[英]Passing function parameter name to another function in Python
Given a simple function: 给出一个简单的函数:
def A(a = 1, b = 2):
return a+b
I want to write another function to change the default parameter value, for either a
or b
. 我想编写另一个函数来更改
a
或b
的默认参数值。 And user can specify the parameter to change by setting var = a
or var = b
. 用户可以通过设置
var = a
或var = b
来指定要更改的参数。 For example: 例如:
def B(var = 'a', new_value = 10):
temp_dict = {var:new_value}
ans = A(var)
return ans
or 要么
def B(var = 'a', new_value = 10):
ans = A(var = new_value)
return ans
In function def B()
, after setting var = a
and var = new_value = 10
, I expect A(var = new_value)
to achieve the same effect as A(a = 10)
. 在函数
def B()
,设置var = a
和var = new_value = 10
,我期望A(var = new_value)
可以达到与A(a = 10)
相同的效果。 Do you know the correct way to write function def B()
? 您知道编写函数
def B()
的正确方法吗? Thanks. 谢谢。
You are almost there. 你快到了 From your
B()
function, while making the call to A()
, you need to unpack the temp_dict
and pass it as an argument to A()
. 通过
B()
函数,在调用A()
,需要解压缩temp_dict
并将其作为参数传递给A()
。 See below: 见下文:
>>> def A(a = 1, b = 2):
... return a+b
...
>>> def B(var = 'a', new_value = 10):
... temp_dict = {var:new_value}
... ans = A(**temp_dict)
# ^ unpack the dict, and pass it as an argument
... return ans
...
>>> B()
12
For more details on how this **
works with a dict, please take a look at: 有关此
**
如何与字典配合使用的更多详细信息,请查看:
I took the liberty of interpreting a bit what the OP said he wanted, ie change the default parameter value, for either a or b . 我可以随意解释OP想要的内容,即更改a或b的默认参数值 。 So what I did was to return a transformed function A with either the a or b defaults changed via a partial:
所以我要做的是返回转换后的函数A,其中a或b的默认值都通过部分更改:
from functools import partial
def B3(var ="a", new_value=10):
return partial(A, **{var:new_value})
sample outputs: 样本输出:
(Pdb) f = B3("a",10)
(Pdb) f()
12
(Pdb) f = B3("b",10)
(Pdb) f()
11
(Pdb) f(a=10)
20
(Pdb) f(b=13)
14
(Pdb) f(a=5,b=5)
10
That is different from the 2nd half of the request however, that of having something based on B(var="a",new_value=10)
as function signature. 但是,与请求的第二部分不同,该请求具有基于
B(var="a",new_value=10)
作为函数签名。
The only thing is, it chokes happily if you don't use keyword parameters: 唯一的事情是,如果您不使用关键字参数,它会令人窒息:
(Pdb) f(7,7)
*** TypeError: A() got multiple values for keyword argument 'b'
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