生成器的使用demo

定义一个函数：

def frange(start, stop, increment):
    x = start
    while x < stop:
        yield x
        x += increment

使用：

>>> for n in frange(, , 0.5):
...     print(n)
...

0.5
1.0
1.5
2.0
2.5
3.0
3.5
>>> list(frange(, , 0.125))
[, 0.125, 0.25, 0.375, 0.5, 0.625, 0.75, 0.875]
>>>

---

demo：

>>> def countdown(n):
...     print('Starting to count from', n)
...     while n > :
...         yield n
...         n -=
...     print('Done!')
...

>>> # Create the generator, notice no output appears
>>> c = countdown()
>>> c
<generator object countdown at 0x1006a0af0>

>>> # Run to first yield and emit a value
>>> next(c)
Starting to count from 

>>> # Run to the next yield
>>> next(c)

>>> # Run to next yield
>>> next(c)

>>> # Run to next yield (iteration stops)
>>> next(c)
Done!
Traceback (most recent call last):
    File "<stdin>", line , in <module>
StopIteration
>>>