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Python '!=' Is Not 'is not': Comparing Objects in Python (Overview)

There’s a subtle difference between the Python identity operator (is) and the equality operator (==). Your code can run fine when you use the Python is operator to compare numbers, until it suddenly doesn’t. You might have heard somewhere that the Python is operator is faster than the == operator, or you may feel that it looks more Pythonic. However, it’s crucial to keep in mind that these operators don’t behave quite the same.

The == operator compares the value or equality of two objects, whereas the Python is operator checks whether two variables point to the same object in memory. In the vast majority of cases, this means you should use the equality operators == and !=, except when you’re comparing to None.

In this course, you’ll learn:

  • What the difference is between object equality and identity
  • When to use equality and identity operators to compare objects
  • What these Python operators do under the hood
  • Why using is and is not to compare values leads to unexpected behavior
  • How to write a custom __eq__() class method to define equality operator behavior

Sample Code (.zip)

2.5 KB

Course Slides (.pdf)

260.6 KB

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