LEGB
LEGB is Python’s name-resolution order of local, enclosing-function, global, and built-in scopes.
Python How-To
The LEGB rule is Python's name-resolution rule that searches local, enclosing-function, global, and built-in scopes in that order.
- How it is used
- Resolves which object a name refers to when Python code uses variables across scopes.
- How deep it goes
- Explains the four-scope lookup order and works through a global-assignment failure and fix; mentions nonlocal without a worked example.
- Examples
- Contrasts a task database filename that remains `"N/A"` after local assignment with one updated to `"tasks.sqlite"` using `global`.
- What you can do after
- Diagnose/debug name lookup and choose global for module-level updates or nonlocal for enclosing-function updates.
Python Workout, Second Edition
The LEGB rule is Python's variable-lookup order of local, enclosing, global, and built-in scopes.
- How it is used
- Explains how Python resolves names inside and outside functions.
- How deep it goes
- Defines four lookup levels and works through shadowing, global rebinding, closures, and nonlocal state.
- Examples
- Uses nested functions, password generators, inner and outer x values, sum shadowing, and a nonlocal call counter.
- What you can do after
- Diagnose name-resolution surprises and choose local, global, or nonlocal bindings deliberately.
Python Workout: 50 ten-minute exercises
LEGB is Python's name-resolution order of local, enclosing-function, global, and built-in scopes.
- How it is used
- Explains Python name visibility, shadowing, nested-function behavior, and closure state.
- How deep it goes
- Defines lookup order and demonstrates closures and shadowing, while stopping short of a broader namespace implementation treatment.
- Examples
- Uses shadowed sum, inner-versus-outer variables, password generators, and functions retaining enclosing values.
- What you can do after
- Diagnose name-resolution errors, predict variable visibility, and design functions that retain enclosing state.
Read how Python Workout: 50 ten-minute exercises explains LEGB →
Related concepts
- scopeconfigures · Scope is the region of a program in which names are visible and can be resolved according to the language’s lookup rules.
- ICPOcontrasts with · ICPO is a mnemonic for Python attribute lookup order across an instance, its class, parent classes, and the object hierarchy.
- bindinguses · Name binding is the association of an identifier with the program entity or value it denotes.
- classuses · A class is a programming-language construct that defines a type’s structure or behavior and provides a basis for creating or representing objects.
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