TP wrote: > Hi everybody, > > Be a the following list, containing list elements which second field is a > string. > >>>> a = [ [4, "toto"], [5, "cou"] ] >>>> a[0][1]="tou" >>>> a > [[4, 'tou'], [5, 'cou']] > > OK. > > Now, I want: > * to do the same modification on the list "a" within a function > * not to hardcode in this function the position of the string in each > element of a. > > At first sight, we think at defining a function like this: > > def assign( text_accessor, list_elem, new_textvalue ): > > text_accessor( list_elem ) = new_textvalue > > and then doing: > > assign( lambda elem: elem[1], a[0], "co" ) > > But it does not work, we obtain: > > text_accessor( list_elem ) = new_textvalue > SyntaxError: can't assign to function call > > In fact, we should work on the address of text_accessor( list_elem ). How > to do that?
You can understand Python to some extend if you liken its variables to pointers, but here the analogy breaks: you cannot have pointers to pointers. To parameterize list item access you can either pass the index or a setter (and if needed a getter) function: >>> a = [ [4, "toto"], [5, "cou"] ] >>> def assign(setitem_n, items, value): ... setitem_n(items, value) ... >>> def setitem1(items, value): ... items[1] = value ... >>> assign(setitem1, a[0], "XX") >>> a [[4, 'XX'], [5, 'cou']] Peter -- http://mail.python.org/mailman/listinfo/python-list
