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36 lines
1.3 KiB
XML
36 lines
1.3 KiB
XML
<!DOCTYPE qhelp PUBLIC
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"-//Semmle//qhelp//EN"
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"qhelp.dtd">
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<qhelp>
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<overview>
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<p>Python statements can access variables in both the local namespace and in the global namespace.
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When a local and a global variable have the same name, the local variable "shadows" or "hides" the
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global variable. When the variable is referenced, the variable with local scope is used unless you
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explicitly use the <code>global</code> statement to reference the global variable. This can lead to
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confusion as a reader of the code may expect the variable to refer to a global.
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</p>
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</overview>
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<recommendation>
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<p>Avoid using the same name for variables in local and global namespaces.</p>
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</recommendation>
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<example>
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<p>The following simple example shows how a local variable can "shadow" a global variable. The local
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variable should be renamed to make the code easier to interpret.</p>
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<sample src="ShadowGlobal.py" />
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</example>
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<references>
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<li>J. Lusth, <i>The Art and Craft of Programming - Python Edition</i>, Section: Scope. University of Alabama, 2012. (<a href="https://web.archive.org/web/20190919091129/http://troll.cs.ua.edu/ACP-PY/index_13.html">Published online</a>).</li>
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<li>Python Language Reference: <a href="http://docs.python.org/reference/simple_stmts.html#the-global-statement">The global statement</a>.</li>
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</references>
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</qhelp>
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