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from Versus import with Packages

import statements can be somewhat inconvenient to use with packages, because you may have to retype the paths frequently in your program. In the prior section’s example, for instance, you must retype and rerun the full path from dir1 each time you want to reach z. If you try to access dir2 or mod directly, you’ll get an error:

>>> dir2.mod
NameError: name 'dir2' is not defined
>>> mod.z
NameError: name 'mod' is not defined

It’s often more convenient, therefore, to use the from statement with packages to avoid retyping the paths at each access. Perhaps more importantly, if you ever restructure your directory tree, the from statement requires just one path update in your code, whereas imports may require many. The import as extension, discussed formally in the next chapter, can also help here by providing a shorter synonym for the full path:

% python
>>> from dir1.dir2 import mod      # Code path here only
dir1 init
dir2 init
in mod.py
>>> mod.z                          # Don't repeat path
3
>>> from dir1.dir2.mod import z
>>> z
3
>>> import dir1.dir2.mod as mod    # Use shorter name (see Chapter 24)
>>> mod.z
3