Jean-Michel Pichavant wrote:
lordofcode wrote:
Hi All
Not an expert in Python, so sorry if this sounds like a silly
question.
I went through other few threads in the mailing list but they are not
helping me much.
I have run into a problem related to dynamically loading and unloading
a module.
I need to dynamically load a module and unload it and load another
module.
For example I have many files(All files in Python are modules right?)
like mobile_1.py ,mobile_2.py, mobile_3.py etc.. in my project folder
which contains classes and methods with same name but different
functionality.(am afraid I cannot change this structure as these files
are generated randomly by the user)
So initially when my program starts I have to load a default module. I
do this as follows:
##############################
MODULE_name = "mobile_1"
exec "from "+MODULE_name+" import *"
##############################
And use the methods defined in "mobile_1.py" file
Now as the application continues , I may have to use the methods
defined in "mobile_2.py" or "mobile_3.py" etc instead of the
previously loaded module,which I incorrectly try to do as below:
####################
MODULE_name = "mobile_2"
exec "from "+MODULE_name+" import *"
#####################
The above import does not have any impact and the methods called from
my application still pertain to mobile_1.py as its still in the
current namespace(?).
I tried below code with del(), reload() etc but could not figure it
out.
###Code to unload a dll####
del sys.modules[MODULE_name] #==> does not delete the reference
in namespace
1)How do I unload a module dynamically and completely remove the
references in the module so a new module with same name references can
be loaded?
2)Are there any alternative way to do the above requirement?
Currently I am working around by restarting the whole initial setup
for each new module which is unnecessary waste.Can I avoid this
"reset"?
1/ Do not use from x import *
2/ How many modules would you like to import in the end ? If this
number is bound I would suggest to use a static approach:
import mod1
import mod2
import mod3
mod4 = __import__('mod4') # equivalent to import mod4
for mod in [mod1, mod2, mod3, mod4]:
# will call func1 on each modules
print "now using module %s functions " % mod.__file__
mod.func1()
mod.func2()
With this approach it's pretty much easy to call the correct
methods/attributes, as every symbols is scopped by module namespace.
You will have less hard time debugging your code.
3/ if you really need to unload the previous module, it's a little bit
tedious.
import mod1
del mod1
sys.modules['mod1'] = None # will unload mod1 assuming mod1 was the
only reference to that module.
But believe me, you don't want to mess up with the python import
mechanism.
JM
You may also want to look at the imp module,
http://docs.python.org/library/imp.html
It could help you in your task.
JM
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