user'}
Incorrect password:
Status Code: 401
Incorrect username:
Status Code: 401Tanto o nome de usuário incorreto quanto a senha incorreta resultam em uma resposta 401 Unauthorized.
Agora, vamos implementar o tratamento de erros para falhas de autenticação. Crie um novo arquivo chamado handle_auth_errors.py:
import requests
from requests.exceptions import HTTPError
def make_authenticated_request(username, password):
url = "https://httpbin.org/basic-auth/user/pass"
try:
response = requests.get(url, auth=(username, password))
response.raise_for_status() ## Raises an HTTPError for bad responses (4xx or 5xx)
print(f"Authentication successful!")
print(f"Response content: {response.json()}")
return response
except HTTPError as e:
if response.status_code == 401:
print(f"Authentication failed: Invalid credentials")
## You might want to retry with different credentials here
return handle_authentication_failure()
else:
print(f"HTTP Error occurred: {e}")
return None
except Exception as e:
print(f"An error occurred: {e}")
return None
def handle_authentication_failure():
## In a real application, you might prompt the user for new credentials
## or use a token refresh mechanism
print("Attempting to authenticate with default credentials...")
return make_authenticated_request("user", "pass")
if __name__ == "__main__":
## First, try with incorrect credentials
print("Trying with incorrect credentials:")
make_authenticated_request("wrong_user", "wrong_pass")
print("\n" + "-"*50 + "\n")
## Then, try with correct credentials
print("Trying with correct credentials:")
make_authenticated_request("user", "pass")Execute o script:
python handle_auth_errors.pyA saída deve mostrar como o erro é tratado:
Trying with incorrect credentials:
Authentication failed: Invalid credentials
Attempting to authenticate with default credentials...
Authentication successful!
Response content: {'authenticated': True, 'user': 'user'}
--------------------------------------------------
Trying with correct credentials:
Authentication successful!
Response content: {'authenticated': True, 'user': 'user'}Este script demonstra um padrão simples de tratamento de erros onde nós:
raise_for_status() para lançar uma exceção para respostas 4xx/5xxEm aplicações do mundo real, você frequentemente precisa de estratégias mais avançadas para lidar com a autenticação. Vamos explorar algumas técnicas comuns.
Muitas APIs modernas usam autenticação baseada em token em vez de autenticação básica. OAuth 2.0 é um protocolo comum que usa tokens para autenticação e autorização.
Vamos criar um script que simula a autenticação baseada em token. Crie um arquivo chamado token_auth.py:
import requests
import time
import json
## Simulated token storage - in a real app, this might be a database or secure storage
TOKEN_FILE = "token.json"
def get_stored_token():
"""Retrieve the stored token if it exists."""
try:
with open(TOKEN_FILE, "r") as f:
token_data = json.load(f)
## Check if token is expired
if token_data.get("expires_at", 0) > time.time():
return token_data["access_token"]
except (FileNotFoundError, json.JSONDecodeError):
pass
return None
def save_token(token, expires_in=3600):
"""Save the token with expiration time."""
token_data = {
"access_token": token,
"expires_at": time.time() + expires_in
}
with open(TOKEN_FILE, "w") as f:
json.dump(token_data, f)
def get_new_token():
"""Simulate obtaining a new token from an authentication service."""
## In a real application, this would make a request to the auth server
print("Obtaining new access token...")
## Simulating a token generation
new_token = f"simulated_token_{int(time.time())}"
save_token(new_token)
return new_token
def make_authenticated_request(url):
"""Make a request with token authentication, refreshing if needed."""
## Try to get the stored token
token = get_stored_token()
## If no valid token exists, get a new one
if not token:
token = get_new_token()
## Make the authenticated request
headers = {"Authorization": f"Bearer {token}"}
response = requests.get(url, headers=headers)
## If unauthorized, the token might be invalid - get a new one and retry
if response.status_code == 401:
print("Token rejected. Getting a new token and retrying...")
token = get_new_token()
headers = {"Authorization": f"Bearer {token}"}
response = requests.get(url, headers=headers)
return response
## For testing, we'll use httpbin's bearer auth endpoint
if __name__ == "__main__":
## Using httpbin.org/bearer which checks for the Authorization header
url = "https://httpbin.org/bearer"
## First, delete any existing token to simulate a fresh start
try:
import os
os.remove(TOKEN_FILE)
except FileNotFoundError:
pass
print("First request (should obtain a new token):")
response = make_authenticated_request(url)
print(f"Status code: {response.status_code}")
print(f"Response: {response.json()}")
print("\nSecond request (should use the stored token):")
response = make_authenticated_request(url)
print(f"Status code: {response.status_code}")
print(f"Response: {response.json()}")Execute o script:
python token_auth.pyA saída deve ser semelhante a:
First request (should obtain a new token):
Obtaining new access token...
Status code: 200
Response: {'authenticated': True, 'token': 'simulated_token_1623456789'}
Second request (should use the stored token):
Status code: 200
Response: {'authenticated': True, 'token': 'simulated_token_1623456789'}Este script demonstra a autenticação baseada em token com atualização automática do token quando um token é rejeitado.
Às vezes, falhas de autenticação podem ser temporárias. Vamos implementar um mecanismo de retentativa com backoff exponencial. Crie um arquivo chamado retry_auth.py:
import requests
import time
import random
def make_request_with_retry(url, auth, max_retries=3, backoff_factor=0.5):
"""
Makes a request with retry logic and exponential backoff
Args:
url: URL to request
auth: Authentication tuple (username, password)
max_retries: Maximum number of retry attempts
backoff_factor: Factor by which to increase the delay between retries
"""
retries = 0
while retries <= max_retries:
try:
response = requests.get(url, auth=auth, timeout=10)
## If successful, return the response
if response.status_code == 200:
return response
## If unauthorized, we might want to handle differently
if response.status_code == 401:
print(f"Attempt {retries+1}/{max_retries+1}: Authentication failed")
## In a real app, we might refresh tokens here or prompt for new credentials
else:
print(f"Attempt {retries+1}/{max_retries+1}: Failed with status code {response.status_code}")
## If we've reached max retries, give up
if retries == max_retries:
print("Maximum retry attempts reached.")
return response
## Calculate delay with exponential backoff and jitter
delay = backoff_factor * (2 ** retries) + random.uniform(0, 0.1)
print(f"Retrying in {delay:.2f} seconds...")
time.sleep(delay)
retries += 1
except requests.exceptions.RequestException as e:
print(f"Request exception: {e}")
## If we've reached max retries, give up
if retries == max_retries:
print("Maximum retry attempts reached.")
raise
## Calculate delay with exponential backoff and jitter
delay = backoff_factor * (2 ** retries) + random.uniform(0, 0.1)
print(f"Retrying in {delay:.2f} seconds...")
time.sleep(delay)
retries += 1
if __name__ == "__main__":
url = "https://httpbin.org/basic-auth/user/pass"
print("Testing with incorrect credentials:")
response = make_request_with_retry(url, auth=("wrong_user", "wrong_pass"))
print(f"Final status code: {response.status_code}")
print("\nTesting with correct credentials:")
response = make_request_with_retry(url, auth=("user", "pass"))
print(f"Final status code: {response.status_code}")
print(f"Response content: {response.json()}")Execute o script:
python retry_auth.pyA saída deve ser semelhante a:
Testing with incorrect credentials:
Attempt 1/4: Authentication failed
Retrying in 0.54 seconds...
Attempt 2/4: Authentication failed
Retrying in 1.05 seconds...
Attempt 3/4: Authentication failed
Retrying in 2.08 seconds...
Attempt 4/4: Authentication failed
Maximum retry attempts reached.
Final status code: 401
Testing with correct credentials:
Final status code: 200
Response content: {'authenticated': True, 'user': 'user'}Este script demonstra um mecanismo de retentativa com backoff exponencial, que é um padrão comum ao lidar com requisições de rede que podem falhar temporariamente.
Para múltiplas requisições ao mesmo serviço, é frequentemente mais eficiente criar uma sessão que manterá as informações de autenticação. Crie um arquivo chamado auth_session.py:
import requests
def create_authenticated_session(base_url, username, password):
"""
Creates and returns a requests session with basic authentication
Args:
base_url: Base URL for the API
username: Username for authentication
password: Password for authentication
Returns:
A configured requests.Session object
"""
session = requests.Session()
session.auth = (username, password)
session.headers.update({
'User-Agent': 'MyApp/1.0',
'Accept': 'application/json'
})
## Test the authentication
test_url = f"{base_url}/basic-auth/{username}/{password}"
try:
response = session.get(test_url)
response.raise_for_status()
print(f"Authentication successful for user: {username}")
except requests.exceptions.HTTPError as e:
print(f"Authentication failed: {e}")
## In a real app, you might raise an exception here or handle it differently
return session
def make_authenticated_requests(session, base_url):
"""
Makes multiple requests using the authenticated session
Args:
session: The authenticated requests.Session
base_url: Base URL for the API
"""
## Make a request to a different endpoint
response1 = session.get(f"{base_url}/get")
print(f"\nRequest 1 status code: {response1.status_code}")
print(f"Request 1 response: {response1.json()}")
## Make another request
response2 = session.get(f"{base_url}/headers")
print(f"\nRequest 2 status code: {response2.status_code}")
print(f"Request 2 response: {response2.json()}")
if __name__ == "__main__":
base_url = "https://httpbin.org"
## Create an authenticated session
session = create_authenticated_session(base_url, "user", "pass")
## Use the session for multiple requests
make_authenticated_requests(session, base_url)Execute o script:
python auth_session.pyA saída deve ser semelhante a:
Authentication successful for user: user
Request 1 status code: 200
Request 1 response: {'args': {}, 'headers': {...}, 'origin': '...', 'url': 'https://httpbin.org/get'}
Request 2 status code: 200
Request 2 response: {'headers': {...}}Usar uma sessão tem várias vantagens:
Em aplicações do mundo real, você frequentemente encontra cenários de autenticação mais complexos. Vamos explorar alguns exemplos práticos e as melhores práticas.
A biblioteca requests permite que você crie manipuladores de autenticação personalizados, subclassificando a classe requests.auth.AuthBase. Isso é útil ao trabalhar com APIs que possuem esquemas de autenticação personalizados.
Crie um arquivo chamado custom_auth.py:
import requests
from requests.auth import AuthBase
import time
import hashlib
class CustomAuth(AuthBase):
"""
Example of a custom authentication mechanism that adds a timestamp and HMAC signature
This is similar to how many APIs authenticate requests (like AWS, Stripe, etc.)
"""
def __init__(self, api_key, api_secret):
self.api_key = api_key
self.api_secret = api_secret
def __call__(self, request):
## Add timestamp to the request
timestamp = str(int(time.time()))
## Add the API key and timestamp as headers
request.headers['X-API-Key'] = self.api_key
request.headers['X-Timestamp'] = timestamp
## Create a signature based on the request
## In a real implementation, this would include more request elements
method = request.method
path = request.path_url
## Create a simple signature (in real apps, use proper HMAC)
signature_data = f"{method}{path}{timestamp}{self.api_secret}".encode('utf-8')
signature = hashlib.sha256(signature_data).hexdigest()
## Add the signature to the headers
request.headers['X-Signature'] = signature
return request
def test_custom_auth():
"""Test our custom authentication with httpbin.org"""
url = "https://httpbin.org/headers"
## Create our custom auth handler
auth = CustomAuth(api_key="test_key", api_secret="test_secret")
## Make the request with our custom auth
response = requests.get(url, auth=auth)
print(f"Status Code: {response.status_code}")
print(f"Response Headers: {response.json()}")
## Verify our custom headers were sent
headers = response.json()['headers']
for header in ['X-Api-Key', 'X-Timestamp', 'X-Signature']:
if header.upper() in headers:
print(f"{header} was sent: {headers[header.upper()]}")
else:
print(f"{header} was not found in the response")
if __name__ == "__main__":
test_custom_auth()Execute o script:
python custom_auth.pyA saída deve incluir os cabeçalhos personalizados na resposta:
Status Code: 200
Response Headers: {'headers': {'Accept': '*/*', 'Accept-Encoding': 'gzip, deflate', 'Host': 'httpbin.org', 'User-Agent': 'python-requests/2.28.2', 'X-Api-Key': 'test_key', 'X-Signature': '...', 'X-Timestamp': '1623456789'}}
X-Api-Key was sent: test_key
X-Timestamp was sent: 1623456789
X-Signature was sent: ...Este exemplo mostra como implementar um esquema de autenticação personalizado que inclui um timestamp e uma assinatura, semelhante ao que muitas APIs comerciais usam.
Muitas APIs implementam limites de taxa para evitar abusos. Quando você excede o limite de taxa, o servidor normalmente responde com um código de status 429 Too Many Requests. Vamos criar um script para lidar com esse cenário.
Crie um arquivo chamado rate_limit_handler.py:
import requests
import time
def make_request_with_rate_limit_handling(url, max_retries=5):
"""
Makes a request with handling for rate limits (429 responses)
Args:
url: URL to request
max_retries: Maximum number of retry attempts
"""
retries = 0
while retries <= max_retries:
response = requests.get(url)
## If not rate limited, return the response
if response.status_code != 429:
return response
## We got rate limited, check if we have retry information
retry_after = response.headers.get('Retry-After')
## If we have retry information, wait that long
if retry_after:
wait_time = int(retry_after)
print(f"Rate limited. Waiting for {wait_time} seconds as specified by Retry-After header.")
time.sleep(wait_time)
else:
## If no retry information, use exponential backoff
wait_time = 2 ** retries
print(f"Rate limited. No Retry-After header. Using exponential backoff: {wait_time} seconds.")
time.sleep(wait_time)
retries += 1
if retries > max_retries:
print(f"Maximum retries ({max_retries}) exceeded.")
return response
## For demonstration, we'll simulate rate limiting using httpbin's status endpoint
if __name__ == "__main__":
## First request should succeed
print("Making request to endpoint that returns 200:")
response = make_request_with_rate_limit_handling("https://httpbin.org/status/200")
print(f"Final status code: {response.status_code}")
## Simulate being rate limited initially, then succeeding
print("\nSimulating rate limiting scenario:")
## We'll make 3 requests in sequence to different status codes (429, 429, 200)
## to simulate being rate limited twice and then succeeding
urls = [
"https://httpbin.org/status/429", ## First will be rate limited
"https://httpbin.org/status/429", ## Second will also be rate limited
"https://httpbin.org/status/200" ## Third will succeed
]
for i, url in enumerate(urls):
print(f"\nRequest {i+1}:")
response = make_request_with_rate_limit_handling(url, max_retries=1)
print(f"Final status code: {response.status_code}")Execute o script:
python rate_limit_handler.pyA saída simulará o tratamento de limites de taxa:
Making request to endpoint that returns 200:
Final status code: 200
Simulating rate limiting scenario:
Request 1:
Rate limited. No Retry-After header. Using exponential backoff: 1 seconds.
Rate limited. No Retry-After header. Using exponential backoff: 2 seconds.
Maximum retries (1) exceeded.
Final status code: 429
Request 2:
Rate limited. No Retry-After header. Using exponential backoff: 1 seconds.
Rate limited. No Retry-After header. Using exponential backoff: 2 seconds.
Maximum retries (1) exceeded.
Final status code: 429
Request 3:
Final status code: 200Isso demonstra como lidar com limites de taxa, respeitando o cabeçalho Retry-After ou implementando backoff exponencial.
Finalmente, vamos juntar tudo em uma solução abrangente de tratamento de erros. Crie um arquivo chamado complete_auth_handler.py:
import requests
import time
import random
import json
from requests.exceptions import RequestException, HTTPError, ConnectionError, Timeout
class AuthenticationManager:
"""Manages authentication tokens and credentials"""
def __init__(self, token_file="auth_token.json"):
self.token_file = token_file
self.token = self.load_token()
def load_token(self):
"""Load token from file storage"""
try:
with open(self.token_file, "r") as f:
token_data = json.load(f)
## Check if token is expired
if token_data.get("expires_at", 0) > time.time():
return token_data.get("access_token")
except (FileNotFoundError, json.JSONDecodeError):
pass
return None
def save_token(self, token, expires_in=3600):
"""Save token to file storage"""
token_data = {
"access_token": token,
"expires_at": time.time() + expires_in
}
with open(self.token_file, "w") as f:
json.dump(token_data, f)
def get_token(self):
"""Get a valid token, refreshing if necessary"""
if not self.token:
self.token = self.refresh_token()
return self.token
def refresh_token(self):
"""Refresh the authentication token"""
## In a real app, this would make a call to the auth server
print("Getting a new authentication token...")
new_token = f"refreshed_token_{int(time.time())}"
self.save_token(new_token)
return new_token
def invalidate_token(self):
"""Invalidate the current token"""
self.token = None
try:
with open(self.token_file, "w") as f:
json.dump({}, f)
except Exception:
pass
class APIClient:
"""Client for making API requests with comprehensive error handling"""
def __init__(self, base_url, auth_manager=None):
self.base_url = base_url
self.auth_manager = auth_manager or AuthenticationManager()
self.session = requests.Session()
def make_request(self, method, endpoint, **kwargs):
"""
Make an API request with comprehensive error handling
Args:
method: HTTP method (get, post, etc.)
endpoint: API endpoint to call
**kwargs: Additional arguments to pass to requests
Returns:
Response object or None if all retries failed
"""
url = f"{self.base_url}{endpoint}"
max_retries = kwargs.pop("max_retries", 3)
retry_backoff_factor = kwargs.pop("retry_backoff_factor", 0.5)
## Add authentication if we have an auth manager
if self.auth_manager:
token = self.auth_manager.get_token()
headers = kwargs.get("headers", {})
headers["Authorization"] = f"Bearer {token}"
kwargs["headers"] = headers
## Make the request with retries
for retry in range(max_retries + 1):
try:
request_func = getattr(self.session, method.lower())
response = request_func(url, **kwargs)
## Handle different status codes
if response.status_code == 200:
return response
elif response.status_code == 401:
print("Unauthorized: Token may be invalid")
if self.auth_manager and retry < max_retries:
print("Refreshing authentication token...")
self.auth_manager.invalidate_token()
token = self.auth_manager.get_token()
kwargs.get("headers", {})["Authorization"] = f"Bearer {token}"
continue
elif response.status_code == 429:
if retry < max_retries:
retry_after = response.headers.get("Retry-After")
if retry_after:
wait_time = int(retry_after)
else:
wait_time = retry_backoff_factor * (2 ** retry) + random.uniform(0, 0.1)
print(f"Rate limited. Waiting {wait_time:.2f} seconds before retry {retry + 1}/{max_retries}")
time.sleep(wait_time)
continue
else:
print("Rate limit retries exhausted")
elif 500 <= response.status_code < 600:
if retry < max_retries:
wait_time = retry_backoff_factor * (2 ** retry) + random.uniform(0, 0.1)
print(f"Server error ({response.status_code}). Retrying in {wait_time:.2f} seconds...")
time.sleep(wait_time)
continue
else:
print(f"Server error retries exhausted")
## If we get here, we're returning the response as-is
return response
except ConnectionError:
if retry < max_retries:
wait_time = retry_backoff_factor * (2 ** retry) + random.uniform(0, 0.1)
print(f"Connection error. Retrying in {wait_time:.2f} seconds...")
time.sleep(wait_time)
else:
print("Connection error retries exhausted")
raise
except Timeout:
if retry < max_retries:
wait_time = retry_backoff_factor * (2 ** retry) + random.uniform(0, 0.1)
print(f"Request timed out. Retrying in {wait_time:.2f} seconds...")
time.sleep(wait_time)
else:
print("Timeout retries exhausted")
raise
except RequestException as e:
print(f"Request failed: {e}")
raise
return None
def get(self, endpoint, **kwargs):
"""Make a GET request"""
return self.make_request("get", endpoint, **kwargs)
def post(self, endpoint, **kwargs):
"""Make a POST request"""
return self.make_request("post", endpoint, **kwargs)
## Additional methods can be added for other HTTP verbs
## Test the client with httpbin
if __name__ == "__main__":
## Clean any existing token files
import os
try:
os.remove("auth_token.json")
except FileNotFoundError:
pass
client = APIClient("https://httpbin.org")
print("Making a GET request to /get:")
response = client.get("/get")
print(f"Status code: {response.status_code}")
print(f"Response content: {response.json()}")
print("\nSimulating an unauthorized response:")
## For demonstration purposes, we'll use httpbin's status endpoint to simulate a 401
response = client.get("/status/401")
print(f"Status code: {response.status_code}")
print("\nSimulating a rate-limited response:")
## Simulate a 429 response
response = client.get("/status/429")
print(f"Status code: {response.status_code}")Execute o script:
python complete_auth_handler.pyA saída deve demonstrar o tratamento de erros abrangente:
Getting a new authentication token...
Making a GET request to /get:
Status code: 200
Response content: {'args': {}, 'headers': {...}, 'origin': '...', 'url': 'https://httpbin.org/get'}
Simulating an unauthorized response:
Unauthorized: Token may be invalid
Refreshing authentication token...
Getting a new authentication token...
Unauthorized: Token may be invalid
Refreshing authentication token...
Getting a new authentication token...
Unauthorized: Token may be invalid
Refreshing authentication token...
Getting a new authentication token...
Unauthorized: Token may be invalid
Status code: 401
Simulating a rate-limited response:
Rate limited. Waiting 0.54 seconds before retry 1/3
Rate limited. Waiting 1.04 seconds before retry 2/3
Rate limited. Waiting 2.07 seconds before retry 3/3
Rate limit retries exhausted
Status code: 429Este exemplo abrangente demonstra muitas das melhores práticas para lidar com autenticação e outros erros relacionados à API em uma aplicação Python pronta para produção.
Neste laboratório, você aprendeu como lidar efetivamente com respostas não autorizadas em requisições Python. Cobrimos vários aspectos importantes:
Entendendo a Autenticação HTTP e Códigos de Status: Você aprendeu o que as respostas 401 Unauthorized significam e como identificá-las em suas aplicações Python.
Autenticação Básica: Você implementou a autenticação básica usando tanto o parâmetro auth quanto a classe HTTPBasicAuth, e aprendeu como lidar com falhas de autenticação.
Estratégias Avançadas de Autenticação: Você explorou a autenticação baseada em token, lógica de retentativa com backoff exponencial e a criação de sessões autenticadas reutilizáveis.
Desafios de Autenticação do Mundo Real: Você implementou uma classe de autenticação personalizada, lidou com limites de taxa e criou uma solução abrangente de tratamento de erros para aplicações prontas para produção.
Essas técnicas ajudarão você a construir aplicações Python mais robustas e resilientes que podem lidar graciosamente com falhas de autenticação e outros erros relacionados ao interagir com APIs web.
Para aprendizado adicional, considere explorar:
