What does the 'index_col' parameter do in the 'read_csv' function?

The index_col parameter in the read_csv function specifies which column(s) to use as the row labels of the DataFrame. By default, pandas assigns a numeric index to the rows, but you can set index_col to one or more column names or indices to use those columns as the index instead.

For example:

import pandas as pd

# Using the first column as the index
df = pd.read_csv('data.csv', index_col=0)

In this case, the first column of the CSV file will be used as the index for the DataFrame. You can also specify multiple columns by passing a list:

df = pd.read_csv('data.csv', index_col=[0, 1])  # Using the first and second columns as a multi-index

This allows for more meaningful indexing of the DataFrame based on the data in the specified columns.