where()¶

Python traceback give information about where an exception was raised and more. But it does so in a way that’s not entirely friendly to users. Let’s look at a different example, and see how friendly can give a bit more information about the location of the problem.

>>> test_4(42)

Traceback (most recent call last):
  File "<friendly-console:10>", line 1, in <module>
    test_4(42)

       ... More lines not shown. ...

    test_2(x)
  File "<friendly-console:7>", line 2, in test_2
    test_1(x)
  File "<friendly-console:8>", line 3, in test_1
    print(arg + something + others)
NameError: name 'others' is not defined

Did you mean other?

By default, friendly limits the length of the traceback shown to the user. [If you want to see a full traceback instead, use python_tb() or see Multiple tracebacks for more details.] Still, Python tracebacks can be rather too terse looking for beginners, making it difficult for them to grasp where the error occurred.

Let’s see how where() can get a bit more information about this:

>>> where()

Execution stopped on line 1 of file '<friendly-console:10>'.

    -->1: test_4(42)

    test_4: <function test_4>

Exception raised on line 3 of file '<friendly-console:8>'.

       1: def test_1(arg):
       2:     other = 3
    -->3:     print(arg + something + others)
                                      ^^^^^^

    arg: 42
    global something: 4
    print: <builtin function print>
>>>

friendly gives detailed information about two locations at most: where the program stopped and where the exception was raised. It shows a few lines of code near the source of the problem, and gives some information about what it thinks might be relevant identifiers.