python:如何在我的代码发出最后一个错误之前起床

Question

所以,当我运行这个...错误是在这一行,bomb=pd.DataFrame(here,0)但跟踪显示了一堆来自pandas库的代码来获取错误.

import traceback,sys
import pandas as pd        

def error_handle(err_var,instance_name=None): #err_var list of variables, instance_name
    print(traceback.format_exc())
    a= sys._getframe(1).f_locals

    for i in err_var: # selected var for instance
        t= a[instance_name]
        print i,"--->",getattr(t,i.split(".")[1])



here=['foo']

err_var = ['self.needthisone','self.constant2']
class test:

    def __init__(self):
        self.constant1 = 'hi1'
        #self.constant2 = 'hi2'
        #self.needthisone = ':)'
        for i in err_var:
            setattr(self, i.split('.')[1], None)

    def other_function(self):
        self.other_var=5

    def testing(self):
        self.other_function()
        vars=[self.constant1,self.constant2]

        try:
            for i in vars: 
                bomb=pd.DataFrame(here,0)

        except:
            error_handle(err_var,'self')

t=test()
t.testing()    

如何抑制所有这些并使错误看起来像这样:

Traceback (most recent call last):
  File "C:\Users\Jason\Google Drive\python\error_handling.py", line 34, in testing
    bomb=pd.DataFrame(here,0)
TypeError: Index(...) must be called with a collection of some kind, 0 was passed

我只想知道与我相关的内容以及我编写的最后一行代码,这些代码很糟糕.

这是原作:

Traceback (most recent call last):
  File "C:\Users\Jason\Google Drive\python\error_handling.py", line 35, in testing
    bomb=pd.DataFrame(here,0)
  File "C:\Python27\lib\site-packages\pandas\core\frame.py", line 330, in __init__
    copy=copy)
  File "C:\Python27\lib\site-packages\pandas\core\frame.py", line 474, in _init_ndarray
    index, columns = _get_axes(*values.shape)
  File "C:\Python27\lib\site-packages\pandas\core\frame.py", line 436, in _get_axes
    index = _ensure_index(index)
  File "C:\Python27\lib\site-packages\pandas\core\indexes\base.py", line 3978, in _ensure_index
    return Index(index_like)
  File "C:\Python27\lib\site-packages\pandas\core\indexes\base.py", line 326, in __new__
    cls._scalar_data_error(data)
  File "C:\Python27\lib\site-packages\pandas\core\indexes\base.py", line 678, in _scalar_data_error
    repr(data)))
TypeError: Index(...) must be called with a collection of some kind, 0 was passed

self.needthisone ---> None
self.constant2 ---> None

Answer 1

我强烈建议您不要限制回溯输出，因为这是不好的做法。你感觉信息太多；但这只是因为您已经看过它并且知道要查找什么错误。

在大多数情况下，问题可能隐藏在其他地方。因此，必须有一种更好的方法来实现您所寻求的目标。

为什么不将函数调用包装在try except子句中并打印异常消息？以这个场景为例：

def f():
    a = 0
    i = 1
    print i/a

def another_func():
    print 'this is another func'
    return f()

def higher_level_func():
    print 'this is higher level'
    return another_func()


if __name__ == '__main__':
    try:
        higher_level_func()
    except Exception as e:
        print 'caught the exception: {}-{}'.format(type(e)__name__, e.message)

调用时，输出如下：

this is higher level
this is another func
caught the exception: ZeroDivisionError-integer division or modulo by zero

这仅打印代码中的相关异常，隐藏有关回溯的任何信息，但回溯仍然可用，您也可以打印它（只需从 except 块中引发异常）。

与此相比，如果我删除该try except块：

this is higher level
this is another func
caught the exception: integer division or modulo by zero
Traceback (most recent call last):
  File "test.py", line 17, in <module>
    higher_level_func()
  File "test.py", line 12, in higher_level_func
    return another_func()
  File "test.py", line 8, in another_func
    return f()
  File "test.py", line 4, in f
    print i/a
ZeroDivisionError: integer division or modulo by zero

您最好使用此技术来捕获相关异常，而不是限制回溯。如果您希望程序停止，只需添加sys.exit(1)该except块即可。