python - Keep one column in df2 based on value in df1

Question

Suppose I have two dataframes:

data = {'model':  ['B']}
df1 = pd.DataFrame (data, columns = ['model'])
df1

data = {'A':  ['0.55', '0.49', '0.47',],
        'B': ['0.48', '0.53', '0.54'],
        'C': ['0.50', '0.51', '0.45']}
df2 = pd.DataFrame (data, columns = ['A', 'B', 'C'])
df2

I would like df2 to keep only the column where the name is equal to the value in df1. So the output would be that df2 only has one column in the dataframe - 'B'

How would I do this?

Thanks

Answer 1

You can do:

import pandas as pd
data = {'model':  ['B']}
df1 = pd.DataFrame (data, columns = ['model'])
data = {'A':  ['0.55', '0.49', '0.47',],
        'B': ['0.48', '0.53', '0.54'],
        'C': ['0.50', '0.51', '0.45']}
df2 = pd.DataFrame (data, columns = ['A', 'B', 'C'])
outdf = df2[df1['model']]  # alternatively: outdf = df2[df1.model]
print(outdf)

Output:

      B
0  0.48
1  0.53
2  0.54

Explanation: we can use [] (getitem) to get certain columns from pandas.DataFrame by using iterable - in this case it is pandas.Series (column) from df1 named model.