CODEWITHSUNDEEP
pythonlogicassert
Mark Puchala II
Mark Puchala II

Reputation: 652

Assert without the traceback in Python

I'm trying to simplify the following:

if x < 0:
  print('we don't do negative numbers')
else: 
  NORMAL CODE HERE

I recently learned of the assert command, and admire its ability to simplify my previous lines into:

assert x > 0, 'errorText'
NORMAL CODE HERE

I don't want errors to give a traceback, though. I only want that single line like the if/else gives.

Is there a way to get an assertionError to return single line like exceptions do, or do I really need to keep running if/else's everywhere?

Upvotes: 4

Views: 4316

Answers (1)

Noah
Noah

Reputation: 1731

The assert statement in Python is intended for debugging or for testing. It serves the purpose of halting execution of the program when the condition is not True. When debugging you can include these statements in your code to help track down errors. Then remove them once the bug is fixed. Using assert in production code is a bad idea.

As you have it written using assert, your program will terminate if x is less than zero and the code that follows will not run.

You should continue to use if/else method to provide the two desired code paths. One path to log that x is less than zero, the other path to execute the code in the block NORMAL CODE HERE.

If x should never be less than 0 at this point, and the remaining code must not be executed then you should raise an Exception that can be caught in the calling code.

def method_using_positive_numbers(x):
    if x < 0:
        raise ValueError("we don't do negative numbers")
    NORMAL CODE HERE

Another option is to return from the method if the condition is not true.

def method_using_positive_numbers(x):
    if x < 0:
        print("we don't do negative numbers")
        return
    NORMAL CODE HERE

Upvotes: 8

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