


Why NameResolutionError(self.host, self, e) from e and how to solve it
Mar 01, 2024 pm 01:20 PMThe reason for the error
NameResolutionError(self.host, self, e) from e is the exception type in the urllib3 library, The cause of this error is a DNS resolution failure, that is, the hostname or IP address that was attempted to be resolved could not be found. This may be caused by the entered URL address being incorrect, or the DNSserver being temporarily unavailable.
How to solve
There may be several ways to solve this error:
Check whether the entered URL address is correct and make sure it is accessible
Make sure the DNS server is available, you can try using the "ping" command on the command line to Test whether the DNS server is available
Try using the IP address instead of the hostname to access the website
If you are in a proxy environment, check whether the proxy configuration is correct.
Check the network connection to make sure the localhost can access the Internet.
Usage example
Yes, the following is a sample code that uses the urllib3 library to access the URL and handle the NameResolutionError exception:
import urllib3 Http = urllib3.PoolManager() try: response = http.request('GET', 'http://example.com') print(response.data) except urllib3.exceptions.NewConnectionError as e: print("Name resolution error: ", e)
In this example, we use the PoolManager() method of the urllib3 library to create an HTTP connection pool, and then use the request() method to issue a GET request. If a NameResolutionError exception occurs, it will be caught and error information printed.
Note: When using http.request(), if the entered url is incorrect or inaccessible, errors such as MaxRetryError and NewConnectionError will be thrown, and corresponding handling is required.
The above is the detailed content of Why NameResolutionError(self.host, self, e) from e and how to solve it. For more information, please follow other related articles on the PHP Chinese website!

Hot AI Tools

Undress AI Tool
Undress images for free

Undresser.AI Undress
AI-powered app for creating realistic nude photos

AI Clothes Remover
Online AI tool for removing clothes from photos.

Clothoff.io
AI clothes remover

Video Face Swap
Swap faces in any video effortlessly with our completely free AI face swap tool!

Hot Article

Hot Tools

Notepad++7.3.1
Easy-to-use and free code editor

SublimeText3 Chinese version
Chinese version, very easy to use

Zend Studio 13.0.1
Powerful PHP integrated development environment

Dreamweaver CS6
Visual web development tools

SublimeText3 Mac version
God-level code editing software (SublimeText3)

Hot Topics

The key to dealing with API authentication is to understand and use the authentication method correctly. 1. APIKey is the simplest authentication method, usually placed in the request header or URL parameters; 2. BasicAuth uses username and password for Base64 encoding transmission, which is suitable for internal systems; 3. OAuth2 needs to obtain the token first through client_id and client_secret, and then bring the BearerToken in the request header; 4. In order to deal with the token expiration, the token management class can be encapsulated and automatically refreshed the token; in short, selecting the appropriate method according to the document and safely storing the key information is the key.

To test the API, you need to use Python's Requests library. The steps are to install the library, send requests, verify responses, set timeouts and retry. First, install the library through pipinstallrequests; then use requests.get() or requests.post() and other methods to send GET or POST requests; then check response.status_code and response.json() to ensure that the return result is in compliance with expectations; finally, add timeout parameters to set the timeout time, and combine the retrying library to achieve automatic retry to enhance stability.

In Python, variables defined inside a function are local variables and are only valid within the function; externally defined are global variables that can be read anywhere. 1. Local variables are destroyed as the function is executed; 2. The function can access global variables but cannot be modified directly, so the global keyword is required; 3. If you want to modify outer function variables in nested functions, you need to use the nonlocal keyword; 4. Variables with the same name do not affect each other in different scopes; 5. Global must be declared when modifying global variables, otherwise UnboundLocalError error will be raised. Understanding these rules helps avoid bugs and write more reliable functions.

To create modern and efficient APIs using Python, FastAPI is recommended; it is based on standard Python type prompts and can automatically generate documents, with excellent performance. After installing FastAPI and ASGI server uvicorn, you can write interface code. By defining routes, writing processing functions, and returning data, APIs can be quickly built. FastAPI supports a variety of HTTP methods and provides automatically generated SwaggerUI and ReDoc documentation systems. URL parameters can be captured through path definition, while query parameters can be implemented by setting default values ??for function parameters. The rational use of Pydantic models can help improve development efficiency and accuracy.

Add timeout control to Python's for loop. 1. You can record the start time with the time module, and judge whether it is timed out in each iteration and use break to jump out of the loop; 2. For polling class tasks, you can use the while loop to match time judgment, and add sleep to avoid CPU fullness; 3. Advanced methods can consider threading or signal to achieve more precise control, but the complexity is high, and it is not recommended for beginners to choose; summary key points: manual time judgment is the basic solution, while is more suitable for time-limited waiting class tasks, sleep is indispensable, and advanced methods are suitable for specific scenarios.

How to efficiently handle large JSON files in Python? 1. Use the ijson library to stream and avoid memory overflow through item-by-item parsing; 2. If it is in JSONLines format, you can read it line by line and process it with json.loads(); 3. Or split the large file into small pieces and then process it separately. These methods effectively solve the memory limitation problem and are suitable for different scenarios.

In Python, the method of traversing tuples with for loops includes directly iterating over elements, getting indexes and elements at the same time, and processing nested tuples. 1. Use the for loop directly to access each element in sequence without managing the index; 2. Use enumerate() to get the index and value at the same time. The default index is 0, and the start parameter can also be specified; 3. Nested tuples can be unpacked in the loop, but it is necessary to ensure that the subtuple structure is consistent, otherwise an unpacking error will be raised; in addition, the tuple is immutable and the content cannot be modified in the loop. Unwanted values can be ignored by \_. It is recommended to check whether the tuple is empty before traversing to avoid errors.

Python default parameters are evaluated and fixed values ??when the function is defined, which can cause unexpected problems. Using variable objects such as lists as default parameters will retain modifications, and it is recommended to use None instead; the default parameter scope is the environment variable when defined, and subsequent variable changes will not affect their value; avoid relying on default parameters to save state, and class encapsulation state should be used to ensure function consistency.
