


What is the LEGB (Local, Enclosing, Global, Built-in) rule for scope resolution in Python?
Jun 19, 2025 am 12:41 AMPython uses the LEGB rule to resolve variable names in different scopes. 1. Local (L): Variables defined inside the current function. 2. Enclosing (E): Variables in enclosing functions, searched from the inside out. 3. Global (G): Variables defined at the top level of a module or declared global. 4. Built-in (B): Predefined names like built-in functions and exceptions. Understanding and following this lookup order helps avoid scope-related bugs and ensures proper variable access.
Python uses the LEGB rule to determine which variable you're referring to when there are multiple variables with the same name in different scopes. This rule defines the order in which Python looks up variable names.
Here’s how it works:
Local (L)
This refers to variables defined inside the current function. When you assign a variable inside a function, it's considered local to that function by default.
For example:
def my_func(): x = 10 # x is local to my_func print(x) my_func()
Trying to access x
outside of my_func()
will result in an error because it only exists in the local scope.
Enclosing (E)
This applies to nested functions. If a variable isn't found in the local scope, Python checks any enclosing functions from the inside out.
Example:
def outer(): y = 20 def inner(): print(y) # y is in the enclosing scope inner() outer()
In this case, inner()
can access y
because it was defined in the outer function.
Global (G)
Variables defined at the top level of a module or declared as global
inside a function fall into this category.
Example:
z = 30 # global variable def show_z(): print(z) # can access global variable show_z()
If you want to modify a global variable inside a function, you must use the global
keyword:
global z
- Then you can assign a new value like
z = 50
Built-in (B)
These are special names that Python provides, like built-in functions and exceptions (print
, len
, TypeError
, etc.).
You can accidentally override these if you're not careful:
def len(): # Not a good idea! return "I overrode len!" print(len()) # Now this breaks normal behavior
To avoid issues:
- Don’t name your variables after built-in functions.
- Use tools like linters or IDEs to warn about such conflicts.
So, the LEGB rule helps Python decide where to look for a variable:
- First check Local,
- Then Enclosing,
- Then Global,
- And finally Built-in scopes.
It’s not magic, just a clear lookup order. Keep your naming clean and understand where each variable lives, and you’ll avoid most scope-related bugs.
The above is the detailed content of What is the LEGB (Local, Enclosing, Global, Built-in) rule for scope resolution in Python?. 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)

User voice input is captured and sent to the PHP backend through the MediaRecorder API of the front-end JavaScript; 2. PHP saves the audio as a temporary file and calls STTAPI (such as Google or Baidu voice recognition) to convert it into text; 3. PHP sends the text to an AI service (such as OpenAIGPT) to obtain intelligent reply; 4. PHP then calls TTSAPI (such as Baidu or Google voice synthesis) to convert the reply to a voice file; 5. PHP streams the voice file back to the front-end to play, completing interaction. The entire process is dominated by PHP to ensure seamless connection between all links.

To realize text error correction and syntax optimization with AI, you need to follow the following steps: 1. Select a suitable AI model or API, such as Baidu, Tencent API or open source NLP library; 2. Call the API through PHP's curl or Guzzle and process the return results; 3. Display error correction information in the application and allow users to choose whether to adopt it; 4. Use php-l and PHP_CodeSniffer for syntax detection and code optimization; 5. Continuously collect feedback and update the model or rules to improve the effect. When choosing AIAPI, focus on evaluating accuracy, response speed, price and support for PHP. Code optimization should follow PSR specifications, use cache reasonably, avoid circular queries, review code regularly, and use X

Use Seaborn's jointplot to quickly visualize the relationship and distribution between two variables; 2. The basic scatter plot is implemented by sns.jointplot(data=tips,x="total_bill",y="tip",kind="scatter"), the center is a scatter plot, and the histogram is displayed on the upper and lower and right sides; 3. Add regression lines and density information to a kind="reg", and combine marginal_kws to set the edge plot style; 4. When the data volume is large, it is recommended to use "hex"

The core idea of PHP combining AI for video content analysis is to let PHP serve as the backend "glue", first upload video to cloud storage, and then call AI services (such as Google CloudVideoAI, etc.) for asynchronous analysis; 2. PHP parses the JSON results, extract people, objects, scenes, voice and other information to generate intelligent tags and store them in the database; 3. The advantage is to use PHP's mature web ecosystem to quickly integrate AI capabilities, which is suitable for projects with existing PHP systems to efficiently implement; 4. Common challenges include large file processing (directly transmitted to cloud storage with pre-signed URLs), asynchronous tasks (introducing message queues), cost control (on-demand analysis, budget monitoring) and result optimization (label standardization); 5. Smart tags significantly improve visual

To integrate AI sentiment computing technology into PHP applications, the core is to use cloud services AIAPI (such as Google, AWS, and Azure) for sentiment analysis, send text through HTTP requests and parse returned JSON results, and store emotional data into the database, thereby realizing automated processing and data insights of user feedback. The specific steps include: 1. Select a suitable AI sentiment analysis API, considering accuracy, cost, language support and integration complexity; 2. Use Guzzle or curl to send requests, store sentiment scores, labels, and intensity information; 3. Build a visual dashboard to support priority sorting, trend analysis, product iteration direction and user segmentation; 4. Respond to technical challenges, such as API call restrictions and numbers

The core of PHP's development of AI text summary is to call external AI service APIs (such as OpenAI, HuggingFace) as a coordinator to realize text preprocessing, API requests, response analysis and result display; 2. The limitation is that the computing performance is weak and the AI ecosystem is weak. The response strategy is to leverage APIs, service decoupling and asynchronous processing; 3. Model selection needs to weigh summary quality, cost, delay, concurrency, data privacy, and abstract models such as GPT or BART/T5 are recommended; 4. Performance optimization includes cache, asynchronous queues, batch processing and nearby area selection. Error processing needs to cover current limit retry, network timeout, key security, input verification and logging to ensure the stable and efficient operation of the system.

String lists can be merged with join() method, such as ''.join(words) to get "HelloworldfromPython"; 2. Number lists must be converted to strings with map(str, numbers) or [str(x)forxinnumbers] before joining; 3. Any type list can be directly converted to strings with brackets and quotes, suitable for debugging; 4. Custom formats can be implemented by generator expressions combined with join(), such as '|'.join(f"[{item}]"foriteminitems) output"[a]|[

Pythoncanbeoptimizedformemory-boundoperationsbyreducingoverheadthroughgenerators,efficientdatastructures,andmanagingobjectlifetimes.First,usegeneratorsinsteadofliststoprocesslargedatasetsoneitematatime,avoidingloadingeverythingintomemory.Second,choos
