Menu
I need to process a pointer to get its value via a callback. This is problematic since this pointer is null during the first call. So doing a pointer.contents does ValueError: NULL pointer access. To avoid this, how to check if the pointer is null ?
443
Use Pointer Value as Condition to Check if Pointer Is NULL in C++ Null pointers are evaluated as false when they are used in logical expressions. Thus, we can put a given pointer in the if statement condition to check if it's null.
Use the is operator to check if a variable is null in Python, e.g. if my_var is None: . The is operator returns True if the values on the left-hand and right-hand sides point to the same object and should be used when checking for singletons like None .
There's no null in Python. Instead, there's None. As stated already, the most accurate way to test that something has been given None as a value is to use the is identity operator, which tests that two variables refer to the same object. In Python, to represent an absence of the value, you can use a None value (types.
Hence when a pointer to a null pointer is created, it points to an actual memory space, which in turn points to null. Hence Pointer to a null pointer is not only valid but important concept.
NULL Pointers have a boolean False value, so:
if pointer:
x = pointer.contents
else:
print "NULL pointer"
Edited for indentation
76
If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With
