Programming Forums > Script Programming > Python

Dietrich · Dec 28th, 2006, 12:25 PM

I usually import all the needed modules in the beginning of my program. I keep seeing code that imports modules within a function, wouldn't that be bad? I assume that the module will be imported every time the function is called.

BinarySurfer · Dec 28th, 2006, 12:52 PM

I've done it before without any problems, though I would avoid importing the randomizer in a function. The module would be loaded at the beginning of the function (or where ever) and dropped at the end, so it's I think it's okey. I don't recommend doing it that way because it hurts performance if that function is used often. I would do it in a function that's not used often, otherwise I would import it at the beginning of the code like usual.

Arevos · Dec 28th, 2006, 1:41 PM

Quote:

Originally Posted by Dietrich

I usually import all the needed modules in the beginning of my program. I keep seeing code that imports modules within a function, wouldn't that be bad? I assume that the module will be imported every time the function is called.

Modules are cached in memory, so they are only ever imported once. This can be tested via the following code:

 python Syntax (Toggle Plain Text) 
def foo():
	import string
	string.test = "Hello"
	print string.test
 
def bar():
	import string
	print string.test
 
foo()
bar()
def foo():
	import string
	string.test = "Hello"
	print string.test

def bar():
	import string
	print string.test

foo()
bar()

However, even though modules are cached, there's still some overhead in searching the cache for the module. So although it doesn't make much difference, it still results in slight performance degradation

titaniumdecoy · Dec 28th, 2006, 5:10 PM

Quote:

Originally Posted by Arevos

However, even though modules are cached, there's still some overhead in searching the cache for the module. So although it doesn't make much difference, it still results in slight performance degradation

Wouldn't the cache have to be searched either way?

Game_Ender · Dec 29th, 2006, 2:21 AM

It will only get searched once you import the module at file scope. It will be searched every time you run the function if you import inside the function.

Arevos · Dec 29th, 2006, 5:47 AM

Quote:

Originally Posted by titaniumdecoy

Wouldn't the cache have to be searched either way?

As I understand it, if it's already imported, only the namespace must be searched for the module name. If it's imported in the middle of the function, first the module cache has to be searched (in order to import the module into the current namespace), and then the namespace.

Dec 28th, 2006, 12:25 PM	#1
Dietrich Professional Programmer Join Date: Feb 2005 Posts: 434 Rep Power: 4	Import a Module I usually import all the needed modules in the beginning of my program. I keep seeing code that imports modules within a function, wouldn't that be bad? I assume that the module will be imported every time the function is called. __________________ I looked it up on the Intergnats!

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Dec 28th, 2006, 12:52 PM	#2
BinarySurfer Programmer Join Date: Dec 2006 Posts: 53 Rep Power: 0	I've done it before without any problems, though I would avoid importing the randomizer in a function. The module would be loaded at the beginning of the function (or where ever) and dropped at the end, so it's I think it's okey. I don't recommend doing it that way because it hurts performance if that function is used often. I would do it in a function that's not used often, otherwise I would import it at the beginning of the code like usual.

Dec 29th, 2006, 2:21 AM	#5
Game_Ender Professional Programmer Join Date: May 2006 Location: Maryland, USA Posts: 306 Rep Power: 3	It will only get searched once you import the module at file scope. It will be searched every time you run the function if you import inside the function.

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Programming Forums > Script Programming > Python

Import a Module