Python iterators and generators

Iterators

Essentially, an iterator is an object that has a next () method

Iterators can be created using the built-in iter method

>>> i = iter ('abc')>>> i.next ()'a '>>> i.next ()'b'>>> i.next () ' C '

To create iterators for classes available __iter__ and next ()

classFib (object):def __init__(self): SELF.A, self.b= 0, 1#Initialize two counters A, B    def __iter__(self):returnSelf#The instance itself is an iterative object, so it returns itself    defNext (self): SELF.A, self.b= self.b, SELF.A + self.b#Calculate Next Value        ifSELF.A > 100000:#conditions for exiting a loop            Raisestopiteration (); returnSelf.a#returns the next value forNinchFib ():PrintN-------------------------------11235...4636875025

Generator

The generator can be iterated, but it can only be read once

 for  in range (3)) -in GT: ...     Print (i) 0  for inch g:     ... Print (i)

yield

 #   When you call this function, the code inside the function does not execute immediately,    This function simply returns a generator object  def   CreateGenerator (): MyList  = range (3 for  i in   MyList:  yield  i*i  >>> for  i in   Mygenerator:  print   I0  14> >> for  i in  mygenerator: #   is also callable only once  print  i 

2015-05-26

Python iterators and generators