Unable to join pandas dataframe on string type

问题内容：

I have two DataFrames objects whose columns are as below

Dataframe 1:

df.dtypes

Output:

ImageID       object
Source        object
LabelName     object
Confidence     int64
dtype: object

Dataframe 2:

a.dtypes

Output:

LabelName       object
ReadableName    object
dtype: object

Here, i am trying to combine these two dataframes as below

combined =  df.join(a,on='LabelName')

But, i am getting the following error

ValueError: You are trying to merge on object and int64 columns. If you wish
to proceed you should use pd.concat

But, i am merging them on LabelName, which has only strings (object datatype)

Am i missing something here?

问题答案：

About the on parameter, the documentation says:

Column or index level name(s) in the caller to join on the index in other,
otherwise joins index-on-index.

Note that join() always uses other.index. You can try this:

df.join(a.set_index('LabelName'), on='LabelName')

Or use df.merge() instead.