如何跨python函数累积添加?

不要重新分配 inventory 在你的功能,但使用它的方法!

那么它仍然是对同一个的引用

def add_fruit(inventory, fruit, quantity=0):
    inventory[fruit] = inventory.get(fruit, 0) + quantity

>>> new_inventory = {}
>>> add_fruit(new_inventory,'strawberry',10)
>>> add_fruit(new_inventory,'strawberry',90)
>>> new_inventory
{'strawberry': 100}

下面是一个更完整的例子

>>> def foo(value):
...     print(f"initial value: {id(value)}")
...     value["a"] = 1     # mutate original dict
...     print(f"mutated value: {id(value)}")
...     value = {"b": 2}   # re-use the name for another ref
...     print(f"changed name:  {id(value)}")
... 
>>> input_value = {}
>>> foo(input_value)       # the id() calls show value differs!
initial value: 132972815809856
mutated value: 132972815809856
changed name:  132972815874112
>>> input_value            # only the original reference is changed!
{'a': 1}

尽管使用 inventory 在这个特定的用例中,为了保持 add_fruit 更具活力&不管怎样,我会把它放在里面的。

因此,你可以尝试:

new_inventory = {}

def add_fruit(inventory, fruit, quantity=0):
    if fruit not in inventory.keys():
        inventory[fruit] = quantity
    else:
        inventory[fruit] += quantity

add_fruit(new_inventory, "strawberry", 10)
add_fruit(new_inventory, "strawberry", 90)

print(new_inventory) # {'strawberry': 100}