Python Class: Object-oriented advanced programming __getitem__

Website Explanation:

• object.__getitem__(Self, key)

• Called to implement evaluation ofself[key].for sequence types,The accepted keys should beintegers andSlice Objects. Note that the special interpretation of negative indexes (if the class wishes to emulate a sequence type) are up to the__getitem__()Method. IfKeyis of a inappropriate type,TypeErrorMay is raised; If of a value outside the set of indexes for the sequence (after any special interpretation of negative values),IndexErrorshould be raised. For mapping types, ifKeyIs missing (not in the container),KeyErrorshould be raised.

  Note:

  forLoops expect that anIndexErrorWould be raised for illegal indexes to allow proper detection of the end of the sequence.

For the Fibonacci sequence, when we want to extract the value of a particular position to see, then what to do, and then come out __getitem__ such a function.

int, List type: Slice (no step)

#!/usr/bin/python

#-*-Coding:utf-8-*-

Class Fib (object):

def __getitem__ (self, N):

If Isinstance (n, int): # N is an index

A, B = 1, 1

For x in range (n):

A, B = B, A + b

Return a

If Isinstance (n, Slice): # N is a slice

Start = N.start

Stop = N.stop

If Start is None:

Start = 0

A, B = 1, 1

L = []

For x in range (stop):

If x >= start:

L.append (a)

A, B = B, A + b

Return L

f = Fib ()

Print F[0:4]

Print F[9]

Python Class: Object-oriented advanced programming __getitem__