Key error when combining pandas (left join)

Question

I have two data frames below, df_purchase (1) and df_login (2)

+--------+-----+--------+------------+--------------------+-------------+--------------------------+ | | age | gender | ttp | count | sum(amount) | region | +--------+-----+--------+------------+--------------------+-------------+--------------------------+ | 49427 | 63 | M | 824.731412 | 2 | 25.00 | Omaha, Nebraska | | 28433 | 49 | M | 1.166250 | 2 | 41.94 | Catasauqua, Pennsylvania | | 4162 | 29 | M | 5.620949 | 2 | 51.78 | Eagle Center, Iowa | | 18747 | 43 | M | 153.502072 | 2 | 23.84 | Pacific, Washington | | 45173 | 59 | M | 0.027257 | 2 | 13.98 | De Soto, Missouri | +--------+-----+--------+------------+--------------------+-------------+--------------------------+ +--------+-----+--------+------------+--------------------+-------------+--------------------------+ | | age | gender | count | region | | | | 671766 | 84 | M | 13900 | New York, New York | | | | 671166 | 84 | F | 7619 | New York, New York | | | | 672209 | 85 | F | 6483 | New York, New York | | | | 672671 | 85 | M | 5808 | New York, New York | | | | 195201 | 34 | M | 3817 | New York, New York | | | +--------+-----+--------+------------+--------------------+-------------+--------------------------+ 

I am trying to join df_logins to df_purchase by age, gender and region with the following pandas code:

 df = pd.merge(df_purchase, df_login[['count']], how='left', on=['age', 'gender', 'region']) 

However, I keep getting this error: KeyError: 'age' Any thoughts?

Answer 1

From this, a KeyError arises:

 df = pd.merge(df_purchase, df_login[['count']] <- this selects just count column, how='left', on=['age', 'gender', 'region']) 

You have selected only one column from df_login , you need it:

 df = pd.merge(df_purchase, df_login, how='left', on=['age', 'gender', 'region']) 

I assume that this is not your complete data, since you do not have common values ​​in the age and region column in df_login .