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Diffstat (limited to 'Doc/tut/tut.tex')
| -rw-r--r-- | Doc/tut/tut.tex | 27 |
1 files changed, 14 insertions, 13 deletions
diff --git a/Doc/tut/tut.tex b/Doc/tut/tut.tex index a0b75c6..4abd0bd 100644 --- a/Doc/tut/tut.tex +++ b/Doc/tut/tut.tex @@ -4488,34 +4488,35 @@ This style of access is clear, concise, and convenient. The use of iterators pervades and unifies Python. Behind the scenes, the \keyword{for} statement calls \function{iter()} on the container object. The function returns an iterator object that defines the method -\method{next()} which accesses elements in the container one at a -time. When there are no more elements, \method{next()} raises a +\method{__next__()} which accesses elements in the container one at a +time. When there are no more elements, \method{__next__()} raises a \exception{StopIteration} exception which tells the \keyword{for} loop -to terminate. This example shows how it all works: +to terminate. You can call the \method{__next__()} method using the +\function{next()} builtin; this example shows how it all works: \begin{verbatim} >>> s = 'abc' >>> it = iter(s) >>> it <iterator object at 0x00A1DB50> ->>> it.next() +>>> next(it) 'a' ->>> it.next() +>>> next(it) 'b' ->>> it.next() +>>> next(it) 'c' ->>> it.next() +>>> next(it) Traceback (most recent call last): File "<stdin>", line 1, in ? - it.next() + next(it) StopIteration \end{verbatim} Having seen the mechanics behind the iterator protocol, it is easy to add iterator behavior to your classes. Define a \method{__iter__()} method -which returns an object with a \method{next()} method. If the class defines -\method{next()}, then \method{__iter__()} can just return \code{self}: +which returns an object with a \method{__next__()} method. If the class defines +\method{__next__()}, then \method{__iter__()} can just return \code{self}: \begin{verbatim} class Reverse: @@ -4525,7 +4526,7 @@ class Reverse: self.index = len(data) def __iter__(self): return self - def next(self): + def __next__(self): if self.index == 0: raise StopIteration self.index = self.index - 1 @@ -4545,7 +4546,7 @@ s Generators are a simple and powerful tool for creating iterators. They are written like regular functions but use the \keyword{yield} statement whenever -they want to return data. Each time \method{next()} is called, the +they want to return data. Each time \function{next()} is called on it, the generator resumes where it left-off (it remembers all the data values and which statement was last executed). An example shows that generators can be trivially easy to create: @@ -4566,7 +4567,7 @@ g Anything that can be done with generators can also be done with class based iterators as described in the previous section. What makes generators so -compact is that the \method{__iter__()} and \method{next()} methods are +compact is that the \method{__iter__()} and \method{__next__()} methods are created automatically. Another key feature is that the local variables and execution state |