Jeff MudayTreehouse Moderator 23,332 Points
__name__ is a special variable in Python. The script file that is being directly executed will have the value of its
__name__ variable set to
The special signifcance of the variable is that it allows the program to make choices based on what module was executed at the top level.
If a script file is imported and you print the value of
__name__ it will have a different value. In fact, the value will match the name under which it is imported.
Here's a quick demo (note I am using Python 2.x, but Python 3.x will work the same except you will need parenthesis around the print arguments).
Suppose you have a single line Python file, called "script1.py"
print "executing script1 __name__ = " + __name__
When you execute it with the Python interpreter, it will print out the following.
executing script1 __name__ = __main__
So far so good...
Now let's create another script called "script2.py"
import script1 print "executing script2 __name__ = " + __name__
This will import script1, but you get something interesting.
executing script1 __name__ = script1 executing script2 __name__ = __main__
When script1 is imported it executes, but its special
__name__ is "script1". But then script2.py gets to its print statement and prints out that its special
This may seem confusing now, but you will see a repeating code pattern usually at the "bottom" of the execution module where the module checks if it's name is main and executes a code block. This is a good practice to implement and if you repeat it frequently it will become second nature!
if __name__ == '__main__': ... execute your code block here ...
Good luck with your Python journey!!