Here’s a quick question for you: if you and two values in Python, what is the type of the return? A boolean, right? Nope. Not necessarily.

Here’s an example:

>>> "a" and "b"
'b'

What’s going on here? The reason for this behavior is clearer (at least for me) when you consider how the or operator is commonly used in Python as a way to conditionally assign values in Python in a single line:

name = user_value or "Ahmed" # If user_value is falsy, name becomes "Ahmed"

So when or is used in Python, the operands are evaluated one by one and the first non-falsy operand is returned. If all arguments are falsy, the last one is returned.

Conversely, when and is used, again the operands are evaluated one by one and first falsy one is returned. If all arguments are non-falsy, the last one is returned.

This is provides a nice symmetry and allows both or and and to be used for concise conditional assignment.

In practice, I see and used much less frequently for this purpose. However there are some handy use cases – for example, can you tell what’s happening in this code snippet?

config_port = get_port()  # Returns int, str, or None

port = config_port and int(config_port) or 8000

So to summarize:

• or returns the first non-falsy operand, or the last value
• and returns the first falsy operand, or the last value

Note: When Python needs a boolean value (e.g. in an if statement), it converts arguments into a boolean –> all falsy values are treated as False and truthy values as True, which is why the and and or keywords can be overloaded in the manner above.