human
keep only rows in a column matching a value in.
assistant
Here is a Python program to keep only rows in a column matching a value in the column

import pandas as pd

def keep_rows_in_column_matching_value(column, value):
    """Keep only rows in a column matching a value in ``column``.

    """
    return [row for row in column if row == value]

# Enter the dataframe
df = pd.DataFrame({"col1": ["a", "b", "c", "d", "e"], "col2": ["1", "2", "3", "4", "5"]})

# Calling the function
df_filtered = keep_rows_in_column_matching_value(df["col1"], "a")

#Remember to inspect code for bugs.