How Did PEP 404 Change Python\'s Import Statements?

Impact of PEP-404 on Python Import Statements

The Python Enhancement Proposal (PEP) 404 introduced significant changes to import statements in Python 3, enhancing the clarity and organization of module imports.

What is a Relative Import?

A relative import refers to importing a module from a location relative to the current module or package. In Python 2, implicit relative imports were allowed, but this has been restricted in Python 3.

Changes to Relative Imports

PEP-404 enforces explicit relative imports. Modules must now be imported using the leading . (dot) or .. (double dot) to specify the path relative to the current module's directory. For example:

from .mymodule import MyFunction  # Import from within the current package
from ..otherpackage import OtherClass  # Import from one level up in the directory structure

Restrictions on Star Imports

Star imports (importing all submodules and attributes from a package) are now only permitted at module level code. Previously, star imports were allowed in function and class definitions, but this has been prohibited to prevent namespace pollution and unexpected behavior.

Example:

Python 2 code:

# Function-level star import
def my_function():
    from mymodule import *
    do_something_with(MyAttribute)

# Class-level star import
class MyClass:
    def __init__(self):
        from otherpackage import *
        self.other_variable = OtherVariable

Python 3 code:

# Module-level star import
import mymodule
do_something_with(mymodule.MyAttribute)

# Explicit import within function
def my_function():
    from mymodule import MyAttribute
    do_something_with(MyAttribute)

# Explicit import within class
class MyClass:
    def __init__(self):
        from otherpackage import OtherVariable
        self.other_variable = OtherVariable

By enforcing explicit imports and restricting star imports, Python 3 aims to improve import clarity, reduce namespace collisions, and promote a more structured and maintainable codebase.

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