Understand assert in C++, C and Python

assert is a macro or function used to check conditions that should be true at runtime. If the condition fails, the program usually exits, and an error message is displayed. It is a useful tool for debugging, ensuring that certain conditions are met during development.

Using `assert` in C++ and C

In C++ and C, assert is a macro defined in the header <cassert> (C++) or <assert.h> (C). It is primarily used to validate assumptions at runtime and can be disabled in production code by defining the NDEBUG macro.

Performance: assert should be used primarily for debugging. In production code, it is common to disable it to improve performance.
Error Messages: Whenever possible, provide a descriptive message to facilitate debugging, especially in large projects.
Exceptions: For critical validations, consider using exceptions (in C++ or Python) or manual checks that are never disabled.

Example in C++

#include <iostream>
#include <cassert>

int divide(int a, int b) {
assert(b != 0 && "Divisor cannot be zero!");
return a / b;
}

int main() {
int x = 10;
int y = 0;

std::cout << "Division: " << divide(x, y) << std::endl;

return 0; }

In this example, assert(b != 0) ensures that the divisor is never zero. If y is zero, execution will stop with an error message.

Example in C

#include <stdio.h>
#include <assert.h>

int divide(int a, int b) {
assert(b != 0 && "Divisor cannot be zero!");
return a / b;
}

int main() {
int x = 10;
int y = 0;

printf("Division: %d\n", divide(x, y));

return 0;
}

The operation is the same as in the C++ example, since assert in C is also used to check the validity of conditions at runtime.

Using `assert` in Python

In Python, assert is a native language statement that works in a similar way. If the condition is false, an AssertionError exception is thrown. As in C/C++, asserts can be disabled in the production environment using the -O flag (optimize, python -O script.py) when running the script.

def divide(a, b):
assert b != 0, "Divisor cannot be zero!"
return a / b

x = 10
y = 0

print("Division:", divide(x, y))

In this example: assert b != 0 checks if b is non-zero. If y is zero, an AssertionError will be raised with the message “Divisor cannot be zero!”, if you do not use assert or if you use the parameter: -O as mentioned, the error output will be different.

There are many implementations of assert mainly in software that does unit testing, it is a powerful tool to avoid failures!

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