join of two dataframes in pandas code example

Example 1: pandas left join

df.merge(df2, left_on = "doc_id", right_on = "doc_num", how = "left")

Example 2: pandas merge multiple dataframes

import pandas as pd
from functools import reduce

# compile the list of dataframes you want to merge
data_frames = [df1, df2, df3]
df_merged = reduce(lambda  left,right: pd.merge(left,right,on=['key_col'],
                                            how='outer'), data_frames)

Example 3: how to join two dataframe in pandas based on two column

merged_df = left_df.merge(right_df, how='inner', left_on=["A", "B"], right_on=["A2","B2"])