[Tutor] Tutor FAQ

[Kent Johnson]

Mike Hansen wrote:
> ---------------------------------------------------------------------
> What's the difference between "import foo" and "from foo import *"?
> 
> import sys
> 
> This brings the *name* "sys" into your module.
(Technically, it binds the name "sys" to the object that is the sys module.)
> It does not give you access to any of the names inside sys itself (such 
> as

does not give you _direct_ access...
> exit for example). To access those you need to prefix them with sys, as 
> in
> 
> sys.exit()
> 
> from sys import *
> 
> This does NOT bring the name "sys" into your module, instead it brings 
> all
> of the names inside sys(like exit for example) into your module. Now 
> you can
> access those names without a prefix, like this:
> 
> exit()
> 
> So why not do that instead of
> 
> import sys?
> 
> The reason is that the second form will overwrite and names you have 
> already
> declared - like exit say.
> exit = 42
> from sys import *   # hides my exit variable.
> 
> OR more likely, the other way round
> 
> from sys import *
> exit = 42   # now hides the sys.exit function so I can't use it.
> 
> Of course some of these are obvious but there can be a lot of names in a
> module, and some modules have the same name in them, for example:
> 
> from os import *
> from urllib import *
> 
> open(foo)   # which open gets called, os.open or urllib.open?
> 
> Can you see how it gets confusing.
confusing?

Another disadvantage of "from sys import *" is that it makes it harder 
to find the definition of a name. If you see "sys.exit()" in the code, 
you know exactly where exit() is defined. If you see "exit()" in a 
module that has several "from xx import *" statements, you will have to 
search each imported module for the definition of exit().

> Bottom line is it is usually better to accept the extra typing and use
The bottom line...
> 
> import foo
> 
> or for just a few names
> 
> from foo import bar,baz
> 
> [from a post on Python Tutor by Alan Gauld]
> 
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