CODEWITHSUNDEEP
pythonerror-handlingassert
Jirka
Jirka

Reputation: 421

raise Assertionerror vs. assert python

What are the big differences between raise AssertionError and assert to build in a "fault"? What are the effects on the code? And is one or the other more pythonic in a way?

The reason for my question is because I am learning to program. Right now we have an exercise where for example when x != 0 we need to get an AssertionError "false".

I looked this up online, where I found the following code:

if x != 0:
    raise AssertionError ("false")

But my teachers also use the following a lot:

assert x == 0,"fout"

What are the (dis)advantages of each approach?

Thanks a lot in advance.

Upvotes: 20

Views: 27884

Answers (1)

John Gordon
John Gordon

Reputation: 33275

Those two code examples are equivalent, with the exception that assert statements can be globally disabled with the -O command-line flag.

See:

# script.py
assert 0, "statement"
raise AssertionError("error")

Which produces different errors with and without the -O flag:

$ python  script.py 
Traceback (most recent call last):
  File "/tmp/script.py", line 1, in <module>
    assert 0, "statement"
AssertionError: statement
$ python -O script.py 
Traceback (most recent call last):
  File "/tmp/script.py", line 2, in <module>
    raise AssertionError("error")
AssertionError: error

Upvotes: 24

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