Python：ufunc 'add' 不包含签名匹配类型 dtype('S21') dtype('S21') dtype('S21') 的循环
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Python: ufunc 'add' did not contain a loop with signature matching types dtype('S21') dtype('S21') dtype('S21')
提问by jeangelj
I have two dataframes, which both have an Order IDand a date.
我有两个数据框，它们都有一个Order ID和一个date.
I wanted to add a flag into the first dataframe df1: if a record with the same order idand dateis in dataframe df2, then add a Y:
我想在第一个数据帧中添加一个标志df1：如果具有相同order id且date位于数据帧中的记录df2，则添加一个Y：
[ df1['R'] = np.where(orders['key'].isin(df2['key']), 'Y', 0)]
To accomplish that, I was going to create a key, which would be the concatenation of the order_idand date, but when I try the following code:
为了实现这一点，我将创建一个键，它是order_idand的连接date，但是当我尝试以下代码时：
df1['key']=df1['Order_ID']+'_'+df1['Date']
I get this error
我收到这个错误
ufunc 'add' did not contain a loop with signature matching types dtype('S21') dtype('S21') dtype('S21')
df1 looks like this:
df1 看起来像这样：
Date | Order_ID | other data points ...
201751 4395674 ...
201762 3487535 ...
These are the datatypes:
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)
回答by MSeifert
The problem is that you can't add an object array (containing strings) to a number array, that's just ambiguous:
问题是您不能将对象数组（包含字符串）添加到数字数组中，这很不明确：
>>> 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')
You need to explicitly convert your Datesto str.
您需要明确地将您Dates的str.
I don't know how to do that efficiently in pandas but you can use:
我不知道如何在 Pandas 中有效地做到这一点，但您可以使用：
df1['key'] = df1['Order_ID'] + '_' + df1['Date'].apply(str) # .apply(str) is new
