Creating an object from a string, is it possible?

Question

Is it possible to do the following

This works

usethismodule.LoginUsername="my value"
usethismodule.LoginPassword="another value"

But I don't know the second part of the object until the code is being run, I think what I want is this

listofthings=[]
listofthings.append('usethismodule.LoginUsername')
listofthings.append('usethismodule.LoginPassword')

for value in listofthings:
    value="A value I set"

This would have the same outcome as the above. Does that make sense?

You might want `setattr`, for example, `setattr(usethismodule, 'LoginUsename', "my value")` — chepner, Mar 03 '17 at 15:12
Possible duplicate of [Using a string variable as a variable name](http://stackoverflow.com/q/11553721/953482). Short answer: use a dict. — Kevin, Mar 03 '17 at 15:13

linusg · Accepted Answer · 2017-03-14T09:24:51.357

2

Indeed, setattr and a dictionary would do the trick.

dictofthings = {
    'usethismodule.LoginUsername': 'my value',
    'usethismodule.LoginPassword': 'my other value'
}

for k in dictofthings:
    setattr(eval(k.split('.')[0]), k.split('.')[1], dictofthings[k])

Hope this helps!

edited Mar 14 '17 at 09:24

answered Mar 03 '17 at 15:17

linusg

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But the module name is part of the data as well. You made it part of the code. – Stefan Pochmann Mar 03 '17 at 15:27
OK, changed. Note that eval *may* be a security hole, but `ast.literal_eval` won't work. Is this better? – linusg Mar 03 '17 at 15:30
I'd say it's better because that's what they apparently want, but worse because of that eval security issue :-). Maybe a mix of your answer and Austin's answer (which assumes a single module name) would be best. – Stefan Pochmann Mar 03 '17 at 15:35

score 0 · Answer 2 · answered Mar 03 '17 at 15:25

You keep saying usethismodule.<something>. So let's pretend you're right.

Python maintains a dict of currently imported modules in sys.modules. You can look up a module, by name, and get an "object". (A module object, in fact.)

If you have an object in hand, you can either hard-code an access to one of its attributes, or use getattr or setattr on it.

import sys

module_name = "usethismodule"   # I don't know where this come from.

utm = sys.modules[module_name]

utm.LoginUsername = "xyzzy"
utm.LoginPassword = "secret123"

# or

pw_attr_name = "passWord"       # Maybe you read this from a config file?
setattr(utm, pw_attr_name, "secret123")

Creating an object from a string, is it possible?

2 Answers2