How to move data from one dataframe to another based on matching column values with pandas?

Question

I have two pandas DataFrames containing differently ordered data, and I am trying to move data from one to the other based on content. I've tried a lambda function, but I don't think I'm understanding how this is supposed to work. Here are simplified versions of my data:

df1 = 
   Name  Pos  Opponent  DPAvPos
1  Dave  QB   DEN       NaN
2  Bill  QB   GB        NaN
3  Sean  QB   DET       NaN

df2 =
   Name  DKP/Game
1  DET   20.1
2  DEN   10.4
3  GB    15.2

I would like to move data from the DKP/Game column of df2 to the DPAvPos column df1 by matching data from the Opponent column of df1 with the Name column of df2. So far everything I've tried hasn't worked.

Answer 1

You could try to merge these two dataframes, then drop DPAvPos and rename DKP/Game as DPAvPos :

import pandas as pd

df1 = pd.DataFrame({
    "Name" : ["Dave", "Bill", "Sean"],
    "Pos" : ['QB', 'QB', 'QB'],
    "Opponent" : ["DEN", "GB", "DET"],
    "DPAvPos": ["NaN", "NaN", "NaN"]
})

df2 = pd.DataFrame({
    "Name" : ["DET", "DEN", "GB"],
    "DKP/Game" : [ 20.1, 23, 21]
})

df2.rename(columns={"Name" : "Opponent"}, inplace=True)
df3 = pd.merge(df1, df2, on="Opponent")
df3.drop('DPAvPos', axis=1, inplace=True)
df3.rename(columns={"DKP/Game" : "DPAvPos"}, inplace=True)