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POGetting 'has no attribute' error using __import__
 

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  1. POGetting 'has no attribute' error using __import__
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    <p>I've run across a strange issue, and I have not found any similar issues in my searches; which probably means the issue is plainly obvious and I am just not seeing it. I have a class module called modulefile.py, in a folder called modulefolder. Here is modulefile.py:</p> <pre><code>class moduleclass(object): def __init__(self): self.parameter = 5 </code></pre> <p>Now, in my test1.py file I do this:</p> <pre><code>from modulefolder.modulefile import moduleclass myobj = moduleclass() print myobj.parameter </code></pre> <p>And this works great - it prints the value 5 as expected.</p> <p>Now, my problem is that in my application I won't know modulefolder, modulefile and moduleclass until runtime. They will be provided to me in strings. So I tried this, this is test2.py:</p> <pre><code>module = __import__("modulefolder.modulefile", fromlist=["moduleclass"]) myobj = getattr(module, "moduleclass") print myobj.parameter </code></pre> <p>And this doesn't work, I get an error <code>AttributeError: type object 'moduleclass' has no attribute 'parameter'</code>.</p> <p>So, this is what is baffling me. In both test1.py and test2.py I changed the print statment to <code>print dir(myobj)</code> instead, and I get this:</p> <p>For test1.py:</p> <pre><code>['__class__', '__delattr__', '__dict__', '__doc__', '__format__', '__getattribute__', '__hash__', '__init__', '__module__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__setattr__', '__sizeof__', '__str__', '__subclasshook__', '__weakref__', 'parameter'] </code></pre> <p>For test2.py</p> <pre><code>['__class__', '__delattr__', '__dict__', '__doc__', '__format__', '__getattribute__', '__hash__', '__init__', '__module__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__setattr__', '__sizeof__', '__str__', '__subclasshook__', '__weakref__'] </code></pre> <p>So, clearly, the second import method is missing my 'parameter' attribute. The problem is, I don't know why. </p> <p>Why does this method of dynamic import affect the way the instantiated object works? And what can I do to fix it?</p> <p>I've searched high-and-low looking for answers, so it's probably something straightforward that I've overlooked, or just don't fully understand.</p>
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    1. USRaceyman
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    1. COAny reason you are not using the [`importlib` module](http://docs.python.org/2/library/importlib.html) instead?
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      1. POGetting 'has no attribute' error using __import__
      1. USMartijn Pieters
    2. CO`myobj = getattr(module, "moduleclass")` returns the class, not an instance. try: `myobj = getattr(module, "moduleclass")()`
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      1. USshx2
    3. CO@MP - you see, I was having the same problem with importlib. This should fix that too.
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      1. POGetting 'has no attribute' error using __import__
      1. USRaceyman
 

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