Backend Development
PHP Tutorial
How to match @usernames outside of the \[url\] tag without using assertions?
How to match @usernames outside of the \[url\] tag without using assertions?
Apr 01, 2025 am 09:39 AM
![How to match @usernames outside of the \[url\] tag without using assertions?](https://img.php.cn/upload/article/001/246/273/174294902013717.jpg)
Clever Match: Accurately extract @ usernames from non-[url] tags without assertions
In text processing, it is often necessary to extract strings of specific patterns. For example, from text containing username and URL tags, only extract not<url></url> @用戶名in the tag. This article provides a solution without using regular expression assertions.
Assume the text is as follows:
<code>[url=/space/4]@張三[/url] [url=/space/5]@李四[/url] @張三@張三[url=/space/6]@王五[/url] [url=/space/7]@趙六[/url] [url=/space/8]@wolegequ[/url]@sweet @haha</code>
The goal is to extract @張三, @sweet , @haha .
Traditional methods may use regular expressions and assertions, but this article takes a more clever approach to avoid assertions:
Step 1: Roughly match all @ usernames
First, use a simple regular expression to match all user names containing @ symbol:
import re text = '[url=/space/4]@Zhang San[/url] [url=/space/5]@Li Si[/url] @Zhang San@Zhang San[url=/space/6]@Wang Wu[/url] [url=/space/7]@Zhao Liu[/url] [url=/space/8]@wolegequ[/url]@sweet @haha' matches = re.findall(r'@([^@\[\]] )', text) # After matching the @ symbol, until @, [ or ] is encountered print(matches) # Output: ['Zhang San', 'Li Si', 'Zhang San', 'Zhang San', 'Wang Wu', 'Zhao Liu', 'wolegequ', 'sweet', 'haha']
Step 2: Accurate filtering and remove usernames from the tags
Next, the key is to filter out the<url></url> Username within the tag. We can do it through the following steps:
- Remove
<url></url>andTag: First, put all the text in<url></url>andTag removal. - Check whether the match exists: traverse all user names matched in the first step and determine whether they still exist in the processed text. Only user names that are not in the tag will be retained.
filtered_matches = []
temp_text = text.replace('[url]', '').replace('[/url]', '') #Remove tags for match in matches:
if f"@{match}" in temp_text: # Check whether the username is filtered_matches.append(match) in the processed text
print(filtered_matches) # Output: ['Zhang San', 'Zhang San', 'Zhang San', 'sweet', 'haha']
Final result:
Although @張三appeared three times in the final result, this fits the situation of the original text. If you need to deduplicate, you can add deduplication operation in the last step. This method effectively avoids the use of regular expression assertions, while achieving precise matching.
This revised answer provides a more detailed and clearer explanation of the process, improving readability and understanding. It also addresses the potential for duplicate matches in the final output, acknowledging this as a consequence of the original text's structure.
The above is the detailed content of How to match @usernames outside of the \[url\] tag without using assertions?. 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
What is Impossible Cloud Network (ICNT)? How? A comprehensive introduction to the ICN project that Binance will launch soon
Jul 07, 2025 pm 07:06 PM
Contents 1. What is ICN? 2. ICNT latest updates 3. Comparison and economic model between ICN and other DePIN projects and economic models 4. Conclusion of the next stage of the DePIN track At the end of May, ICN (ImpossibleCloudNetwork) @ICN_Protocol announced that it had received strategic investment in NGPCapital with a valuation of US$470 million. Many people's first reaction was: "Has Xiaomi invested in Web3?" Although this was not Lei Jun's direct move, the one who had bet on Xiaomi, Helium, and WorkFusion
2025 Stablecoin Investment Tutorial How to Choose a Safe Stablecoin Platform
Jul 07, 2025 pm 09:09 PM
How do novice users choose a safe and reliable stablecoin platform? This article recommends the Top 10 stablecoin platforms in 2025, including Binance, OKX, Bybit, Gate.io, HTX, KuCoin, MEXC, Bitget, CoinEx and ProBit, and compares and analyzes them from dimensions such as security, stablecoin types, liquidity, user experience, fee structure and additional functions. The data comes from CoinGecko, DefiLlama and community evaluation. It is recommended that novices choose platforms that are highly compliant, easy to operate and support Chinese, such as KuCoin and CoinEx, and gradually build confidence through a small number of tests.
How to avoid risks in the turmoil in the currency circle? The TOP3 stablecoin list is revealed
Jul 08, 2025 pm 07:27 PM
Against the backdrop of violent fluctuations in the cryptocurrency market, investors' demand for asset preservation is becoming increasingly prominent. This article aims to answer how to effectively hedge risks in the turbulent currency circle. It will introduce in detail the concept of stablecoin, a core hedge tool, and provide a list of TOP3 stablecoins by analyzing the current highly recognized options in the market. The article will explain how to select and use these stablecoins according to their own needs, so as to better manage risks in an uncertain market environment.
Global stablecoin market value PK! Who is the gold substitute in the bear market
Jul 08, 2025 pm 07:24 PM
This article will discuss the world's mainstream stablecoins and analyze which stablecoins have the risk aversion attribute of "gold substitute" in the market downward cycle (bear market). We will explain how to judge and choose a relatively stable value storage tool in a bear market by comparing the market value, endorsement mechanism, transparency, and comprehensively combining common views on the Internet, and explain this analysis process.
The popularity of the currency circle has returned, why do smart people have begun to quietly increase their positions? Look at the trend from the on-chain data and grasp the next round of wealth password!
Jul 09, 2025 pm 08:30 PM
As the market conditions pick up, more and more smart investors have begun to quietly increase their positions in the currency circle. Many people are wondering what makes them take decisively when most people wait and see? This article will analyze current trends through on-chain data to help readers understand the logic of smart funds, so as to better grasp the next round of potential wealth growth opportunities.
How to collect airdrops in the currency circle? Are free tokens risky? Airdrop participation strategy
Jul 07, 2025 pm 10:12 PM
Airdrops in the cryptocurrency field are a marketing promotion method for the project to distribute a certain number of tokens for free to community members or potential users. In this way, the project party hopes to increase the visibility of the tokens and attract more users to participate in the project, thereby expanding the size of the community and increasing the liquidity of the tokens. For users, airdrops provide opportunities to obtain project tokens without initial investment, and are one of the ways to get in touch with and understand new projects in the early stage.
Virtual Currency Stable Coins Ranking Which is the 'safe haven' in the currency circle
Jul 08, 2025 pm 07:30 PM
This article will introduce several mainstream stablecoins and explain in depth how to evaluate the security of a stablecoin from multiple dimensions such as transparency and compliance, so as to help you understand which stablecoins are generally considered relatively reliable choices in the market, and learn how to judge their "hazard-haven" attributes on your own.
Bitcoin breaks new highs, Dogecoin rebounds strongly, will Ethereum keep up with the pace
Jul 09, 2025 pm 08:24 PM
Recently, Bitcoin hit a new high, Dogecoin ushered in a strong rebound and the market was hot. Next, we will analyze the market drivers and technical aspects to determine whether Ethereum still has opportunities to follow the rise.
