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<title>6.21.4.8 Callback example
5: fixed arguments
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6.21.4.8 Callback example
5: fixed arguments
Things get slightly more interesting when you define callback options
that take a fixed number of arguments. Specifying that a callback
option takes arguments is similar to defining a
<code>store
</code> or
<code>append
</code>option: if you define
<tt class=
"member">type
</tt>, then the option takes one argument that
must be convertible to that type; if you further define
<code>nargs
</code>, then
the option takes
<code>nargs
</code> arguments.
Here's an example that just emulates the standard
<code>store
</code> action:
<div class=
"verbatim"><pre>
def store_value(option, opt_str, value, parser):
setattr(parser.values, option.dest, value)
parser.add_option(
"--foo",
action=
"callback", callback=store_value,
type=
"int", nargs=
3,
dest=
"foo")
Note that
<tt class=
"module">optparse
</tt> takes care of consuming
3 arguments and converting them
to integers for you; all you have to do is store them. (Or whatever;
obviously you don't need a callback for this example.)
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<span class=
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