如何在Python中清晰展示内置异常层级结构？

Got it, let's break down how to properly visualize Python's built-in exception hierarchy (since dir(__builtins__) only gives you an alphabetical list with no inheritance context) and how to find all subclasses for any exception class.

1. Display the Full Exception Hierarchy #

Since BaseException is the root of all Python exceptions, we can build a recursive function to traverse its subclass tree and print them with indentation to clearly show the hierarchy:

def print_exception_hierarchy(cls, indent=0):
    # Print the current class with indentation matching its depth in the hierarchy
    print('  ' * indent + cls.__name__)
    # Recursively print all subclasses, sorted by name for readability
    for subclass in sorted(cls.__subclasses__(), key=lambda x: x.__name__):
        print_exception_hierarchy(subclass, indent + 1)

# Start traversal from the root exception class
print_exception_hierarchy(BaseException)

When you run this, you'll get a clean, indented tree showing exactly how exceptions inherit from each other. For example, you'll see Exception as a direct subclass of BaseException, then ArithmeticError under Exception, followed by ZeroDivisionError under ArithmeticError, and so on.

2. Find All Subclasses of a Specific Exception Class #

If you want to get all subclasses (including indirect ones) for a given exception class, use a recursive function to collect them:

Option 1: If you have the class object directly #

def get_all_subclasses(cls):
    subclasses = set()
    # Get direct subclasses first
    for subclass in cls.__subclasses__():
        subclasses.add(subclass)
        # Recursively add indirect subclasses
        subclasses.update(get_all_subclasses(subclass))
    return subclasses

# Example: Get all subclasses of Exception
all_exception_subclasses = get_all_subclasses(Exception)
# Print them sorted by name
for cls in sorted(all_exception_subclasses, key=lambda x: x.__name__):
    print(cls.__name__)

Option 2: If you only have the class name as a string #

First fetch the class from __builtins__, then use the same function:

class_name = "ValueError"
# Get the class object from built-ins
target_class = getattr(__builtins__, class_name)
# Get all its subclasses
all_subclasses = get_all_subclasses(target_class)
# Print results sorted by name
for cls in sorted(all_subclasses, key=lambda x: x.__name__):
    print(cls.__name__)

Bonus: Check the Inheritance Chain for a Single Class #

If you want to see the exact inheritance path for a specific exception (from the class up to BaseException), use inspect.getmro() (method resolution order):

import inspect
# Show the inheritance chain for ValueError
print(inspect.getmro(ValueError))
# Output: (ValueError, Exception, BaseException, object)

This tells you exactly which classes ValueError inherits from, top to bottom.

内容的提问来源于stack exchange，提问作者Billal BEGUERADJ