Pandas Concatenate and Merge: Combining DataFrames into One

To concatenate or merge all dataframes rows into one dataframe using pandas, you can use the following code:

Concatenating dataframes:

import pandas as pd

# create dataframes with different data
df1 = pd.DataFrame({'A': [1, 2, 3], 'B': [4, 5, 6]})
df2 = pd.DataFrame({'A': [4, 5, 6], 'B': [7, 8, 9]})
df3 = pd.DataFrame({'A': [7, 8, 9], 'B': [10, 11, 12]})

# concatenate dataframes
result = pd.concat([df1, df2, df3])

# print result
print(result)

Output:

   A   B
0  1   4
1  2   5
2  3   6
0  4   7
1  5   8
2  6   9
0  7  10
1  8  11
2  9  12

Merging dataframes:

import pandas as pd

# create dataframes with different data
df1 = pd.DataFrame({'A': [1, 2, 3], 'B': [4, 5, 6]})
df2 = pd.DataFrame({'A': [2, 3, 4], 'C': [7, 8, 9]})
df3 = pd.DataFrame({'A': [3, 4, 5], 'D': [10, 11, 12]})

# merge dataframes
result = pd.merge(df1, df2, on='A', how='outer')
result = pd.merge(result, df3, on='A', how='outer')

# print result
print(result)

Output:

   A    B    C     D
0  1.0  4.0  NaN   NaN
1  2.0  5.0  7.0   NaN
2  3.0  6.0  8.0  10.0
3  4.0  NaN  9.0  11.0
4  5.0  NaN  NaN  12.0