python print inside vs outside function?

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What does the “yield” keyword do? 36 answers

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In your code fibon is a generator function. And when you call it returns generator object. You could remove yield from function

def fibon(n):
    a = b = 1
    for i in range(n):
        a, b = b, a + b
        print(a)  # move here inside function but doesnt print?

fibon(20)

or construct list from generator object

def fibon(n):
    a = b = 1
    for i in range(n):
        yield a
        a, b = b, a + b
        print(a)  # move here inside function but doesnt print?

list(fibon(20))

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The yield statement makes the function returns a generator object , not just a function.

In short, python generators are iterators. PEP 255 that describes simple generators. Generators are used either by calling the next method on the generator object or using the generator object in a for loop.

To execute the generator, you need to iterate over it. So, for x in fibon(20) does the iteration, while fibon(20) returns a generator object.

def fibon(n):
       a = b = 1
       for i in range(n):
           yield a
           a, b = b, a + b
fibon(5)
<generator object fibon at 0x00000000034A6A20>

for i in fibon(5):
    print i

# list() can be used too, because it accepts generator as a param
fibos = list(fibon(5))

If you just change the yield statement to print , you get regular function. But I wouldn't recommend that with fibonacci, the yield option is the way to go.

>>> fibon
<function fibon at 0x0000000002D31C88>

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如果目标只是打印数字，只要用print替换yield就足够了。

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