How to assign a NULL value to a pointer in python

Question

I am C programmer  I am new to python  In C   when we define the structure of a binary tree node we assign NULL to it s right and left child as      struct node        int val        struct node  right         struct node  left             And when initializing a node   we write as      val   some value   right   NULL    left   NULL      Now my question is  how can we assign a NULL value to right and left pointers of the node in Python    And how can we test against the Python version of NULL   In C it would be   if  ptr- gt right    NULL     Thank you

User · Answer

left   None  left is None  evaluates to True

User · Answer

All objects in python are implemented via references so the distinction between objects and pointers to objects does not exist in source code   The python equivalent of NULL is called None  good info here   As all objects in python are implemented via references  you can re-write your struct to look like this   class Node      def   init   self    object initializer to set attributes  fields          self val   0         self right   None         self left   None   And then it works pretty much like you would expect   node   Node   node val   some val  always use   as everything is a reference and - gt  is not used node left   Node     Note that unlike in NULL in C  None is not a  pointer to nowhere   it is actually the only instance of class NoneType  Therefore  as None is a regular object  you can test for it just like any other object   if node left    None     print  The left node is None Null      Although since None is a singleton instance  it is considered more idiomatic to use is and compare for reference equality   if node left is None     print  The left node is None Null

User · Answer

Normally you can use None  but you can also use objc NULL  e g   import objc val   objc NULL   Especially useful when working with C code in Python   Also see  Python objc NULL Examples

[python] How to assign a NULL value to a pointer in python?

Examples related to python