Vlookup/Map value from one dataframe to another dataframe in Python

Question

I want to do something similar to the vlookup in the python. Here is a dataframe I want to lookup for value 'Flow_Rate_Lupa'

And here is the dataframe I want to fill the data by looking at the same month+day to fill the missing value. Is there any one to help me to solve how to do this QAQ enter image description here

Lara Amro · Accepted Answer · 2021-01-13 07:44:59Z

2

I usually merge the two data frames and define an indicator, then filter out the values where the indicator says both meaning data is in both data frames.

import pandas as pd

mergedData= pd.merge(df1,df2, how='left' ,left_on='Key1', right_on='Key2', indicator ='Exists')
filteredData = mergedData[mergedData[Exists]='both']

edited Jan 13, 2021 at 7:44

answered Jan 12, 2021 at 10:35

Lara Amro

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jezrael · Accepted Answer · 2021-01-12 10:27:13Z

1

Use DataFrame.merge with left join and the nreplace missing values by Series.fillna with DataFrame.pop for use and remove column:

df = df2.merge(df1, on=['month','day'], how='left', suffixes=('','_'))
df['Flow_Rate_Lupa'] = df['Flow_Rate_Lupa'].fillna(df.pop('Flow_Rate_Lupa_'))

answered Jan 12, 2021 at 10:27

jezrael

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