question on "import __main__"

[wen]

i have written some code in test.py as below:
import __main__
if __name__!='__main__':
print 1

print 2

when i run test.py, i got
2
on the screen.

now, i have some question about the code, 1. since no __main__ module at
all, why it's legal to write "import __main__"?

2. since if running a script independently, the __name__ should be
'__main__', why it's not in the above code?


thank you in advance.

with my kind regards,
Wen

 

[Robert Kern]

i have written some code in test.py as below:
import __main__
if __name__!='__main__':
print 1

print 2

when i run test.py, i got
2
on the screen.

now, i have some question about the code, 1. since no __main__ module at
all, why it's legal to write "import __main__"?

Because a module object is created for the running script. It is placed
in sys.modules with the name "__main__". When you "import __main__", the
import mechanism looks in sys.modules first for a module with the name
"__main__" and uses that if it's there.

2. since if running a script independently, the __name__ should be
'__main__', why it's not in the above code?

It is. However, you wrote "!=" instead of "==".

--
Robert Kern
(e-mail address removed)

"In the fields of hell where the grass grows high
Are the graves of dreams allowed to die."
-- Richard Harter

 

[infidel]

import __main__

if __name__!='__main__':
print 1

print 2

when i run test.py, i got
2
on the screen.

now, i have some question about the code, 1. since no __main__ module at
all, why it's legal to write "import __main__"?

__main__ is the module that the interpreter starts executing. So
"import __main__" is legal, though I'm guessing it doesn't really do
anything because the module is already loaded (since it's running).

2. since if running a script independently, the __name__ should be
'__main__', why it's not in the above code?

But it is.