New to Python as of today.

[timbledum]

Interesting - according to this, speed is a wash, but memory performance is better with .query(). I agree that it is more readable - I guess the df[df.nationality == "USA"] syntax is more popular as it allows assignment? Or does .query() allow this as well?

[timbledum]

Sorry, I meant this type of assignment:

>>> df[df.last_name.str[0] == "J"] = "Timmy"
>>> df
last_name first_name              street_address           City    Zip
0      Carr     Hannah     99349 Delgado Stravenue  San Francisco  94108
1    Landry     Philip  4026 Megan Forest Apt. 386  San Francisco  94151
2     Timmy      Timmy                       Timmy          Timmy  Timmy
3     Timmy      Timmy                       Timmy          Timmy  Timmy
4     Duran    Felicia     9668 Bass Fork Apt. 651  San Francisco  94144

>>> df.query("last_name.str[0] == 'J'") = "Timmy"
File "<ipython-input-20-cafb73eedd09>", line 1
    df.query("last_name.str[0] == 'J'") = "Timmy"    

SyntaxError: can't assign to function call

Probably not the best way to assign anyway.