Python进阶教程：调试技巧与性能优化

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import logging
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# 配置日志
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logging.basicConfig(
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    level=logging.DEBUG,
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    format="%(asctime)s %(levelname)s %(message)s",
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    filename="app.log",  # 输出到文件（可选）
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)
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logging.debug("调试信息")
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logging.info("普通信息")
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logging.warning("警告信息")
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logging.error("错误信息")
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logging.critical("严重错误")

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def divide(a, b):
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    assert b != 0, "除数不能为零"
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    return a / b
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divide(10, 0)  # AssertionError: 除数不能为零

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import pdb
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def process(data):
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    result = []
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    for item in data:
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        pdb.set_trace()  # 在此处暂停，进入调试模式
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        result.append(item * 2)
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    return result
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# process([1, 2, 3])
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# 调试器中常用命令：
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# n 下一步 | s 进入函数 | c 继续执行
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# p 变量名 打印变量 | q 退出

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import time
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start = time.perf_counter()
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total = sum(range(10**7))
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elapsed = time.perf_counter() - start
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print(f"耗时：{elapsed:.3f}s")

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import cProfile
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def slow_function():
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    total = 0
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    for i in range(10**6):
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        total += i ** 2
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    return total
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# 分析函数耗时
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cProfile.run("slow_function()")

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import time
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data = list(range(10**6))
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# 慢：Python 循环
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start = time.perf_counter()
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total = 0
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for x in data:
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    total += x
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print(f"循环：{time.perf_counter() - start:.4f}s")
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# 快：内置 sum
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start = time.perf_counter()
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total = sum(data)
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print(f"内置 sum：{time.perf_counter() - start:.4f}s")

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# 慢
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squares = []
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for i in range(1000):
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    squares.append(i * i)
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# 快（且更简洁）
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squares = [i * i for i in range(1000)]

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from functools import lru_cache
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@lru_cache(maxsize=128)
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def fibonacci(n):
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    if n < 2:
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        return n
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    return fibonacci(n-1) + fibonacci(n-2)
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print(fibonacci(100))  # 有缓存后瞬间返回

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# 列表：一次性全部加载到内存
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nums_list = [i for i in range(10**7)]
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# 生成器：按需生成，几乎不占内存
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nums_gen = (i for i in range(10**7))
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print(sum(nums_gen))  # 仍然可以求和

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def add(a: int, b: int) -> int:
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    """返回两个整数的和"""
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    return a + b
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# 类型注解提高可读性，配合 mypy 可静态检查

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import time
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from functools import lru_cache
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# 原始版本（慢）
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def count_primes_below(n):
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    primes = []
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    for num in range(2, n):
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        if all(num % p != 0 for p in primes):
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            primes.append(num)
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    return len(primes)
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# 优化版本（快）
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@lru_cache(maxsize=None)
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def optimized_count(n):
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    if n < 2:
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        return 0
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    sieve = [True] * n
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    sieve[0] = sieve[1] = False
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    for i in range(2, int(n ** 0.5) + 1):
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        if sieve[i]:
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            for j in range(i*i, n, i):
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                sieve[j] = False
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    return sum(sieve)
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start = time.perf_counter()
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print(f"慢版本：{count_primes_below(20000)} 个素数")
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print(f"耗时：{time.perf_counter() - start:.2f}s")
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start = time.perf_counter()
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print(f"快版本：{optimized_count(20000)} 个素数")
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print(f"耗时：{time.perf_counter() - start:.2f}s")