Question

我正在研究具有很多功能的大型有限元分析代码。为了在不同函数之间传递变量，我使用了python的kwargs。我主要选择这个，这样我就可以用很多不同的方式调用这些函数，从而创造了很大的灵活性。

但是现在我正在处理一个问题。从主函数我使用kwargs调用另一个函数。然后，第二个函数处理输入并添加新的kwargs。问题是在第一个中无法访问在该函数中创建的新kwargs。有这样做的pythonic方式吗？我创建了以下代码作为示例：

# Create main function
def main(**kwargs):
    # Add a key word argument
    kwargs["textMain"] = "text added in main"

    # Call a function with existing kwargs and a new one
    functionA(textNew = "text added in new" ,**kwargs)

    # Test what is in kwargs after subfunction is called
    print("\nTest kwargs after subfunction is called:")

    if "textMain" in kwargs:
        print(kwargs["textMain"])

    if "textNew" in kwargs:
        print(kwargs["textNew"])

    if "textA" in kwargs:
        print(kwargs["textA"])

def functionA(**kwargs):

    # Test kwargs before adding kwargs in subfunction
    print("\nTest kwargs in subfunction before adding:")

    if "textMain" in kwargs:
        print(kwargs["textMain"])

    if "textNew" in kwargs:
        print(kwargs["textNew"])

    if "textA" in kwargs:
        print(kwargs["textA"])

    # Add kwargs
    kwargs["textA"] = "text added in sub A"

    # and test kwargs again
    print("\nTest kwargs in subfunction after adding:")
    if "textMain" in kwargs:
        print(kwargs["textMain"])

    if "textNew" in kwargs:
        print(kwargs["textNew"])

    if "textA" in kwargs:
        print(kwargs["textA"])

if __name__ == "__main__":
    main()

这会产生以下输出：

#Test kwargs in subfunction before adding:
#text added in main
#text added in new

#Test kwargs in subfunction after adding:
#text added in main
#text added in new
#text added in sub A

#Test kwargs after subfunction is called:
#text added in main

我喜欢的输出是：

#Test kwargs in subfunction before adding:
#text added in main
#text added in new

#Test kwargs in subfunction after adding:
#text added in main
#text added in new
#text added in sub A

#Test kwargs after subfunction is called:
#text added in main
#text added in new
#text added in sub A

如果任何人能解决我的问题，那将是非常有帮助的。提前谢谢！

Answer 1

在调用表达式中使用**kwargs语法时，Python会扩展字典并传入单独的参数。然后，函数签名中的相同语法告诉Python在该函数中创建 new 字典以捕获关键字参数。

换句话说，kwargs中的main()与functionA()中的字典不是同一个字典。

传入实际字典（不使用**kwargs语法）或让functionA()返回新字典。

作为单个参数传入kwargs，您可以从functionA()更改字典，并查看main()中反映的更改，因为它们现在共享对同一字典的引用：

def main(**kwargs):
    functionA(kwargs, textNew="text added in new")
    # ... etc ...


def functionA(mapping, **kwargs):
    # do something with mapping, it is the same dictionary as kwargs in main

从kwargs返回更新的functionA()字典要求您将新对象重新分配回kwargs中的main()：

def main(**kwargs):
    kwargs = functionA(textNew="text added in new", **kwargs)
    # ... etc ...

def functionA(**kwargs):
    # ...
    return kwargs

如何使用python访问在其他函数中创建的kwargs？

1 个答案: