Luciano Ramalho

Luciano Ramalho was a Web developer before the Netscape IPO in 1995, and switched from Perl to Java to Python in 1998. Since then he worked on some of the largest news portals in Brazil using Python, and taught Python web development in the Brazilian media, banking and government sectors. His speaking credentials include PyCon US (2013), OSCON (2002, 2013), and 15 talks over the years at PythonBrasil (the Brazilian PyCon) and FISL (the largest FLOSS conference in the Southern Hemisphere). Ramalho is a member of the Python Software Foundation and co-founder of Garoa Hacker Clube, the first hackerspace in Brazil. He is co-owner of, a training company.

Python tuples: immutable but potentially changing

Think labels, not boxes

Python tuples have a surprising trait: they are immutable, but their values may change. This may happen when a tuple holds a reference to any mutable object, such as a list. If you need to explain this to a colleague who is new to Python, a good first step is to debunk the common notion that variables are like boxes where you store data.

In 1997 I took a summer course about Java at MIT. The professor, Lynn Andrea Stein — an award-winning computer science educator — made the point that the usual “variables as boxes” metaphor actually hinders the understanding of reference variables in OO languages. Python variables are like reference variables in Java, so it’s better to think of them as labels attached to objects.

Here is an example inspired by Lewis Carroll’s Through the Looking-Glass, and What Alice Found There.


Tweedledum and Tweedledee are twins. From the book: “Alice knew which was which in a moment, because one of them had ‘DUM’ embroidered on his collar, and the other ‘DEE’.”

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