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pythonexception
John Stud
John Stud

Reputation: 1779

Python: How to store exception value?

How might I store the value of an exception as a variable? Looking at older posts, such as the one below, these methods do not work in Python3. What should I do without using a pip install package?

My goal is to iterate through data, checking it all for various things, and retain all the errors to put into a spreadsheet.

Older post: Python: catch any exception and put it in a variable

MWE:

import sys

# one way to do this
test_val = 'stringing'
try:
    assert isinstance(test_val, int), '{} is not the right dtype'.format(test_val)
except AssertionError:
    the_type, the_value, the_traceback = sys.exc_info()

Upvotes: 1

Views: 657

Answers (2)

a_guest
a_guest

Reputation: 36249

If you want to test whether a certain variable is of type int, you can use isinstance(obj, int) as you already do.

However you should never use assert to validate any data, since these checks will be turned off when Python is invoked with the -O command line option. assert statements serve to validate your program's logic, i.e. to verify certain states that you can logically deduce your program should be in.

If you want to save whether your data conforms to some criteria, just store the True or False result directly, rather than asserting it and then excepting the error (beyond the reasons above, that's unnecessary extra work).

Upvotes: 2

Peter DeGlopper
Peter DeGlopper

Reputation: 37319

except AssertionError as err:

For more details like unpacking the contents of the exception, see towards the bottom of this block of the tutorial, the paragraph that begins "The except clause may specify a variable after the exception name."

Upvotes: 2

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