The stablecoin trading process includes the steps of registering an exchange, completing certification, buying or selling. First, choose a trusted exchange such as Binance, OKX, etc., and then complete KYC identity authentication, and then buy stablecoins through fiat currency recharge or OTC transactions. You can also transfer the stablecoins to the fund account and sell them through P2P transactions and withdraw them to the bank card or Alipay. When operating, you need to pay attention to choosing a regulated platform, confirm transaction security and handling fees.

To master Python web crawlers, you need to grasp three core steps: 1. Use requests to initiate a request, obtain web page content through get method, pay attention to setting headers, handling exceptions, and complying with robots.txt; 2. Use BeautifulSoup or XPath to extract data. The former is suitable for simple parsing, while the latter is more flexible and suitable for complex structures; 3. Use Selenium to simulate browser operations for dynamic loading content. Although the speed is slow, it can cope with complex pages. You can also try to find a website API interface to improve efficiency.

There are three common methods for deduplication in Python. 1. Use set deduplication: It is suitable for situations where you don’t care about the order, and is implemented through list(set(my_list)). The advantage is that it is simple and fast, and the disadvantage is to disrupt the order; 2. Manually judge the deduplication: By traversing the original list and determining whether the elements already exist in the new list, the elements that appear for the first time are retained, which is suitable for scenarios where order needs to be maintained; 3. dict.fromkeys() deduplication: supported by Python 3.7, implemented through list(dict.fromkeys(my_list)), which maintains both the order and the writing method is concise. It is recommended to use modern Python. Notes include first converting the structure when dealing with non-hashable elements. It is recommended to use large data sets.

To get started with quantum machine learning (QML), the preferred tool is Python, and libraries such as PennyLane, Qiskit, TensorFlowQuantum or PyTorchQuantum need to be installed; then familiarize yourself with the process by running examples, such as using PennyLane to build a quantum neural network; then implement the model according to the steps of data set preparation, data encoding, building parametric quantum circuits, classic optimizer training, etc.; in actual combat, you should avoid pursuing complex models from the beginning, paying attention to hardware limitations, adopting hybrid model structures, and continuously referring to the latest documents and official documents to follow up on development.

Blockchain browser is a must-have on-chain query tool for Web3 users. 1. It serves as a "search engine" in the decentralized world, allowing users to openly and transparently verify all records on the blockchain; 2. The core functions include querying transaction details, viewing account information, exploring block data and tracking smart contracts; 3. When tracking transactions, you need to obtain the transaction hash, select the browser corresponding to the public chain, and enter the hash to view the status, address, amount and fee details; 4. Confirm whether the transaction is successful through the browser is a key step to ensure the security of digital assets. Proficient use can help users better understand and participate in the blockchain ecosystem, thereby operating more safely and stably in the decentralized world.

Cross-chain transactions face technical difficulties such as differences in consensus mechanisms, unshared data, complex atomic guarantees, security issues and high latency costs. 1. Use relay network to achieve interchain data synchronization; 2. Use atomic exchange to achieve intermediary asset swaps; 3. Lock assets through cross-chain bridges and generate mapping tokens; 4. Use multi-chain aggregation protocol to integrate liquidity; in the future, it will optimize the cross-chain ecosystem by enhancing security, promoting standardized interfaces, improving user experience and strengthening decentralization, and provide safe and convenient support for the multi-chain circulation of altcoins.

To collect user behavior data, you need to record browsing, search, purchase and other information into the database through PHP, and clean and analyze it to explore interest preferences; 2. The selection of recommendation algorithms should be determined based on data characteristics: based on content, collaborative filtering, rules or mixed recommendations; 3. Collaborative filtering can be implemented in PHP to calculate user cosine similarity, select K nearest neighbors, weighted prediction scores and recommend high-scoring products; 4. Performance evaluation uses accuracy, recall, F1 value and CTR, conversion rate and verify the effect through A/B tests; 5. Cold start problems can be alleviated through product attributes, user registration information, popular recommendations and expert evaluations; 6. Performance optimization methods include cached recommendation results, asynchronous processing, distributed computing and SQL query optimization, thereby improving recommendation efficiency and user experience.

Blockchain confirmation time refers to the time it takes for a transaction to be broadcasted to be packaged by a block and written to the chain. The confirmation speeds of different chains vary. 1. Bitcoin produces blocks on average in 10 minutes, and it is recommended to confirm 6 times to ensure security; 2. Ethereum produces blocks in about 12 seconds, and 1-3 times can be confirmed, and most transactions are completed within 1 minute; 3. The BSC chain block time is about 3 seconds, suitable for high-frequency trading; 4. The TRON tide block time is 1-3 seconds, suitable for real-time transfer; 5. The Polygon block time is about 2 seconds, with low fees, and is widely used in DeFi and NFT. Trading hash (TxID) is required for query and confirmation status. Recommended platforms include: 1. Ouyi OKX, which supports multi-chain transaction query; 2. Binance, suitable for BSC chain; 3. Huobi HT