Add a column to pandas dataframe based on value present in different dataframe

Question

I have 2 dataframes like the following (A and B):

     ID    color
0     5    red
1     6    blue
2     7    blue
3     8    NaN
4     9    green
5     10   NaN

     ID    characteristic
0     7    tall
1     9    short
2     24   short
3     1    tall
4     11   medium
5     10   tall

for each ID in df A I want to check if there is a corresponding ID in dataframe B . If there is a corresponding ID, then new column in df A should have the value True, and if not then False

The output should look like this:

     ID    color  df_b_presence
0     5    red    False
1     6    blue   False
2     7    blue   True
3     8    NaN    False
4     9    green  True
5     10   NaN    True

Answer 1

You can use .isin(), as follows:

A['df_b_presence'] = A['ID'].isin(B['ID'])

Result:

print(A)

    ID  color  df_b_presence
0   5    red          False
1   6   blue          False
2   7   blue           True
3   8    NaN          False
4   9  green           True
5  10    NaN           True