Amazing Python 1: "yield"

bingtuag

　　"yield" is used for Generater (below 2.2) or seperately (2.2 or above) in Python.

　　


　　"yield" mainly works as "return", but it makes a function able to have multiplereturn values step by step
.

　　All return values will comprise


a sequence which can be used in "for" or more amazingly as a
"link"
by running "link.next()"!


　　Example 1:


def generater():
yield 1
yield 2
yield 3
for i in generater():
print i,
print "\n"
print "getnerater() =", generater()
print "list(generater()) =", list(generater())
print
link = generater()
print "link.next() =", link.next()
print "link.next() =", link.next()
print "link.next() =", link.next()
　　
Output:


1 2 3
getnerater() = <generator object at 0xb7dafb0c>
list(generater()) = [1, 2, 3]
link.next() = 1
link.next() = 2
link.next() = 3

　　


　　Example2, calculating fibonacci(20):

　　(from speech "Object-oriented design with Python" by Bruce Eckel, 2005, http://us.pycon.org/talks/2005/wed/track1/44/talkDetails
)

def fibonacci(count):
def fib(n):
if n < 2: return 1
return fib(n-2) + fib(n-1)
n = 0
while n < count:
yield fib(n)
n += 1
for f in fibonacci(20): # Automatically iterable
print f,
　　Output:


1 1 2 3 5 8 13 21 34 55 89 144 233 377 610 987 1597 2584 4181 6765
　　Example3, let's forget about recursion!

　　(from "Dive into Python, e.g. 17.19")


def fibonacci(n):
a, b = 1, 1
for i in range(n):
yield a
a, b = b, a+b
for f in fibonacci(20):
print f,
　　Output:


1 1 2 3 5 8 13 21 34 55 89 144 233 377 610 987 1597 2584 4181 6765