Python 装饰器专项练习：6 道编程题从入门到精通

配套专栏：Python 全栈修炼之路 第 14 篇《装饰器——Python 最优雅的语法糖》

难度分布：⭐ → ⭐⭐ → ⭐⭐ → ⭐⭐⭐ → ⭐⭐⭐ → ⭐⭐⭐⭐

核心覆盖：闭包、@wraps、带参数装饰器、类装饰器、多层装饰器叠加、缓存/重试/权限实战

前言

装饰器是 Python 中最强大的语法特性之一，它让我们在不修改原函数代码的前提下，优雅地为函数添加额外功能。本练习精选 6 道编程题，从闭包基础到综合实战，帮你彻底掌握装饰器的精髓。

题目一：闭包计数器与计时器 ⭐

📌 题目描述

利用闭包实现一个函数调用计数器和一个简易计时器：

# 闭包计数器
counter = make_counter()
print(counter()) # 1
print(counter()) # 2
print(counter()) # 3
print(counter.count) # 3（查看当前计数）

# 每个计数器独立
counter_b = make_counter()
print(counter_b()) # 1
print(counter()) # 4（互不影响）

# 闭包计时器
timer = make_timer()
timer.start()
time.sleep(0.1)
print(timer.elapsed()) # ≈ 0.1 秒

💡 编程思路

这道题考察 闭包三大要素：嵌套函数、引用外部变量、返回内部函数。

🖥️ 参考代码

import time
from functools import wraps

def make_counter(initial: int = 0):
\”\”\”创建一个独立的计数器闭包。\”\”\”
count = initial

def counter():
nonlocal count
count += 1
return count

# 附加属性
counter.count = count
counter.reset = lambda: _reset()

def _reset():
nonlocal count
count = initial
counter.count = count

return counter

def make_timer():
\”\”\”创建一个计时器闭包。\”\”\”
start_time = None
elapsed_time = 0

def timer():
nonlocal start_time, elapsed_time

timer.start = lambda: _start()
timer.stop = lambda: _stop()
timer.elapsed = lambda: _elapsed()
timer.reset = lambda: _reset()

def _start():
nonlocal start_time
start_time = time.perf_counter()

def _stop():
nonlocal elapsed_time
if start_time is not None:
elapsed_time += time.perf_counter() – start_time
start_time = None

def _elapsed():
nonlocal elapsed_time
total = elapsed_time
if start_time is not None:
total += time.perf_counter() – start_time
return total

def _reset():
nonlocal start_time, elapsed_time
start_time = None
elapsed_time = 0

return timer

def make_averager():
\”\”\”创建一个运行平均值计算器。\”\”\”
numbers = []
total = 0

def averager(value=None):
nonlocal total
if value is not None:
numbers.append(value)
total += value
return total / len(numbers) if numbers else 0

averager.values = lambda: list(numbers)
averager.count = lambda: len(numbers)
return averager

# 测试
if __name__ == \”__main__\”:
print(\”=== 闭包计数器 ===\”)
c1 = make_counter()
print(f\”调用: {

c1()}\”) # 1
print(f\”调用: {

c1()}\”) # 2
print(f\”调用: {

c1()}\”) # 3

c2 = make_counter(10)
print(f\”独立计数器: {

c2()}\”) # 11
print(f\”原计数器: {

c1()}\”) # 4

c1.reset()
print(f\”重置后: {

c1()}\”) # 1

print(\”\\n=== 闭包计时器 ===\”)
t = make_timer()
t.start()
time.sleep(0.05)
print(f\”阶段1耗时: {

t.elapsed():.4f}s\”)
t.stop()
time.sleep(0.05)
t.start()
time.sleep(0.05)
t.stop()
print(f\”总耗时: {

t.elapsed():.4f}s\”)
t.reset()
print(f\”重置后: {

t.elapsed():.4f}s\”)

print(\”\\n=== 运行平均值 ===\”)
avg = make_averager()
avg(10)
avg(20)
avg(30)
print(f\”平均值: {

avg():.1f}\”)
print(f\”数据量: {

avg.count()}\”)

print(\”\\n所有测试通过 ✓\”)

🔗 关联知识点

题目二：日志记录装饰器 ⭐⭐

📌 题目描述

实现一个通用的日志记录装饰器，记录函数调用信息：

@log_call
def add(a, b):
return a + b

add(3, 5)
# [CALL] add(3, 5)
# [RETURN] add → 8

@log_call(level=\”DEBUG\”)
def greet(name, greeting=\”Hello\”):
return f\”{

greeting}, {

name}!\”

greet(\”Alice\”, greeting=\”Hi\”)
# [DEBUG] greet(name=\’Alice\’, greeting=\’Hi\’)
# [DEBUG] greet → \’Hi, Alice!\’

# 验证元信息保留
print(add.__name__) # add（不是 wrapper）
print(greet.__doc__) # 原文档字符串

💡 编程思路

这道题考察 基础装饰器 + @wraps + *args/**kwargs：

🖥️ 参考代码

import time
import functools
from datetime import datetime

def log_call(func):
\”\”\”记录函数调用信息的装饰器。\”\”\”

@functools.wraps(func)
def wrapper(*args, **kwargs):
# 构建参数字符串
args_str = \”, \”.join(repr(a) for a in args)
kwargs_str = \”, \”.join(f\”{

k}={

v!r}\” for k, v in kwargs.items())
all_args = \”, \”.join(filter(None, [args_str, kwargs_str]))

print(f\”[CALL] {

func.__name__}({

all_args})\”)

start = time.perf_counter()
result = func(*args, **kwargs)
elapsed = time.perf_counter() – start

print(f\”[RETURN] {

func.__name__} → {

result!r} ({

elapsed:.6f}s)\”)
return result

return wrapper

def log_with_level(level=\”INFO\”):
\”\”\”带日志级别的装饰器工厂。\”\”\”

def decorator(func):
@functools.wraps(func)
def wrapper(*args, **kwargs):
args_str = \”, \”.join(
f\”{

a!r}\” for a in args
) + (\”, \” if kwargs else \”\”) + \”, \”.join(
f\”{

k}={

v!r}\” for k, v in kwargs.items()
)
ts = datetime.now().strftime(\”%H:%M:%S\”)
print(f\”[{

level}] {

ts} {

func.__name__}({

args_str})\”)

result = func(*args, **kwargs)

print(f\”[{

level}] {

ts} {

func.__name__} → {

result!r}\”)
return result

return wrapper
return decorator

def log_to_file(filepath: str):
\”\”\”将日志写入文件的装饰器。\”\”\”

def decorator(func):
@functools.wraps(func)
def wrapper(*args, **kwargs):
args_str = \”, \”.join(f\”{

a!r}\” for a in args)
kwargs_str = \”, \”.join(f\”{

k}={

v!r}\” for k, v in kwargs.items())
all_args = \”, \”.join(filter(None, [args_str, kwargs_str]))

result = func(*args, **kwargs)

log_line = (
f\”[{

datetime.now().isoformat()}] \”
f\”{

func.__name__}({

all_args}) → {

result!r}\\n\”
)
with open(filepath, \”a\”, encoding=\”utf-8\”) as f:
f.write(log_line)

return result
return wrapper
return decorator

# 测试
if __name__ == \”__main__\”:
print(\”=== log_call ===\”)