Python Panda

What is the most efficient way to loop through dataframes with pandas?
I want to perform my own complex operations on financial data in dataframes in a sequential manner. For example I am using the following MSFT CSV file taken from Yahoo Finance: Date,Open,High,Low...
Efficiently iterating over rows in a Pandas DataFrame
Never use iterrows and itertuples again

locate specific row:
Either we know the index
Either https://pandas.pydata.org/pandas-docs/stable/reference/api/pandas.Series.str.fullmatch.html?highlight=fullmatc#pandas.Series.str.fullmatch