Vlookup in Python (other than JOIN)

If you want to handle everything in Python (instead of using SQL or Excel), there are many vlookup possibilities in python. Here I want to show the one I used in Boston Crime Data.

I wanted to group many crime definitions to decrease the number of categories in a new "offense description" column. For example instead of having "property damage", "auto theft", "larceny - all others" categories seperately, I wanted to group those crimes in one "theft-damage" category.

I created a new df with two columns, namely "Offense_Description" and "Offense_Category". The first column included all unique values of the offense description and the second one regrouped them in new categories.

Then I used ".map" method to act as the vlookup in excel and create a new column in the dataferame. I am adding this here, because at times merge or join functions do not work as well as expected and this may be a nice option to keep in mind. Here is how it looks:

Another example with .merge method (while converting the district codes to district names):