Intermediate classes

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Required course material for the lesson

Powerpoint: Classes
Resource: Example code - Classes

Subjects covered

Magic methods in classes
Object Oriented Programming
Polymorphism and inheritance
Practical knowledge

Exercises to be handed in

The first two exercises will continue with the Fasta class from last time.

1. Use magic methods to add iteration and length evaluation (using __iter__ and __len__ magic methods) to the Fasta class. Do this so you can write code like
   if len(MyFastaInstance) > 0:
       for header, sequence in MyFastaInstance:
           # Do something with header and sequence
           print(header, sequence)
   The function len returns the number of sequences.
   
   
2. Add the methods deletethis(), insertthis(header, sequence), verifythis(alphabet) and discardthis(alphabet) to the Fasta class. The methods should only work when iterating over an instance at the current item, i.e. they work when you are iterating over the fasta sequences on the current sequence and header, like this:
   for header, sequence in MyFastaInstance:
       if not MyFastaInstance.verifythis("DNA"):
           MyFastaInstance.deletethis()
           continue
       # Do something with header and sequence
   As some may remember, it is normally impossible to successfully iterate straightforward through a list and delete and/or add elements to the list during the iteration. You have to make this possible, maybe by changing the way your iteration works in the previous exercise.