So to set this new variable to ‘None’ in python, it needs to a be “int or None” and to write that in python (which is very new for python) we would need “a: Union”. How can an ‘int’ have type noted, but not actually yet exist? The reality is in python we could set our variable to ‘None’ to indicate it has no value, and then the variable would actually exist, but then ‘None’ is not an int ‘type(None)’. It says “the variable called ‘a’ will be an int, but does not yet exist”.

What this code does is, at best, a little strange.

what is null? ( see Nulllable, null, None…)Ĭonsider the python code in Python Variables, where the first line reads “a: int”.

Python has no ‘null’ (see Nullable, null, None, …) and the Python ‘None’ is more accurately an equivalent to the kotlin ‘Unit’. The problem will arise in a different way (most often ‘NoneType object has no attribute…’, or a TypeError as above) but the lack of a true equivalent to Null excludes Python code from a very elegant solution to handling special cases, and forces more exception handling. Truth is, the ‘null’ (or None) problem is still there for python programs. Whoopsy! Null safety is the language ensuring you never make the mistake of forgetting to check for ‘null’ when you need to check. But what if there is a case when the program accidentally does not set ‘foo’? If you try and add the python equivalent of ‘null’ (None) to an int value, the error “TypeError: unsupported operand type(s) for +: ‘int’ and ‘NoneType'” will be raised. A variable ‘foo’ which is to be an ‘int’ could be set to ‘null’ until an actual value is calculated and set. Null is normally a placeholder for a value, only used where the value is not yet known. Null safety is all about preventing code from accidentally using a value which is null. So what is ‘null’ safety? Firstly, if you any questions on what ‘null’ is, then check the page None, Unit, Nothing, void and null.

To python programmers, ‘Null Safety’ can sound like solving a problem they never had. To java programmers, ‘Null Safety’ can sound like the ‘Holy Grail’.

If null kotlin