将方法列表中的方法应用于 pandas 数据框 [英] Apply a method from a list of methods to pandas dataframe

问题描述

这是我的第一个问题，请耐心等待.

this is my first question here so please be patient with me.

我的问题如下:

假设我们有一个pandas数据框，我们想将一些pd.Series方法动态地应用于此数据框的一组列.为什么下面的示例不起作用?

Assume we have a pandas Dataframe and we want to apply dynamically some pd.Series methods to a set of columns of this Dataframe. Why the following example doesn't work?

testframe=pd.DataFrame.from_dict({'col1': [1,2] ,'col2': [3,4] })
funcdict={'col1':[pd.Series.astype,str.replace],'col2':[pd.Series.astype,str.replace]}
argdict= {'col1':[['str'],['1','A']],'col2':[['str'],['3','B']]}

for col in testframe.columns:
    for func in funcdict[col]:
            idx=funcdict[col].index(func)
            testframe[col]=testframe[col].func(*argdict[col][idx])

预期结果将是

  col1 col2
0  'A'  'B'
1  '1'  '4'

但是我却得到了

AttributeError: 'Series' object has no attribute 'func'

非常

testframe['col1']=testframe['col1'].astype(*argdict['col1'][0])

可以按预期工作，因此尽管存在

works as expected, so somehow python seems to have a problem with the '.func' syntax despite the fact that

print(func)

产生所需的输出:函数NDFrame.astype at 0x00000186954EB840"等.

yields the desired output: 'function NDFrame.astype at 0x00000186954EB840' etc.

推荐答案

您调用方法的语法不正确.您可以通过两种方法在Python中调用方法.

Your syntax for calling a method is incorrect. There are 2 ways you can call a method in Python.

直接

如您所见，这将起作用.请注意，astype并未引用其他对象，它是属于pd.Series的方法的实际名称.

As you found, this will work. Note that astype isn't referencing some other object, it's the actual name of the method belonging to pd.Series.

testframe['col1'] = testframe['col1'].astype(*argdict['col1'][0])

功能性

该功能方法明确表明astype是该方法的名称.

The functional method demonstrates explicitly that astype is the name of the method.

from operator import methodcaller

testframe['col1'] = methodcaller('astype', *argdict['col1'][0])(testframe[col])

尝试testframe[col].func(...)永远不会起作用，因为func不是pd.Series方法的名称.

Trying testframe[col].func(...) will never work as func is not the name of a pd.Series method.

这篇关于将方法列表中的方法应用于 pandas 数据框的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！