Pandas 5 Combining 2+ DF

Question 1

How to join two or more tables in Pandas

Answer 1

pd.merge(DF1, DF2[[‘DF2_C1’, ’DF2_C2’, ’etc’]], on = ‘gameid’)

This creates DF with all columns from DF1, and selected columns from DF2

The “on” keyword is option. If left out the default behavior to join on the columns the two DFs have in common

Or create new DF to merge with the columns of interest:
DF1 = DFa[[‘gameid’, ‘playerid’, ‘rush yds’]]
DF2 - DFb[[‘gameid’, ‘playerid’, ‘rec yds’]]

NewDF = pd.merge(DF1, DF2, on = [‘playerid’, ‘gameid’])

Question 2

How to designate left or right join in Pandas

Answer 2

Keyword is “how”

pd.merge(DF1, DF2, how = ‘left’, indicator=True)

Keyword “indicator” creates a column _merge which shows whether the observation was in the left, right, or both DF

NewDF[‘_merge’].value_counts()
right only 813
both 355
left only 200