## The `import` statement

    import_stmt     ::=  "import" module ["as" name] ( "," module ["as" name] )*
                         | "from" relative_module "import" identifier ["as" name]
                         ( "," identifier ["as" name] )*
                         | "from" relative_module "import" "(" identifier ["as" name]
                         ( "," identifier ["as" name] )* [","] ")"
                         | "from" module "import" "*"
    module          ::=  (identifier ".")* identifier
    relative_module ::=  "."* module | "."+
    name            ::=  identifier

The basic import statement (no `from` clause) is executed in two steps:

1. find a module, loading and initializing it if necessary
2. define a name or names in the local namespace for the scope where the `import` statement occurs.

When the statement contains multiple clauses (separated by commas) the two steps are carried out separately for each clause, just as though the clauses had been separated out into individiual import statements.

The details of the first step, finding and loading modules are described in greater detail in the section on the import system, which also describes the various types of packages and modules that can be imported, as well as all the hooks that can be used to customize the import system. Note that failures in this step may indicate either that the module could not be located, or that an error occurred while initializing the module, which includes execution of the module’s code.

If the requested module is retrieved successfully, it will be made available in the local namespace in one of three ways:

- If the module name is followed by `as`, then the name following `as` is bound directly to the imported module.
- If no other name is specified, and the module being imported is a top level module, the module’s name is bound in the local namespace as a reference to the imported module
- If the module being imported is not a top level module, then the name of the top level package that contains the module is bound in the local namespace as a reference to the top level package. The imported module must be accessed using its full qualified name rather than directly

The `from` form uses a slightly more complex process:

1. find the module specified in the `from` clause, loading and initializing it if necessary;
2. for each of the identifiers specified in the `import` clauses:
   1. check if the imported module has an attribute by that name
   2. if not, attempt to import a submodule with that name and then check the imported module again for that attribute
   3. if the attribute is not found, `ImportError` is raised.
   4. otherwise, a reference to that value is stored in the local namespace, using the name in the `as` clause if it is present, otherwise using the attribute name

Examples:

    import foo                 # foo imported and bound locally
    import foo.bar.baz         # foo.bar.baz imported, foo bound locally
    import foo.bar.baz as fbb  # foo.bar.baz imported and bound as fbb
    from foo.bar import baz    # foo.bar.baz imported and bound as baz
    from foo import attr       # foo imported and foo.attr bound as attr

If the list of identifiers is replaced by a star (`'*'`), all public names defined in the module are bound in the local namespace for the scope where the `import` statement occurs.

The public names defined by a module are determined by checking the module’s namespace for a variable named `__all__`; if defined, it must be a sequence of strings which are names defined or imported by that module. The names given in `__all__` are all considered public and are required to exist. If `__all__` is not defined, the set of public names includes all names found in the module’s namespace which do not begin with an underscore character (`'_'`). `__all__` should contain the entire public API. It is intended to avoid accidentally exporting items that are not part of the API (such as library modules which were imported and used within the module).

The wild card form of import — `from module import *` — is only allowed at the module level. Attempting to use it in class or function definitions will raise a `SyntaxError`.

When specifying what module to import you do not have to specify the absolute name of the module. When a module or package is contained within another package it is possible to make a relative import within the same top package without having to mention the package name. By using leading dots in the specified module or package after `from` you can specify how high to traverse up the current package hierarchy without specifying exact names. One leading dot means the current package where the module making the import exists. Two dots means up one package level. Three dots is up two levels, etc. So if you execute `from . import mod` from a module in the `pkg` package then you will end up importing `pkg.mod`. If you execute `from ..subpkg2 import mod` from within `pkg.subpkg1` you will import `pkg.subpkg2.mod`. The specification for relative imports is contained within PEP 328.

`importlib.import_module()` is provided to support applications that determine dynamically the modules to be loaded.