传递多个参数以应用（Python） [英] Passing multiple arguments to apply (Python)

问题描述

我正在清理Python中的一些代码来向量化一组功能，我想知道是否有一个很好的方法来使用apply来传递多个参数。考虑以下（当前版本）：

I'm trying to clean up some code in Python to vectorize a set of features and I'm wondering if there's a good way to use apply to pass multiple arguments. Consider the following (current version):

def function_1(x):
    if "string" in x:
        return 1
    else:
        return 0

df['newFeature'] = df['oldFeature'].apply(function_1)

使用上面我不得不编写一个新的函数（function_1，function_2等）来测试每个子串string我想查找。在一个理想的世界中，我可以组合所有这些冗余的函数，并使用这样的东西：

With the above I'm having to write a new function (function_1, function_2, etc) to test for each substring "string" that I want to find. In an ideal world I could combine all of these redundant functions and use something like this:

def function(x, string):
    if string in x:
        return 1
    else:
        return 0

df['newFeature'] = df['existingFeature'].apply(function("string"))

但尝试返回错误 TypeError ：function（）只需要2个参数（1个给定）有另一种方法来完成同样的事情吗？

But trying that returns the error TypeError: function() takes exactly 2 arguments (1 given) Is there another way to accomplish the same thing?

def function(string, x):
    if string in x:
        return 1
    else:
        return 0

df['newFeature'] = df['oldFeature'].apply(partial(function, 'string'))

推荐答案

我相信你想要 functools.partial 。演示：

I believe you want functools.partial. A demo:

>>> from functools import partial
>>> def mult(a, b):
...     return a * b
...
>>> doubler = partial(mult, 2)
>>> doubler(4)
8

在你的情况下，你需要交换 function （因为 partial 的想法），然后只是

In your case you need to swap arguments in function (because of idea of partial), and then just

df['existingFeature'].apply(partial(function, "string"))

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