python中Genarator函数用法分析
本文实例讲述了python中Genarator函数用法。分享给大家供大家参考。具体如下：
Generator函数的定义与普通函数的定义没有什么区别，只是在函数体内使用yield生成数据项即可。Generator函数可以被for循环遍历，而且可以通过next()方法获得yield生成的数据项。
def func(n):
for i in range(n):
yield i
for i in func(3):
print i
r=func(3)
print r.next()
print r.next()
print r.next()
print r.next()运行结果如下：
0 1 2 0 1 2 Traceback (most recent call last): File "generator.py", line 10, in <module> print r.next() StopIteration
yield保留字与return 语句的返回值和执行原理都不相同。yield生成值并不会中止程序的执行，返回值后程序继续往后执行。return 返回值后，程序将中止执行。
Generator函数一次只返回一个数据项，占用更少的内存。每次生成数据都要记录当前的状态，便于下一次生成数据。
当程序需要较高的性能或一次只需要一个值进行处理时，使用generator函数。当需要获取一次性一组元素的值时，使用序列。
函数里只要有了yield，这个函数就会被编译成一个generator 函数。generator函数object支持python iterator protocol。 每次调用这个对象的next，generator函数就执行到yield，获取到yield生成的值。如果函数返回，就抛出一个异常。这里有个概念就是generator 函数使用yield生成一个值，而不是返回一个值。生成之后函数还没结束，返回了函数就结束了。
>>> x = gensquares(5) >>> print x <generator object at 0x00B72D78> >>> print x.next() 0 >>> print x.next() 1 >>> print x.next() 4 >>> print x.next() 9 >>> print x.next() 16 >>> print x.next() Traceback (most recent call last): File "<stdin>", line 1, in ? StopIteration >>>
希望本文所述对大家的Python程序设计有所帮助。
Hot AI Tools
Undresser.AI Undress
AI-powered app for creating realistic nude photos
AI Clothes Remover
Online AI tool for removing clothes from photos.
Undress AI Tool
Undress images for free
Clothoff.io
AI clothes remover
AI Hentai Generator
Generate AI Hentai for free.
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
1377
52
Do mysql need to pay
Apr 08, 2025 pm 05:36 PM
MySQL has a free community version and a paid enterprise version. The community version can be used and modified for free, but the support is limited and is suitable for applications with low stability requirements and strong technical capabilities. The Enterprise Edition provides comprehensive commercial support for applications that require a stable, reliable, high-performance database and willing to pay for support. Factors considered when choosing a version include application criticality, budgeting, and technical skills. There is no perfect option, only the most suitable option, and you need to choose carefully according to the specific situation.
How to use mysql after installation
Apr 08, 2025 am 11:48 AM
The article introduces the operation of MySQL database. First, you need to install a MySQL client, such as MySQLWorkbench or command line client. 1. Use the mysql-uroot-p command to connect to the server and log in with the root account password; 2. Use CREATEDATABASE to create a database, and USE select a database; 3. Use CREATETABLE to create a table, define fields and data types; 4. Use INSERTINTO to insert data, query data, update data by UPDATE, and delete data by DELETE. Only by mastering these steps, learning to deal with common problems and optimizing database performance can you use MySQL efficiently.
MySQL can't be installed after downloading
Apr 08, 2025 am 11:24 AM
The main reasons for MySQL installation failure are: 1. Permission issues, you need to run as an administrator or use the sudo command; 2. Dependencies are missing, and you need to install relevant development packages; 3. Port conflicts, you need to close the program that occupies port 3306 or modify the configuration file; 4. The installation package is corrupt, you need to download and verify the integrity; 5. The environment variable is incorrectly configured, and the environment variables must be correctly configured according to the operating system. Solve these problems and carefully check each step to successfully install MySQL.
MySQL download file is damaged and cannot be installed. Repair solution
Apr 08, 2025 am 11:21 AM
MySQL download file is corrupt, what should I do? Alas, if you download MySQL, you can encounter file corruption. It’s really not easy these days! This article will talk about how to solve this problem so that everyone can avoid detours. After reading it, you can not only repair the damaged MySQL installation package, but also have a deeper understanding of the download and installation process to avoid getting stuck in the future. Let’s first talk about why downloading files is damaged. There are many reasons for this. Network problems are the culprit. Interruption in the download process and instability in the network may lead to file corruption. There is also the problem with the download source itself. The server file itself is broken, and of course it is also broken when you download it. In addition, excessive "passionate" scanning of some antivirus software may also cause file corruption. Diagnostic problem: Determine if the file is really corrupt
How to optimize MySQL performance for high-load applications?
Apr 08, 2025 pm 06:03 PM
MySQL database performance optimization guide In resource-intensive applications, MySQL database plays a crucial role and is responsible for managing massive transactions. However, as the scale of application expands, database performance bottlenecks often become a constraint. This article will explore a series of effective MySQL performance optimization strategies to ensure that your application remains efficient and responsive under high loads. We will combine actual cases to explain in-depth key technologies such as indexing, query optimization, database design and caching. 1. Database architecture design and optimized database architecture is the cornerstone of MySQL performance optimization. Here are some core principles: Selecting the right data type and selecting the smallest data type that meets the needs can not only save storage space, but also improve data processing speed.
Does mysql need the internet
Apr 08, 2025 pm 02:18 PM
MySQL can run without network connections for basic data storage and management. However, network connection is required for interaction with other systems, remote access, or using advanced features such as replication and clustering. Additionally, security measures (such as firewalls), performance optimization (choose the right network connection), and data backup are critical to connecting to the Internet.
Solutions to the service that cannot be started after MySQL installation
Apr 08, 2025 am 11:18 AM
MySQL refused to start? Don’t panic, let’s check it out! Many friends found that the service could not be started after installing MySQL, and they were so anxious! Don’t worry, this article will take you to deal with it calmly and find out the mastermind behind it! After reading it, you can not only solve this problem, but also improve your understanding of MySQL services and your ideas for troubleshooting problems, and become a more powerful database administrator! The MySQL service failed to start, and there are many reasons, ranging from simple configuration errors to complex system problems. Let’s start with the most common aspects. Basic knowledge: A brief description of the service startup process MySQL service startup. Simply put, the operating system loads MySQL-related files and then starts the MySQL daemon. This involves configuration
How to optimize database performance after mysql installation
Apr 08, 2025 am 11:36 AM
MySQL performance optimization needs to start from three aspects: installation configuration, indexing and query optimization, monitoring and tuning. 1. After installation, you need to adjust the my.cnf file according to the server configuration, such as the innodb_buffer_pool_size parameter, and close query_cache_size; 2. Create a suitable index to avoid excessive indexes, and optimize query statements, such as using the EXPLAIN command to analyze the execution plan; 3. Use MySQL's own monitoring tool (SHOWPROCESSLIST, SHOWSTATUS) to monitor the database health, and regularly back up and organize the database. Only by continuously optimizing these steps can the performance of MySQL database be improved.
