python - 在堆栈跟踪中打印函数的参数值

Question

当打印错误堆栈跟踪时，我们如何在调用堆栈中打印传递给函数的参数值？我希望输出与下面的示例完全相同。

例子:

Traceback (most recent call last):
  File "./file.py", line 615, in func0 **(arg0) arg0 = 0 was passed**
    result = func1(arg1, arg2)
  File "./file.py", line 728, in func1 **(arg1, arg2) arg1 = 1 and arg2 = 2 was passed**
    return int_value[25]
TypeError: 'int' object is not iterable

除了堆栈跟踪中的正常输出之外，我还希望上面 ** ** 中的信息也被打印出来。我设想的是调试器也会自动打印传递的参数。这将清楚地显示数据通过的“功能管道”，管道中发生了什么，以及哪个功能没有做它应该做的事情。这将有助于调试很多。

我搜索了很多，发现了这些相关问题:

• How to print call stack with argument values?
• How to print function arguments in sys.settrace?

但它们的答案都不适合我:第一个答案导致 ModuleNotFoundError: No module named 'stackdump'。第二个问题的答案使我的 ipython 解释器崩溃，堆栈跟踪非常长。

我也查了一下:

• https://docs.python.org/3/library/sys.html#sys.settrace
• https://docs.python.org/3/library/traceback.html

TracebackException 似乎有一个capture_locals 变量，但我不太明白如何让它工作。

Answer 1

纯Python3

谈到 TracebackExceptions 和它的 capture_locals 参数，我们可以按如下方式使用它:

#!/usr/bin/env python3

import traceback

c = ['Help me!']

def bar(a = 3):
    d = {1,2,3}
    e = {}
    foo(a)

def foo(a=4):
    b = 4
    if a != b:
        raise Exception("a is not equal to 4")

try:
    bar(3)
except Exception as ex:
    tb = traceback.TracebackException.from_exception(ex, capture_locals=True)
    print("".join(tb.format()))

打印每一帧的所有局部变量:

$ ./test.py 
Traceback (most recent call last):
  File "./test.py", line 21, in <module>
    bar(3)
    __annotations__ = {}
    __builtins__ = <module 'builtins' (built-in)>
    __cached__ = None
    __doc__ = None
    __file__ = './test.py'
    __loader__ = <_frozen_importlib_external.SourceFileLoader object at 0x7f81073704c0>
    __name__ = '__main__'
    __package__ = None
    __spec__ = None
    bar = <function bar at 0x7f81073b11f0>
    c = ['Help me!']
    ex = Exception('a is not equal to 4')
    foo = <function foo at 0x7f810728a160>
    traceback = <module 'traceback' from '/usr/lib/python3.8/traceback.py'>
  File "./test.py", line 11, in bar
    foo(a)
    a = 3
    d = {1, 2, 3}
    e = {}
  File "./test.py", line 17, in foo
    raise Exception("a is not equal to 4")
    a = 3
    b = 4
Exception: a is not equal to 4

看起来有点过于冗长，但有时这些数据对于调试某些崩溃可能至关重要。

洛古鲁

还有一个包loguru打印“Fully descriptive exceptions”:

2018-07-17 01:38:43.975 | ERROR    | __main__:nested:10 - What?!
Traceback (most recent call last):

  File "test.py", line 12, in <module>
    nested(0)
    └ <function nested at 0x7f5c755322f0>

> File "test.py", line 8, in nested
    func(5, c)
    │       └ 0
    └ <function func at 0x7f5c79fc2e18>

  File "test.py", line 4, in func
    return a / b
           │   └ 0
           └ 5

ZeroDivisionError: division by zero