根据df1中的3个值与df2中的3个值匹配，在数据框中填充新列

Question

Let's say I have 2 data frames, both share the columns " shoe ", " size ", and " color ". The smaller data frame contains each shoe model and has a column " price ". The larger data frame contains every sold shoe but doesn't contain price (doesn't make sense I know but I'm just trying to explain my issue)

I'd like to find a way to compile a new column for shoe price in the larger data frame, which will take the shoe price from the smaller data frame for every match of the 3 shared columns " shoe ", " size " and " color ".

I've tried merges which don't work due to the different sizes, I've tried using a for loop but honestly, I'm still a beginner.

Can anyone point me in the right direction?

Here's some code to generate dataframes with random data:

def Rand(start, end, num): 
res = [] 

for j in range(num): 
    res.append(random.randint(start, end)) 

return res


df1 = pd.DataFrame({"shoe":range(10), 
"size":range(1,11),"color":range(2,12),
'price':range(100,110)})

df2 = pd.DataFrame({"shoe": Rand(1, 10, 100),
"size": Rand(1, 11, 100), "color": Rand(1, 11, 100)})

Given the above dataframes, I'm trying to create a 'price' column in df2 that is found by matching df2's columns with matching values in the corresponding columns in df1

Answer 1

Maybe you need this:

import pandas as pd
file1 = pd.DataFrame({"shoe":range(10), "size":range(1,11),"color":range(2,12), 'price':range(100,110)})
file2 = pd.DataFrame({"shoe":range(100), "size":range(1,101),"color":range(2,102)})
df = pd.merge(file1,file2,how='right', on = ["shoe","size","color"])
df.head()

In this example you will get new dataframe, which merge matching three columns. You can read more here https://pandas.pydata.org/pandas-docs/stable/merging.html