Explain about assert statement?
Assertion :
- An assertion is a sanity-check that you can turn on or turn off when you are done with your testing of the program.
- We often place assertions at the start of a function to check for valid input, and after a function call to check for valid output.
The assert Statement :
- When encounters an assert statement, Python evaluates the accompanying expression, which is hopefully true. If the expression is false, Python raises an AssertionError exception.
- Syntax :
- assert Expression[, Arguments]
- If the assertion fails, Python uses ArgumentExpression as the argument for the AssertionError.
- AssertionError exceptions can be caught and handled like any other exception using the try-except statement, but if not handled, they will terminate the program and produce a traceback.
- Ex :
>>> def addOne(n):
... assert (n >= 0),"n should be greator than or equal to 0."
... return n + 1
...
>>> addOne(1)
2
>>> addOne(-1)
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "<stdin>", line 2, in addOne
AssertionError: n should be greator than or equal to 0.
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