Python 2-1 function parameters

One, function definition

def function name (parameter list):

    Function body

Find the sum of natural numbers within 100

# 求 100 之内自然数的和
# 方法一：内置 sum 函数
n = 100
print(sum(range(1, n+1)))

# 方法二：for循环
s = 0
for i in range(1, n+1):
    s += i
print(s)

# 方法：自定义函数
def f(n):
    '''
        求 100 以内的自然数的和 # 这里是函数的说明文档，doc的位置
        :param lis: n 是自然数 # 参数列表的说明
        :return: 和 # 返回值的说明
    '''
    s = 0
    for i in range(1, n+1):
        s += i
    
    return s

print(f(100))
print(f.__doc__)

The return [expression] statement is used to exit a function and optionally return an expression to the caller.

The return statement without parameter values ​​or the default return returns None.

Return multiple values ​​will be automatically packed into a tuple, receiving can use multiple variables (unpacking) can also use a variable (tuple)