Precautions for function default parameters (formal parameter angle)

#  Parameter angle , When the default parameter is a variable data type , Need attention 
#  If the default parameter points to a variable data type , No matter how many times this default parameter is called , All point to the same 
#  Create a new memory in the memory to store the list , Does not end with function , Memory disappears （ Here's the picture ）
def func(name, lis=[]):
    lis.append(name)
    return lis
print(func('hello'))  # ['hello']
print(func('ait'))   # ['hello', 'ait']


def func1(num, l=[]):
    l.append(num)
    return l

print(func1(15))    # 15
print(func1(17, []))    # 17
print(func1(20))    # [15, 20]


def func2(num, l=[]):
    l.append(num)
    return l
ret1 = func2(15)
ret2 = func2(17, [])
ret3 = func2(20)
print(ret1)    # [15, 20]
print(ret2)    # 17
print(ret3)    # [15, 20]

The memory space with variable data type as the default parameter will not disappear with the end of the function , Here's the picture .