How can the DataFrame index be expanded or enlarged?

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The DataFrame index can be expanded or enlarged by adding new rows to the DataFrame using the loc or append method.

Using loc method to add new rows:

import pandas as pd

df = pd.DataFrame({'A': [1, 2, 3], 'B': [4, 5, 6]}, index=['row1', 'row2', 'row3'])
print(df)

# Output:
#       A  B
# row1  1  4
# row2  2  5
# row3  3  6

# Adding new rows to the DataFrame using loc method
df.loc['row4'] = [7, 8]  
df.loc['row5'] = [9, 10]

print(df)

# Output:
#        A   B
# row1   1   4
# row2   2   5
# row3   3   6
# row4   7   8
# row5   9  10

Using append method to add new rows:

import pandas as pd

df = pd.DataFrame({'A': [1, 2, 3], 'B': [4, 5, 6]}, index=['row1', 'row2', 'row3'])
print(df)

# Output:
#       A  B
# row1  1  4
# row2  2  5
# row3  3  6

# Adding new rows to the DataFrame using append method
new_data = {'A': [7, 8], 'B': [9, 10]}
new_df = pd.DataFrame(new_data, index=['row4', 'row5'])
df = df.append(new_df)

print(df)

# Output:
#        A   B
# row1   1   4
# row2   2   5
# row3   3   6
# row4   7   9
# row5   8  10

Both of these methods allow us to expand or enlarge the index of a DataFrame by adding new rows.