Professional IronPython

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CHAPTER 3
ImplementIng Structured language elementS
STRINgINg STATEmENTS TogETHER
A basic IronPython application begins as a series of statements, as a procedure. These statements 
perform some task at the command line or within a window, depending on which IronPython inter-
preter you use. This initial execution path is called the main function, even though there really isn’t 
a function — simply a set of statements.
A lot of people feel uncomfortable with the open feel of IronPython’s main function so they create 
something that looks a bit more like what they’re used to using, as shown in Listing 3-1.
LISTINg 3-1: 
 Creating an actual main() function
import sys
# Create a main() function that everyone can recognize.
def main(argv = None):
# Obtain the command line arguments.
if argv is None:
argv = sys.argv
# Display the command line arguments.
for ThisArg in argv:
print ThisArg
# Pause after the debug session.
raw_input(‘Press any key to continue...’)
# Call the main() function.
if __name__ == “__main__“:
main()
This code shows a few interesting structural features of IronPython, which is why it’s such a good 
example to start with. The code actually begins with a comparison of 
__name__
to 
“__main__“
. It 
turns out that 
__name__
always contains the name of the current function. Using 
__name__
makes
it possible for your application to detect its position in the execution loop.
Most programming languages provide an equivalent of the 
main()
 function 
described in Listing 3-1. Even C# and Visual Basic have a 
main()
-type function 
that creates the initial form. Whether you actually use a 
main()
 function in your 
applications depends upon how you expect other developers to interact with 
your code. The examples in this book don’t rely on a main function for the sake 
of clarity, but you might want to consider including one when developers are 
used to working with 
main()
 as part of their coding experience. Of course, you 
can call 
main()
 anything you like to match the programming language that your 
developers normally use.
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