Documentation for importing modules / pythonpath?

[Steven Taschuk]

(Just replying to one piece of this.)

Quoth Johannes Eble:
  [...]
> Furthermore,
> I am used to the Java way to handle the import /classpath issue. I
> think the main difference is that Java doesn't have modules, it has
> only classes and packages (classes=files=modules if you like it that
> way). If you write 'import <package>' and the package is in your
> classpath then you can use all the classes of that package. In Python
> you have to write 'from <package>.A import A', 'from <package>.B
> import B' and so on for all (class) files in the package to get the
> same effect.  [...]

Following the Java way of doing things will be very inconvenient
in Python, as you are discovering.

In Java, you have, for example,
	java/
		util/
			LinkedList.java
			HashSet.java
			(etc., one file per class)
In Python you'd normally do this instead:
	java/
		util.py (one file, lots of classes)

Don't think of Java classes as being like Python modules just
because they both consist of a single source file -- that's
incidental.  Instead, think of Python modules as being like Java
packages:

  - Things in the same Python module can refer to each other without
    imports, just like classes in the same Java package can refer to
    each other without imports.

  - You can import all the things in a module at once with 'from foo
    import *', just like you can 'import java.util.*' in Java.

(Packages in Python are a bit like Java packages that have
subpackages.)

> [...] I think that Java is easier to use here if you write only
> one class in one file (which I definitely prefer).

Certainly Java makes things easier if you do things Java's way. 
But Java's way is not Python's.  (Neither is it C's way: imagine
putting each function in its own .c file and having to #include
"foo.h" for every function you wanted to use.  Ick.)

Why do you prefer having one class in one file?  (That always
annoyed me in Java.)

-- 
Steven Taschuk                               staschuk at telusplanet.net
"What I find most baffling about that song is that it was not a hit."
                            -- Tony Dylan Davis (CKUA)