modern pandas 3 - merge impossible

[mackinpuff]

The merge (many-to-one) at the end of the third notebook results in an empty data frame, because the weather data is for 2014 and the flights data for 2017. Your results show flight data for 2014, so I imagine you may be using a different dataset.

This may also have to do with the source data being changed; I also noticed that the underscores are removed from the flight data set, e.g. fl_date has become flightdate and unique_carrier has become uniquecarrier.

p.s. Thanks for sharing your well-written code and insights into pandas, they are a very welcome and useful read!