[snip] >I'm used to c > variables going out of scope once you leave the called function. I > imagine if you want to leave the variables unchanged, you have to > re-assign them inside the function. [snip]
Lists are mutable objects. When you pass a list to a function you bind a name in the functions namespace to the list object. Every name binding to that object will have the ability to modify the list. If you want to modify the list but not change it for others usually you do something like new_list = list( old_list ) OR new_list = old_list[:] Now if you wanted to change an immutable object (like int) then you would have to return object because the name binding is only the function's scope. It should also be noted that you can modify the list but you cannot reassign the list from the function. Consider: >>> >>> def blah( a ): ... a = [] ... >>> b = [ 1, 3, 4 ] >>> blah( b ) >>> print b [1, 3, 4] >>> The reason b is untouched is because a = [] just binds the name 'a' to a new list object while the name 'b' is still bound to the original list object. To bind 'b' to the new list I would have had to return it from blah(). Ramit Ramit Prasad | JPMorgan Chase Investment Bank | Currencies Technology 712 Main Street | Houston, TX 77002 work phone: 713 - 216 - 5423 -- This email is confidential and subject to important disclaimers and conditions including on offers for the purchase or sale of securities, accuracy and completeness of information, viruses, confidentiality, legal privilege, and legal entity disclaimers, available at http://www.jpmorgan.com/pages/disclosures/email. _______________________________________________ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
