On Fri, Jul 10, 2009 at 5:52 PM, Tim<timlee...@yahoo.com> wrote: > > Hi, > I learned that a Python script is written in this way: > def main(): > ... > if __name__ == "__main__": > main() > > Today, when I read a script, I found it has a different way: > > def main(): > ... > > main() > > It can run as well. Can someone explain why and the rules that Python scripts > get run? >
You're thinking like a C or Java programmer. Python scripts are just that - scripts. They aren't compiled with a main() method for an entry point- it's interpreted. When you run a python script, everything that isn't indented is run, from top to bottom, in order. So for instance, when the interpreter sees the line def main() : pass it creates a function called main. If you were to have the statement x= 5 the value 5 would be assigned to x at that time. There are two ways to execute these scripts- by running them directly and by importing them into another module. The second way, with the main method, the script will be run any time it is imported. The first relies on the fact that any module run as a script has a __name__ attribute of "__main__" (usually it's the name of the module). The first program acts more like the C code would- the "main" part of it will only be run if that script is executed. > Thanks and regards, > Tim > > > > -- > http://mail.python.org/mailman/listinfo/python-list > -- http://mail.python.org/mailman/listinfo/python-list
