Complex sentence: In that case, the parameter need not necessarily be named this or self; it can be named freely by the programmer like any other parameter; however, by informal convention, the first parameter of an instance method in Perl and Python is named self.
Split into simpler sentences: In that case, the parameter need not necessarily be named this or self; it can be named freely by the programmer like any other parameter. However, by informal convention, the first parameter of an instance method in Perl or Python is named self.