How deeply does Python Workout: 50 ten-minute exercises cover global statement?

Explains declaration behavior with runnable examples and cautions against global mutation, without developing implementation internals.

Global statement

As explained in Python Workout: 50 ten-minute exercises

The global statement declares that assignments and references to specified names in a function use the module-level global bindings.

A function normally creates a local variable when it assigns to a name. If the function must update the module-level binding instead, declare that name with global before retrieving or assigning it. section 6.5

Updating a module-level variable

x = 100 def foo(): global x x = 200 print(x) print(x) foo() print(x) The output is 100, 200, and 200: foo changes the existing global x rather than creating a separate local x. section 6.5

Without global, a function can use the same name locally without affecting the outer binding. Changing global state is usually discouraged, but can be necessary for an update such as a configuration parameter. section 6.5

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Python How-ToThe global keyword declares that assignments to a name in a function refer to the corresponding binding in the global scope.
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Python Workout, Second EditionThe global statement declares that assignments and name accesses in a function refer to a module-level global name.

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Related concepts

global variableconfigures · A global variable is a variable whose binding is accessible from broad program or module scope according to the language’s name-resolution rules.
nonlocal statementcontrasts with · A nonlocal statement makes a name assigned in a nested Python function refer to a binding in an enclosing function scope.
statementkind of · A statement is a syntactic program construct that performs an action, declaration, or control operation without necessarily producing an expression value.
bindingconfigures · Name binding is the association of an identifier with the program entity or value it denotes.
scopeuses · Scope is the region of a program in which names are visible and can be resolved according to the language’s lookup rules.

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