This happens because the scipy module doesn't have any attribute named sparse. That attribute only gets defined when you import scipy.sparse.

Submodules don't automatically get imported when you just import scipy; you need to import them explicitly. The same holds for most packages, although a package can choose to import its own submodules if it wants to. (For example, if scipy/__init__.py included a statement import scipy.sparse, then the sparse submodule would be imported whenever you import scipy.)

You are giving the object.__getattribute__() handler a signal that the attribute doesn't exist by raising an AttributeError. The defined behaviour is to then call __getattr__ instead. The exception is lost, it was handled by __getattribute__. From the documentation:

Called unconditionally to implement attribute accesses for instances of the class. If the class also defines __getattr__(), the latter will not be called unless __getattribute__() either calls it explicitly or raises an AttributeError.

If you don't want __getattribute__ to handle the exception, you need to move your __getattr__ behaviour over to a custom __getattribute__ method instead:

class A(object):
    @property
    def test(self):
        raise AttributeError('message which should not be lost')
        return 'this would never return'

    def __getattribute__(self, name):
        try:
            value = super(A, self).__getattribute__(name)
        except AttributeError as ae:
            # chance to handle the attribute differently
            # if not, re-raise the exception
            raise ae

Note that the hasattr() function behaves the same way; it'll return False when an exception is raised when trying to access the attribute.

Your constructor sets self.prevNode to None, and later you try to access node.prevNode.label, which is like trying to access None.label. None doesn't have any attributes, so trying to access any will give you an AttributeError.

And what does that error generally mean?

An Attribute in Python is a name belonging to an object - a method or a variable. An AttributeError means that the program tried to use an attribute of an object, but the object did not have the requested attribute.

For instance, string objects have the 'upper' attribute, which is a method that returns the uppercase version of the string. You could write a method that uses it like this:

def get_upper(my_string):
  return my_string.upper()

However, note that there's nothing in that method to ensure that you have to give it a string. You could pass in a file object, or a number. Neither of those have the 'upper' attribute, and Python will raise an Attribute Error.

As for why you're seeing it in this instance, you haven't provided enough detail for us to work it out. Add the full error message to your question.

I'm curious... how much do you know about scope in Python?

In your class, you have a member variable named x and another named y. Your init function accepts an argument called point0 and another called point1. It saves point0 in the x member variable, and point1 in y. Then, in your rotate function, you attempt to access a variable called point0. Do you see the problem?

An important thing to understand when programming (and this is true in most programming languages, if not all of them) is that the name of an argument doesn't affect the name of that data elsewhere. I can pass a variable called foo into a function that takes an argument called bar. In that function, I have to refer to the data as bar because that's the name of the variable. Later, after I've called that function, the name of the variable is still foo, because only the variable inside the function is called bar. Does that make sense?

AttributeError typically identifies the missing attribute. e.g.:

class Foo:
    def __init__(self):
        self.a = 1

f = Foo()
print(f.a)
print(f.b)

When I run that, I see:

$ python foo.py
1
Traceback (most recent call last):
  File "foo.py", line 10, in <module>
    print(f.b)
AttributeError: Foo instance has no attribute 'b'

That's pretty explicit. If you're not seeing something like that, please post the exact error you're seeing.

EDIT

If you need to force the printing of an exception (for whatever reason), you can do this:

import traceback

try:
    # call function that gets AttributeError
except AttributeError:
    traceback.print_exc()

That should give you the full error message and traceback associated with the exception.

self.entbx is created by create_widget(). You are calling reveal() -- which requires self.entbx -- before you've called create_widget():

self.reveal()
self.create_widget()

More code would be appreciated (specifically the ParamExample implementation), but I'm assuming you're missing the __enter__ (and probably __exit__) method on that class.

When you use a with block in python, the object in the with statement gets its __enter__ method called, the block inside the with runs, and then the __exit__ gets called (optionally with exception info if one was raised). Thus, if you don't have an __enter__ defined on your class, you'll see this error.

Side note: you need to either indent the second with block so it's actually inside the first, OR replace these two lines with

with ParamExample(URI) as pe, MotionCommander(pe, default_height=0.3) as mc:

which is the same as nesting these two context managers (the name of the objects used by with blocks).

Your indentation is goofed, and you've mixed tabs and spaces. Run the script with python -tt to verify.

Here:

File "/Users/name/anaconda/lib/python3.6/http/client.py", line 71, in <module>
    import email.parser
File "/Users/name/Desktop/Google Drive/FEBB/serverless/crwlr/email.py"
    from bs4 import BeautifulSoup

The local email.py in /Users/name/Desktop/Google Drive/FEBB/serverless/crwlr/ shadows the stdlib's one. Now in your local email.py module, you're importing bs4, which imports html5lib, which imports xml.sax.saxutils, which imports urllib.request, which wants to import http.

IOW you end up with an (accidental) circular dependencie. At this point the http module is only partially imported, and doesn't yet have defined "client", hence the error.

The simple solution is to rename your "email.py" module to something else, or (if it's only a script and not a module) move it out of your pythonpath.

EDIT: I just noticed that your code started by importing http, so the http module should be already fully loaded, so even if the problem with your email.py script/module needs to be fixed, this shouldn't lead to this problem. So chances are you have another http.py module or http package in your sys.path shadowing the stdlib's one. To debug this, add this line just after the import http one:

 print(http)

This should print something like:

<module 'http' from '/some/path/to/a/python/file.pyc`>

If the path is not the one to your python install stdlib's "http/init.pyc" then you found the offender. If it's one of your own scripts/modules, the fix is the same as for email.py.

You need two underscores before and after the init function: __init__. _init_ has no special meaning and isn't being called when your object is constructed.