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<H3><A NAME="SECTION004171000000000000000"></A>
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2.1.7.1 Modules 
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<P>
The only special operation on a module is attribute access:
<tt><var>m</var>.<var>name</var></tt>, where <var>m</var> is a module and <var>name</var>
accesses a name defined in <var>m</var>'s symbol table.  Module attributes
can be assigned to.  (Note that the <tt class=keyword>import</tt> statement is not,
strictly speaking, an operation on a module object; <tt>import
<var>foo</var></tt> does not require a module object named <var>foo</var> to exist,
rather it requires an (external) <i>definition</i> for a module named
<var>foo</var> somewhere.)

<P>
A special member of every module is <tt class=member>__dict__</tt>.
This is the dictionary containing the module's symbol table.
Modifying this dictionary will actually change the module's symbol
table, but direct assignment to the <tt class=member>__dict__</tt> attribute is not
possible (i.e., you can write <tt><var>m</var>.__dict__['a'] = 1</tt>, which
defines <tt><var>m</var>.a</tt> to be <tt>1</tt>, but you can't write
<tt><var>m</var>.__dict__ = {}</tt>.

<P>
Modules built into the interpreter are written like this:
<tt>&lt;module 'sys' (built-in)&gt;</tt>.  If loaded from a file, they are
written as <tt>&lt;module 'os' from '/usr/local/lib/python1.5/os.pyc'&gt;</tt>.

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