def fun1():

    '''the function instruction'''

    x-=1

    return x

def fib(n):

    """Print a Fibconacci series up to n"""  #对此函数的解释说明

    a,b = 0,1

    while a<n:

        print(a,end=' ')

        a,b=b,a+b

    print()

fib(2000)

#结果

0 1 1 2 3 5 8 13 21 34 55 89 144 233 377 610 987 1597

#函数

def func1():

    """test1"""

    print("It's func1")

    return 1

#过程

def func2():

    """test2"""

    print("It's func2")

func1()

func2()

print("----------------")

print(func1())

print(func2())

#测试结果：

It's func1

It's func2

----------------

It's func1

1

It's func2

None