Re: import vs imp and friends.

[Emanuele D'Arrigo]

Christian, Robert, thank you both for the replies, much appreciated.

Manu
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import vs imp and friends.

[Emanuele D'Arrigo]

Greetings,

I was looking in the archive of this newsgroup and I found this
snippet:

import imp
sourcecode = 'def foo(x): return 11*x'
mod = imp.new_module('foo')
exec sourcecode in mod.__dict__
mod.foo(16)

Together with similar and sometimes more complete snippets available
they show how a module can be created out of string, plain text files
and compiled files. Neat!

Now the question. Apart from checking sys.module first and eventually
adding the new module to it if it isn't there already, and apart from
setting __file__, is there anything else that import does and this
snippet doesn't?

Manu
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Re: import vs imp and friends.

[Christian Heimes]

Emanuele D'Arrigo wrote:
 Now the question. Apart from checking sys.module first and eventually
 adding the new module to it if it isn't there already, and apart from
 setting __file__, is there anything else that import does and this
 snippet doesn't?

The import statement does several things. For instance it holds the
import lock to stop other threads from importing the same module again.
It also does lots of additional work for packages like relative imports,
checking __path__, setting attributes on parent packages and so on. The
import system also does a lot of work in order to find and load a
module, too.

Christian



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Re: import vs imp and friends.

[Robert Kern]

On 2009-07-23 09:44, Emanuele D'Arrigo wrote:

Greetings,

I was looking in the archive of this newsgroup and I found this
snippet:

import imp
sourcecode = 'def foo(x): return 11*x'
mod = imp.new_module('foo')
exec sourcecode in mod.__dict__
mod.foo(16)

Together with similar and sometimes more complete snippets available
they show how a module can be created out of string, plain text files
and compiled files. Neat!

Now the question. Apart from checking sys.module first and eventually
adding the new module to it if it isn't there already, and apart from
setting __file__, is there anything else that import does and this
snippet doesn't?


Brett Cannon has a good presentation that covers basically the entirety of the 
import mechanism:


http://us.pycon.org/2008/conference/schedule/event/12/

--
Robert Kern

I have come to believe that the whole world is an enigma, a harmless enigma
 that is made terrible by our own mad attempt to interpret it as though it had
 an underlying truth.
  -- Umberto Eco

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