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# Python singledispatch 泛型函数 —— 根据类型自动选择实现
# 替代 isinstance 链，实现类似"重载"的效果，代码更整洁

from functools import singledispatch, singledispatchmethod
from collections.abc import Iterable, Mapping, Sequence
import numbers

# 1. 单分派基础用法
@singledispatch
def format_value(value):
return f"未知类型: {type(value).__name__}"

@format_value.register(int)
def _(v): return f"整数: {v:,}"

@format_value.register(float)
def _(v): return f"浮点数: {v:.2f}"

@format_value.register(str)
def _(v): return f"字符串: '{v}'"

@format_value.register(list)
def _(v): return f"列表(len={len(v)}): {v[:3]}..."

@format_value.register(bool)
def _(v): return f"布尔: {'真' if v else '假'}"

@format_value.register(type(None))
def _(v): return "空: None"

for val in [1234567, 3.14159, "Hello", [1,2,3,4], True, None]:
print(format_value(val))

# 2. singledispatchmethod —— 方法级分派
class DataProcessor:
@singledispatchmethod
def process(self, data):
raise TypeError(f"不支持: {type(data).__name__}")

@process.register(int)
def _(self, data): return data * 2

@process.register(str)
def _(self, data): return data.upper()

@process.register(list)
def _(self, data): return [self.process(item) for item in data]

@process.register(dict)
def _(self, data): return {k: self.process(v) for k, v in data.items()}

p = DataProcessor()
print("\n方法分派:", p.process(42), p.process("hello"))
print("列表:", p.process([1, "a", 3]))

# 3. 基于 ABC 的分派
@singledispatch
def analyze(obj): return f"未知: {type(obj).__name__}"

@analyze.register(numbers.Integral)
def _(obj): return f"整型数: {'偶' if obj % 2 == 0 else '奇'}, 值={obj}"

@analyze.register(Iterable)
def _(o): return f"可迭代: {list(o)[:5]}..."

@analyze.register(Mapping)
def _(o): return f"映射: 键={list(o.keys())[:3]}"

print("\nABC分派:", analyze(42), analyze([1,2,3]), analyze({"a":1}))

# 4. 替代 isinstance 链
def process_old(v):
if isinstance(v, int): return v + 1
elif isinstance(v, str): return v[::-1]
elif isinstance(v, list): return len(v)
elif isinstance(v, dict): return sum(v.values())
else: return v

@singledispatch
def process_new(v): return v
@process_new.register(int)
def _(v): return v + 1
@process_new.register(str)
def _(v): return v[::-1]
@process_new.register(list)
def _(v): return len(v)
@process_new.register(dict)
def _(v): return sum(v.values())

for val in [42, "hello", [1,2,3], {"a":10,"b":20}, 3.14]:
print(f" {type(val).__name__}: 旧={process_old(val)}, 新={process_new(val)}")

# 5. 多个类型注册同一实现
def register_multiple(registry_func, *types):
def decorator(func):
for typ in types:
registry_func.register(typ)(func)
return func
return decorator

@singledispatch
def safe_convert(value): return value

@register_multiple(safe_convert, int, float)
def _(v): return float(v)

@register_multiple(safe_convert, str, bytes)
def _(v): return str(v).strip()

for val in [10, 3.14, " hello ", b"data"]:
print(f" {type(val).__name__:8} -> {safe_convert(val)!r}")