Backend Development
Python Tutorial
Why does the `is` operator behave differently with non-cached integers inside and outside functions in Python?
The is operator behaves unexpectedly with non-cached integers
The is operator in Python is used to compare the identity of two objects, meaning it checks if they refer to the same object in memory. However, when dealing with non-cached integers, the is operator can behave in an unexpected way.
If you evaluate the is operator on two integers within a function, it will return True, indicating that they refer to the same object. However, if you evaluate the same is operator outside the function, it will return False, indicating that they refer to different objects.
This is because of the way Python handles integer caching. For integers within the range [-5, 256], Python caches the integer objects and reuses them for subsequent references. This means that when you assign an integer within this range to multiple variables within a function, they all refer to the same cached object, and hence the is operator returns True.
However, when you assign an integer outside a function, it creates a new integer object and does not use the cached object. Therefore, when you compare two integers outside a function, they refer to different objects, and the is operator returns False.
To avoid this unexpected behavior, it is recommended to use the equality operator (==) to compare the values of integers, rather than the is operator.
The above is the detailed content of Why does the `is` operator behave differently with non-cached integers inside and outside functions in Python?. For more information, please follow other related articles on the PHP Chinese website!
Building High-Performance Computing Solutions with PythonJul 21, 2025 am 03:17 AMPythoncanbeusedeffectivelyforhigh-performancecomputing(HPC)byleveragingspecifictoolsandtechniques.1)UsecompiledextensionslikeNumPy,SciPy,Cython,andNumbaforfasternumericalcomputations.2)TakeadvantageofparallelismwithmultiprocessingforCPU-boundtasksand
Factory Method Pattern in PythonJul 21, 2025 am 03:15 AMThe factory method pattern is a design pattern that instantiates specific classes through subclass decisions. It defines an interface to create objects, delaying the creation of objects to subclass processing, thereby achieving decoupling. This mode is suitable for scenarios such as hidden object creation details, uncertain future subclass types, and the need to call different objects in a unified interface. The implementation steps include: defining the base class or interface; creating multiple subclasses; writing factory functions or methods that return different instances according to parameters. Factory methods can be further encapsulated into classes to facilitate management of complex logic. When using it, you should pay attention to avoiding too many conditional judgments, preventing business logic from being mixed into the factory, avoiding over-design. It is also recommended to deal with abnormal inputs, keep the logic simple, and use it only when scalability is required.
Building a Chatbot with Python NLTKJul 21, 2025 am 03:12 AMIt is feasible to use Python and NLTK as chatbots, but the goals and methods need to be clarified. 1. Install Python and NLTK and download the necessary corpus such as punkt, stopwords and wordnet. 2. The implementation process includes text preprocessing (word segmentation, stop word deactivation, word shape restoration), intent recognition or keyword matching, and response generation. 3. Simple response can be achieved through keyword matching, or classification models can be trained to improve the effect. 4. Extension directions include introducing more powerful NLP tools such as spaCy or Transformers, maintaining Q&A databases, and avoiding too much hardcoded logic. In short, it is suitable for introductory and small projects, with low deployment costs but strong controllability.
Image Processing with Python PillowJul 21, 2025 am 03:11 AMPillow library image processing is very simple and suitable for daily operations. 1. Install pipinstallpillow and import the Image module to start; 2. You can open the picture and view width, height, format and other information; 3. Use crop to extract specific areas; 4. Use resize to zoom, pay attention to maintaining the proportion and avoiding deformation; 5. Use the draw.text method to add text watermarks, and specify the font path, position and color; 6. Use the paste method to overlay transparent layers in the image watermark; 7. Filter processing supports turning grayscale images, adjusting brightness contrast, etc.; 8. Although the Pillow function is basic, it is practical, and mastering common methods and document query can quickly complete the requirements.
Python for Distributed ComputingJul 21, 2025 am 03:03 AMPython is widely used in distributed computing because of its rich ecosystem and efficient development. 1. Distributed computing is to split tasks into multiple machines to perform to improve efficiency. Python is chosen because it has many libraries, easy to debug, and strong compatibility. 2. Common frameworks include Celery (asynchronous tasks), Dask (data science), PySpark (big data processing), and Ray (high-performance scheduling). 3. Celery can be used to build a simple system: install dependencies, write tasks, start worker, and trigger tasks. 4. Note points include task granularity, data lightweighting, failure retry, monitoring logs and task dependency management.
Python Regular Expressions TutorialJul 21, 2025 am 03:02 AMRegular expressions are used in Python to find, match, and replace text patterns. 1. Use re.search and re.match to determine whether the text contains a specific pattern. The former searches for the entire string, while the latter only starts from the beginning. 2. Extract content through brackets, such as using match.group(1) to obtain the required part when extracting the email address; 3. Use re.sub to replace sensitive words or format text, such as replacing the email with [EMAIL]; 4. Notes include escaping special characters, controlling greedy matching, ignoring uppercase and uppercase case and multi-line matching. Mastering these can quickly process text on mobile phones.
Building Cross-Platform Mobile Apps with Python BeeWareJul 21, 2025 am 03:01 AMBeeWare is a tool for developing cross-platform mobile applications using Python, which enables a truly native experience through native controls. 1. It is based on the TogaUI toolkit and Briefcase packaging tool, and supports macOS, Windows, Linux, iOS and Android platforms; 2. Unlike Kivy, Flutter or ReactNative, it directly calls the platform API without bridging; 3. It is suitable for developers familiar with Python to carry out rapid prototype development and data-driven gadget-based app development; 4. The current version is more suitable for small and medium-sized or experimental projects, and there are still restrictions on scenarios with high requirements for complex UI and performance; 5. The steps to get started include installing Be
Implementing Edge Computing Solutions with PythonJul 21, 2025 am 02:56 AMThe core of Python's implementation of edge computing is to bring data processing and decision-making close to data sources, and improve efficiency by deploying lightweight services, executing local inference and establishing a cache upload mechanism. 1. Use Flask or FastAPI to deploy local API services on edge nodes to achieve fast response; 2. Use Python to perform data preprocessing and lightweight AI inference to reduce the amount of uploaded data; 3. Use SQLite to implement local cache and combine asynchronous upload to cope with network instability. At the same time, you need to pay attention to details such as dependency control, model size, retry strategy and resource occupation.


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

Dreamweaver CS6
Visual web development tools

SecLists
SecLists is the ultimate security tester's companion. It is a collection of various types of lists that are frequently used during security assessments, all in one place. SecLists helps make security testing more efficient and productive by conveniently providing all the lists a security tester might need. List types include usernames, passwords, URLs, fuzzing payloads, sensitive data patterns, web shells, and more. The tester can simply pull this repository onto a new test machine and he will have access to every type of list he needs.

EditPlus Chinese cracked version
Small size, syntax highlighting, does not support code prompt function

MinGW - Minimalist GNU for Windows
This project is in the process of being migrated to osdn.net/projects/mingw, you can continue to follow us there. MinGW: A native Windows port of the GNU Compiler Collection (GCC), freely distributable import libraries and header files for building native Windows applications; includes extensions to the MSVC runtime to support C99 functionality. All MinGW software can run on 64-bit Windows platforms.

SublimeText3 Chinese version
Chinese version, very easy to use







