How to Print an Exception in Python

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To print an exception in Python, you can either just call print(e) directly on the exception object, or use traceback.print_exc() to print the entire stack trace. You’ll have to import the traceback module to use the second option, though.

How to print just the exception message

Printing exceptions is easy in Python. Since they all (should) implement the __repr__ “dunder” method, calling print() on them will just print a user-friendly message, usually whatever the throwing code put as the error when they raised it.

Here’s an example:

try:
    print("Hello world")
    raise Exception("This is a problem!")
except Exception as e:
    print(e)
Python

We print out “Hello world” and then immediately raise an exception with “This is a problem!” as the message.

Here’s the output:

Hello world
This is a problem!

As you can see, all this prints out is the message we gave to Exception when we instantiated it.

But, this isn’t so great for debugging since we don’t have a stack trace. So, how do we get that?

How to print the stack trace along with the exception

If you want to see the stack trace, you’ll have to import the traceback module and use the print_exc() function within it like this:

import traceback

try:
    print("Hello world")
    raise Exception("This is a problem!")
except Exception as e:
    traceback.print_exc()
Python

You might have noticed we don’t pass in the e instance of the Exception after we catch it; that’s because the traceback.print_exc() function automagically knows what exception we’re dealing with.

Here’s the output:

 Hello world
Traceback (most recent call last):
  File "/home/user/main.py", line 5, in <module>
    raise Exception("This is a problem!")
Exception: This is a problem!

And that’s all there is to printing a stack trace yourself rather than letting an exception go unhandled.

Conclusion

In Python, printing an exception is as easy as catching it (make sure you’re catching the right type!) and then calling print on it. However, you might also want the stack trace. To do that, you simply import the traceback module and call traceback.print_exc() from within an except block.