Python:ufunc'add'不包含签名匹配类型为dtype('S21')dtype('S21')dtype('S21')的循环 [英] Python: ufunc 'add' did not contain a loop with signature matching types dtype('S21') dtype('S21') dtype('S21')

问题描述

我有两个数据帧，它们都有一个Order ID和date.

I have two dataframes, which both have an Order ID and a date.

我想在第一个数据帧df1中添加一个标志:如果在数据帧df2中有一个具有相同order id和date的记录，则添加一个Y:

I wanted to add a flag into the first dataframe df1: if a record with the same order id and date is in dataframe df2, then add a Y:

[ df1['R'] = np.where(orders['key'].isin(df2['key']), 'Y', 0)]

要做到这一点，我将创建一个键，该键将是order_id和date的串联，但是当我尝试以下代码时:

To accomplish that, I was going to create a key, which would be the concatenation of the order_id and date, but when I try the following code:

df1['key']=df1['Order_ID']+'_'+df1['Date']

我收到此错误

ufunc 'add' did not contain a loop with signature matching types dtype('S21') dtype('S21') dtype('S21')

df1看起来像这样:

df1 looks like this:

Date | Order_ID | other data points ... 
201751 4395674  ...
201762 3487535  ...

这些是数据类型:

df1.info()
RangeIndex: 157443 entries, 0 to 157442
Data columns (total 6 columns):
Order_ID                                 157429 non-null object
Date                                     157443 non-null int64
...
dtypes: float64(2), int64(2), object(2)
memory usage: 7.2+ MB

df1['Order_ID'].values
array(['782833030', '782834969', '782836416', ..., '783678018',
       '783679806', '783679874'], dtype=object)

推荐答案

问题是您无法将对象数组(包含字符串)添加到数字数组中，这是模棱两可的:

The problem is that you can't add an object array (containing strings) to a number array, that's just ambiguous:

>>> import pandas as pd

>>> pd.Series(['abc', 'def']) + pd.Series([1, 2])
TypeError: ufunc 'add' did not contain a loop with signature matching types dtype('<U21') dtype('<U21') dtype('<U21')

您需要将Dates明确转换为str.

我不知道如何在熊猫中有效地做到这一点，但是您可以使用:

I don't know how to do that efficiently in pandas but you can use:

df1['key'] = df1['Order_ID'] + '_' + df1['Date'].apply(str)  # .apply(str) is new

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