Python代码调试工具PySnooper

秦羽 2021-12-20 AM 319℃ 0条

## 介绍

PySnooper工具使用采用装饰器的形式，将函数的运行过程以日志的形式打印到文件中，其记录了运行了哪些代码行，运行的时间及运行到当前代码时各变量的值。根据变量的变化就可以定位问题了。亲自试用该工具后，其优点可总结为以下几点：

- 无需为了查看变量的值，使用print打印变量的值，从而修改了原有的代码。
- 接口的运行过程以日志的形式保存，方便随时查看。
- 可以根据需要，设置函数调用的函数的层数，方便将注意力集中在需要重点关注的代码段。
- 多个函数的日志，可以设置日志前缀表示进行标识，方便查看时过滤。

## 安装

```sh
pip install pysnooper
```

## 例子

- 测试代码1

```python
import pysnooper

@pysnooper.snoop()
def main():
    a = 1
    for i in range(5):
        a += i
main()
```

- 输出1

```
11:11:13.347346 call         5 def main():
11:11:13.347346 line         6     a = 1
New var:....... a = 1
11:11:13.347346 line         7     for i in range(5):
New var:....... i = 0
11:11:13.347346 line         8         a += i
11:11:13.348344 line         7     for i in range(5):
Modified var:.. i = 1
11:11:13.348344 line         8         a += i
Modified var:.. a = 2
11:11:13.348344 line         7     for i in range(5):
Modified var:.. i = 2
11:11:13.348344 line         8         a += i
Modified var:.. a = 4
11:11:13.348344 line         7     for i in range(5):
Modified var:.. i = 3
11:11:13.348344 line         8         a += i
Modified var:.. a = 7
11:11:13.348344 line         7     for i in range(5):
Modified var:.. i = 4
11:11:13.348344 line         8         a += i
Modified var:.. a = 11
11:11:13.348344 line         7     for i in range(5):
11:11:13.348344 return       7     for i in range(5):
Return value:.. None
Elapsed time: 00:00:00.000998
```

- 测试代码2

```python
import pysnooper

@pysnooper.snoop(depth=3)
def main2():
    class Test:
        a = 0
        def __init__(self):
            self.a = 1 + 2

def test(self):
            self.a = 2 + 3

t = Test()
    t.test()
    t.a = 3 + 5
main2()
```

- 输出2

```
11:12:09.174482 call        12 def main2():
11:12:09.174482 line        13     class Test:
    11:12:09.174482 call        13     class Test:
    11:12:09.174482 line        13     class Test:
    New var:....... __module__ = '__main__'
    New var:....... __qualname__ = 'main2.<locals>.Test'
    11:12:09.174482 line        14         a = 0
    New var:....... a = 0
    11:12:09.174482 line        15         def __init__(self):
    New var:....... __init__ = <function main2.<locals>.Test.__init__ at 0x000001FEFD0D5620>
    11:12:09.174482 line        18         def test(self):
    New var:....... test = <function main2.<locals>.Test.test at 0x000001FEFD0D56A8>
    11:12:09.174482 return      18         def test(self):
    Return value:.. None
New var:....... Test = <class '__main__.main2.<locals>.Test'>
11:12:09.174482 line        21     t = Test()
    Starting var:.. self = <__main__.main2.<locals>.Test object at 0x000001FEFD093EB8>
    11:12:09.174482 call        15         def __init__(self):
    11:12:09.174482 line        16             self.a = 1 + 2
    11:12:09.174482 return      16             self.a = 1 + 2
    Return value:.. None
New var:....... t = <__main__.main2.<locals>.Test object at 0x000001FEFD093EB8>
11:12:09.174482 line        22     t.test()
    Starting var:.. self = <__main__.main2.<locals>.Test object at 0x000001FEFD093EB8>
    11:12:09.174482 call        18         def test(self):
    11:12:09.175480 line        19             self.a = 2 + 3
    11:12:09.175480 return      19             self.a = 2 + 3
    Return value:.. None
11:12:09.175480 line        23     t.a = 3 + 5
11:12:09.175480 return      23     t.a = 3 + 5
Return value:.. None
Elapsed time: 00:00:00.001995
```

## 参考

https://github.com/cool-RR/PySnooper
https://www.jianshu.com/p/57d51311aa63
https://blog.csdn.net/zong596568821xp/article/details/99595964

标签: 代码调试

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