Changes in Python 3.0

The way import operations in packages work has changed slightly in Python 3.0. This change applies only to imports within files located in the package directories we’ve been studying in this chapter; imports in other files work as before. For imports in packages, though, Python 3.0 introduces two changes:

 

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  • It modifies the module import search path semantics to skip the package’s own directory by default. Imports check only other components of the search path. These are known as “absolute” imports.
  • It extends the syntax of from statements to allow them to explicitly request that imports search the package’s directory only. This is known as “relative” import syntax.

These changes are fully present in Python 3.0. The new from statement relative syntax is also available in Python 2.6, but the default search path change must be enabled as an option. It’s currently scheduled to be added in the 2.7 release[53]—this change is being phased in this way because the search path portion is not backward compatible with earlier Pythons.

The impact of this change is that in 3.0 (and optionally in 2.6), you must generally use special from syntax to import modules located in the same package as the importer, unless you spell out a complete path from a package root. Without this syntax, your package is not automatically searched.