Question

Describe what the following module is doing:

c = start
while True:
value = yield c
if value != None:
c = value
         else:
            c += 1

Answer 1

This defines a generator that produces a sequence of values beginning with start.

• The first next() returns start.
• If a value is sent using send(value), the generator replaces c with that value.
• If None is sent, or ordinary next() is used, c is increased by one.
• It continues indefinitely until the generator is closed.

Example:

def test(start=0):
    c = start
    while True:
        value = yield c
        if value is not None:
            c = value
        else:
            c += 1


g = test(5)
print(next(g))       # 5
print(next(g))       # 6
print(g.send(20))    # 20
print(next(g))       # 21