Python Forum

Hello, I want to import modules from files, I need to store them into variables and I need their names as strings because I must check if the modules python files exist or not for example.
My question is, how to assign a module to a variable even if it's not defined? See the line 1 below, thanks.

module = math # NameError: name 'math' is not defined
module_str = module.__name__ # It should be 'math', but not 'module' because it's not a variable name.
import module

To make everything clear, here is another example, I want to store the string 'math' into a variable, then I import it:

import 'math' # SyntaxError: invalid syntax

This looks very much like XY problem. Would you elaborate on what the ultimate goal is? "check if the modules python files exist or not" is not very clear.

e.g. if you want to check that trying to import module will not raise error - there is idiomatic way to do it using try/except

if you want to import module by using name string - look at importlib

New question: "How to create a module or variable with the name from a string?"

import sys
import os
import importlib

dir = os.path.dirname(bpy.data.filepath)
dir = os.path.join(dir, "Scripts") # The script must be located in that folder
if not dir in sys.path:
    sys.path.append(dir)
'''
#---------- Method 1 ----------
# There is no problem if there is no 'for', but I will have many modules, so I can't do these.
main = importlib.import_module('main')
MyModule = importlib.import_module('MyModule')'''

#---------- Method 2 ----------
module_names = (
    'main',
    'MyModule')

for name in module_names:
    value = importlib.import_module(name)
    create_var_by_str(name, value) # FIXME: Here is my problem, I want to create a variable named of the
                                   # value of 'name', and assign to it the value of 'value'.

again, why are you doing all this?

I'm sorry.
The terms say that I come back if I find the solution. I use 'exec' to create a variable from string.

>>> exec("abc = 123")
>>> abc
123

Bye, I will make effort next time, I will try to be perfect.

(Aug-12-2020, 03:16 PM)mandaxyz Wrote: [ -> ]The terms say that I come back if I find the solution. I use 'exec' to create a variable from string.

Yes,but a better way could be to use a data structure like dictionary.
What's really happens when do exec("abc=123") or just abc = 123,is that Python map this to a internal global dictionary.

>>> exec("abc = 123")
>>> globals()['abc']
123
>>> type(globals())
<class 'dict'>

So the way to make this more clear is to use real visible dictionary.

>>> d = dict(abc=123, foo=456)
>>> d
{'abc': 123, 'foo': 456}
>>> d['abc']
123

# Then also get method like get
>>> d.get('abc', 'Not in record')
123
>>> d.get('abcd', 'Not in record')
'Not in record'
>>> d.get('foo', 'Not in record')
456

mandaxyz Wrote:Bye, I will make effort next time, I will try to be perfect

To be perfect is a goal we all will fail at
I think just a little expatiation of the goal of doing this was the point here.