1. 项目介绍

通过装饰器的方式，对需要调试的函数进行runtime维测输出，包括变量变化，分析路径等，从而避免了通过单步调试的debug方式。

2. 例子

通过 pysnooper.snoop()装饰器装饰待debug的函数接口

  1. import pysnooper
  3. @pysnooper.snoop()
  4. def number_to_bits(number):
  5.     if number:
  6.         bits = []
  7.         while number:
  8.             number, remainder = divmod(number, 2)
  9.             bits.insert(0, remainder)
  10.         return bits
  11.     else:
  12.         return [0]
  14. number_to_bits(6)

The output to stderr is:

  1. Starting var:.. number = 6
  2. 15:29:11.327032 call         4 def number_to_bits(number):
  3. 15:29:11.327032 line         5     if number:
  4. 15:29:11.327032 line         6         bits = []
  5. New var:....... bits = []
  6. 15:29:11.327032 line         7         while number:
  7. 15:29:11.327032 line         8             number, remainder = divmod(number, 2)
  8. New var:....... remainder = 0
  9. Modified var:.. number = 3
  10. 15:29:11.327032 line         9             bits.insert(0, remainder)
  11. Modified var:.. bits = [0]
  12. 15:29:11.327032 line         7         while number:
  13. 15:29:11.327032 line         8             number, remainder = divmod(number, 2)
  14. Modified var:.. number = 1
  15. Modified var:.. remainder = 1
  16. 15:29:11.327032 line         9             bits.insert(0, remainder)
  17. Modified var:.. bits = [1, 0]
  18. 15:29:11.327032 line         7         while number:
  19. 15:29:11.327032 line         8             number, remainder = divmod(number, 2)
  20. Modified var:.. number = 0
  21. 15:29:11.327032 line         9             bits.insert(0, remainder)
  22. Modified var:.. bits = [1, 1, 0]
  23. 15:29:11.327032 line         7         while number:
  24. 15:29:11.327032 line        10         return bits
  25. 15:29:11.327032 return      10         return bits
  26. Return value:.. [1, 1, 0]

3. 额外功能

PySnooper 通过装饰器传入参数的方式进行debug参数传入。可选参数有：

  1. output重定向
  1. @pysnooper.snoop('/my/log/file.log')
  1. 查看non-local变量
  1. @pysnooper.snoop(variables=('foo.bar', 'self.whatever'))
  1. 设置debug调用深度
  1. @pysnooper.snoop(depth=2)
  1. 设置所有的输出prefix字符串
  1. @pysnooper.snoop(prefix='ZZZ ')