Test Your Knowledge: Answers

 

 
  1. The __init__.py file serves to declare and initialize a module package; Python automatically runs its code the first time you import through a directory in a process. Its assigned variables become the attributes of the module object created in memory to correspond to that directory. It is also not optional—you can’t import through a directory with package syntax unless it contains this file.
  2. Use the from statement with a package to copy names out of the package directly, or use the as extension with the import statement to rename the path to a shorter synonym. In both cases, the path is listed in only one place, in the from or import statement.
  3. Each directory listed in an import or from statement must contain an __init__.py file. Other directories, including the directory containing the leftmost component of a package path, do not need to include this file.
  4. You must use import instead of from with packages only if you need to access the same name defined in more than one path. With import, the path makes the references unique, but from allows only one version of any given name.
  5. from mypkg import spam is an absolute import—the search for mypkg skips the package directory and the module is located in an absolute directory in sys.path. A statement from . import spam, on the other hand, is a relative import—spam is looked up relative to the package in which this statement is contained before sys.path is searched.