Convert exception error to string

Question

I want to work with the error message from an exception but can't seem to convert it to a string. I've read the os library man page but something is not clicking for me.

Printing the error works:

try:
    os.open("test.txt", os.O_RDONLY)
except OSError as err:
    print ("I got this error: ", err)

But this does not:

try:
    os.open("test.txt", os.O_RDONLY)
except OSError as err:
    print ("I got this error: " + err)

TypeError: Can't convert 'FileNotFoundError' object to str implicitly

score 78 · Answer 1 · answered Dec 10 '17 at 00:16

78

In my experience what you want is repr(err), which will return both the exception type and the message.

str(err) only gives the message.

answered Dec 10 '17 at 00:16

Hendy Irawan

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This is a much more useful answer, although it'll only work if you are doing debugging/don't already know what you're catching for. – Spcogg the second May 12 '20 at 08:12

miradulo · Accepted Answer · 2016-06-07T16:17:54.727

47

From the docs for print()

All non-keyword arguments are converted to strings like str() does and written to the stream

So in the first case, your error is converted to a string by the print built-in, whereas no such conversion takes place when you just try and concatenate your error to a string. So, to replicate the behavior of passing the message and the error as separate arguments, you must convert your error to a string with str().

edited Jun 07 '16 at 16:17

answered Jun 07 '16 at 16:04

miradulo

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Therefore wrapping err in str() as in str(err) works. Thanks. – dpetican Jun 07 '16 at 16:06
3

The problem is that it only "prints" the error message but not the error type. How do we print both the type and message in short code, just like Python does it? – Hendy Irawan Dec 09 '17 at 05:50
1

@HendyIrawan Multiple approaches, see https://stackoverflow.com/a/9824050/4686625 – miradulo Dec 09 '17 at 13:34

Convert exception error to string

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