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The global Statement

The suite of statements in a function definition executes with a local namespace that is different from the global namespace. This means that all variables created within a function are local to that function. When the suite finishes, these working variables are discarded.

The overall Python session works in the global namespace. Every other context (e.g. within a function's suite), there is a distinct local namespace. Python offers us the global statement to change the namespace search rule.

global name ...

The global statement tells Python that the following names are part of the global namespace. The following example shows two functions that share a global variable.

ratePerHour= 45.50
def cost( hours ):
    global ratePerHour
    return hours * ratePerHour
def laborMaterials( hours, materials ):
    return cost(hours) + materials


The global statement has a consequence of tightly coupling pieces of software. This can lead to difficulty in maintenance and enhancement of the program. Classes and modules provide better ways to assemble complex programs.

As a general policy, we discourage use of the global statement.

  Published under the terms of the Open Publication License Design by Interspire