Hello Giovanni, you have hit one of my favorite Python Pitfalls: Python does always call by value, but sometimes it behaves like call by reference .
The explanation is hidden in a footnote in the tutorial. Please see "Defining Functions" in "More Control Flow Tools" in the Python Tutorial: http://docs.python.org/tutorial/controlflow.html#defining-functions "The actual parameters (arguments) to a function call are introduced in the local symbol table of the called function when it is called; thus, arguments are passed using call by value (where the value is always an object reference, not the value of the object). [1] When a function calls another function, a new local symbol table is created for that call." And the footnotes is: [1] Actually, call by object reference would be a better description, since if a mutable object is passed, the caller will see any changes the callee makes to it (items inserted into a list). With best regards, Lars --~--~---------~--~----~------------~-------~--~----~ To post to this group, send email to sage-support@googlegroups.com To unsubscribe from this group, send email to sage-support-unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/sage-support URLs: http://www.sagemath.org -~----------~----~----~----~------~----~------~--~---
