The **`assert` statement** is a sanity check statement, used when debugging code. 

It is an *alternative* to an if statement. It gives an AssertionError exception if the expression inside the assert evaluates to be false and no error. It is basically an internal self-check within the code. 

# Syntax
Assertion statement takes an expression and an optional error message as an input.

The general syntax is:
```python
assert(expression)
``` 
A custom error message can also be displayed if the assertion condition evaluates to be false.

```python
assert expression, message
```

The following flow chart explains the concept:



# What can assertion do?
* It can check the type and value of the argument as well as the output of the function.
* It can be used as a debugging tool since it halts the program where the statements execute to be false.


# Examples

## 1. Without a custom error message
The following code explains how to use the `assert` in python:

x="Python Programming"
assert(x=="Python Programming") # no error
assert(x=="Python Language") # Assertion error 

## 2. With a custom error message
The following example uses assert with a custom error message defined:
>**Note:** When writing a custom message, do not put a bracket around the assert condition

assert False, "We've got a problem" #custom error message
assert 2 + 2 == 5, "We've got a problem" #custom error message

What does assert mean in Python?

The assert statement in Python is a debugging tool that halts a program if a specified condition is false, optionally displaying a custom error message.