python - 异常堆栈跟踪中的 locals() 和 globals() (Python)

Question

虽然堆栈跟踪在 Python 中很有用，但大多数情况下问题根源的数据都丢失了 - 有没有办法确保至少将 locals()（可能还有 globals()）添加到打印的堆栈跟踪中？

Answer 1

您可以安装自己的异常挂钩并从那里输出您需要的内容：

import sys, traceback

def excepthook(type, value, tb):
    traceback.print_exception(type, value, tb)

    while tb.tb_next:
        tb = tb.tb_next

    print >>sys.stderr, 'Locals:',  tb.tb_frame.f_locals
    print >>sys.stderr, 'Globals:', tb.tb_frame.f_globals

sys.excepthook = excepthook

def x():
    y()

def y():
    foo = 1
    bar = 0

    foo/bar

x()

要打印回溯中每一帧的变量，请将上述循环更改为

    while tb:
        print >>sys.stderr, 'Locals:',  tb.tb_frame.f_locals
        print >>sys.stderr, 'Globals:', tb.tb_frame.f_globals
        tb = tb.tb_next

Answer 2

这是一个潘多拉魔盒。打印形式的值可能非常大；在堆栈跟踪中打印所有本地变量很容易由于错误输出而导致新问题。这就是为什么这在 Python 中一般没有实现。

但是，在一些小例子中，即如果您知道您的值不会太大而无法正确打印，您可以自己进行回溯：

import sys
import traceback

def c():
  clocal = 1001
  raise Exception("foo")

def b():
  blocal = 23
  c()

def a():
  alocal = 42
  b()

try:
  a()
except Exception:
  frame = sys.exc_info()[2]
  formattedTb = traceback.format_tb(frame)    
  frame = frame.tb_next
  while frame:
    print formattedTb.pop(0), '\t', frame.tb_frame.f_locals
    frame = frame.tb_next

输出将是这样的：

  File "/home/alfe/tmp/stacktracelocals.py", line 19, in <module>
    a()
        {'alocal': 42}
  File "/home/alfe/tmp/stacktracelocals.py", line 16, in a
    b()
        {'blocal': 23}
  File "/home/alfe/tmp/stacktracelocals.py", line 12, in b
    c()
        {'clocal': 1001}

当然，您可以按照他的回答中建议的 thg435 安装自己的除钩子。

Answer 3

如果您还不知道这一点，请使用 pdb 事后分析功能：

x = 3.0
y = 0.0
print x/y
def div(a, b):
    return a / b
print div(x,y)
---------------------------------------------------------------------------
ZeroDivisionError                         Traceback (most recent call last)
<ipython-input-3-d03977de5fc3> in div(a, b)
      1 def div(a, b):
----> 2     return a / b

ZeroDivisionError: float division

import pdb
pdb.pm()
> <ipython-input-3-148da0dcdc9e>(2)div()
      0     return a/b

ipdb> l
      1 def div(a,b):
----> 2     return a/b

ipdb> a
3.0
ipdb> b
0.0

等等

当然，在某些情况下您确实需要打印。你最好检测代码（通过try / except）以打印出你正在调试的特定奇怪异常的额外信息，而不是把它放在所有东西上，恕我直言。

Answer 4

尝试traceback-with-variables包。

用法：

from traceback_with_variables import traceback_with_variables

def main():
    ...
    with traceback_with_variables():
        ...your code...

例外情况：

Traceback with variables (most recent call last):
  File "./temp.py", line 7, in main
    return get_avg_ratio([h1, w1], [h2, w2])
      sizes_str = '300 200 300 0'
      h1 = 300
      w1 = 200
      h2 = 300
      w2 = 0
  File "./temp.py", line 10, in get_avg_ratio
    return mean([get_ratio(h, w) for h, w in [size1, size2]])
      size1 = [300, 200]
      size2 = [300, 0]
  File "./temp.py", line 10, in <listcomp>
    return mean([get_ratio(h, w) for h, w in [size1, size2]])
      .0 = <tuple_iterator object at 0x7ff61e35b820>
      h = 300
      w = 0
  File "./temp.py", line 13, in get_ratio
    return height / width
      height = 300
      width = 0
builtins.ZeroDivisionError: division by zero

安装：

pip install traceback-with-variables