第11章 调试

1. 抛出异常

• raise：抛出异常
• 只能在try代码块中抛出
• 不能像java让函数抛出异常

def calculate(i, j):
    if j == 0:
        raise Exception("Cannot calculate")

    print(i / j)


try:
    calculate(5, 0)
except Exception as e:
    print(str(e))
else:
    print("Finish")
1
2
3
4
5
6
7
8
9
10
11
12
13

2. 取得回溯字符串

• traceback.format_exc()：获取回溯信息

import traceback

try:
    raise Exception("Exception")
except Exception as e:
    print(traceback.format_exc())
1
2
3
4
5
6

3. 断言

• assert 布尔表达式：如果为 False 则回溯报错 AssertionError

nums = [1, 2, 3, 4, 5, 6, 7, 8, 9]
nums.reverse()
assert nums[0] <= nums[-1]
# 断言第一项小于最后一项
1
2
3
4

4. 日志

4.1 使用 logging 模块

• logging.basicConfig()：日志格式设置
• logging.debug()：调用logging.basicConfig()以输出信息

import logging

logging.basicConfig(
    level=logging.DEBUG,
    format='%(asctime)s - %(levelname)s - %(message)s')

logging.debug('Starting')


def test(n):
    logging.debug(f'Starting logging({n})')
    total = 1
    for i in range(1, n + 1):
        total *= i
        logging.debug(f"i = {i},total = {total}")
    logging.debug(f'Finished logging({n})')
    return total


print(test(5))
logging.debug('Finished')
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21

4.2 日志级别

4.3 禁用日志

• logging.disable() ：禁用在这行代码之后的所有信息

import logging

logging.basicConfig(
    level=logging.INFO,
    format='%(asctime)s - %(levelname)s - %(message)s')

logging.critical("Critical")

logging.disable(logging.CRITICAL)

logging.critical("Critical")
logging.error("Error")
1
2
3
4
5
6
7
8
9
10
11
12

4.4 将日志记录到文件

import logging

logging.basicConfig(
    filename="./logging.txt",
    level=logging.INFO,
    format='%(asctime)s - %(levelname)s - %(message)s')
logging.critical("Critical")
logging.critical("Critical")
logging.error("Error")
1
2
3
4
5
6
7
8
9