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<title>8.1 Complete Python programs
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8.1 Complete Python programs
While a language specification need not prescribe how the language
interpreter is invoked, it is useful to have a notion of a complete
Python program. A complete Python program is executed in a minimally
initialized environment: all built-in and standard modules are
available, but none have been initialized, except for
<tt class=
"module">sys
</tt>
(various system services),
<tt class=
"module">__builtin__
</tt> (built-in functions,
exceptions and
<code>None
</code>) and
<tt class=
"module">__main__
</tt>. The latter is used
to provide the local and global namespace for execution of the
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The syntax for a complete Python program is that for file input,
described in the next section.
The interpreter may also be invoked in interactive mode; in this case,
it does not read and execute a complete program but reads and executes
one statement (possibly compound) at a time. The initial environment
is identical to that of a complete program; each statement is executed
in the namespace of
<tt class=
"module">__main__
</tt>.
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Under
<span class=
"Unix">Unix
</span>, a complete program can be passed to the interpreter in
three forms: with the
<b class=
"programopt">-c
</b> <var>string
</var> command line option, as a
file passed as the first command line argument, or as standard input.
If the file or standard input is a tty device, the interpreter enters
interactive mode; otherwise, it executes the file as a complete
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<span class=
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2005.
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