Python * imports

Question

I've generally been told that the following is bad practice.

from module import *

The main reasoning (or so I've been told), is that you could possibly import something you didn't want, and it could shadow a similarly named function or class from another module.

However, what about PyQt

from PyQt4.QtCore import *

Every example I've ever seen is written this way, mainly because everything exported from Qt starts with "Q", so it's not going to shadow anything.

What's the concensus? Is it always bad to use * imports?

EDIT:

Just to be clear, this question is specifically in regards to using PyQt4. It has nothing to do with the way I am designing some other project.

Basically, I've found that coding to PEP8 has improved my code readability, except with regards to importing PyQt4, and so I've disregarded the frowns from purists until now. But now my dev group is deciding on one convention and I'm wondering if this is a scenario "where practicality beats purity", or if I should just suck it up and deal with monstrous PyQt4 imports

from PyQt4.QtGui import QComboBox, QLineEdit, QLayout, Q;lakdfaf.......

Answer 1

The PyQt design is water under the bridge. I'm not sure it's the best thing, but it's probably influenced by the way Qt was designed. AFAIK, Qt didn't use C++ namespaces historically (I'm not sure if it uses them now), and therefore had to use prefixes. But all of those design decisions probably happened more than 10 years ago, and that shouldn't affect your design decisions now.

I know that if I was designing a library now, I would definitely choose to use package namespaces (which you would import explicitly in Python) over prefixes. Let's say my prefix is Pfx - if the library user doesn't care writing PfxFunc() every time he needs a function, he certainly wouldn't care about the extra character in Pfx.Func(), especially when he can use import with specific symbol names to shorten that even more.

Answer 2

Consider this case

from foo import *
from bar import *

x=baz()

Now suppose foo has a function called baz() that we are using in our code and everything is working fine. Months or years pass, the author of bar adds a function called baz(). Someone updates the egg ang bingo - we have a potentially hard to detect bug in the program.

Not to mention that just looking at those three lines of code, I can't tell where baz comes from without going and looking at foo and bar

The only time I'd use import * would be in the interpreter to save some typing