What is the difference between these pieces of code?

Question

Python

Good day. I am studying the Pandas library in Yandex.Practice and ran into an incident.
The validator passes one solution, but not the other. I can not understand in connection with what, because the conclusion they seem to have is the same at first glance.
The first option works, but the second one doesn't.
Maybe they have something else difference, but I can not understand it?

import pandas as pd
df = pd.read_csv('music_log_upd.csv')

#1 вариант
pop_music = df[(df['total_play_seconds']!=0)&(df['genre_name']=='pop')]
print(pop_music)

#2 вариант
pop_music = df[(df.loc[:, 'total_play_seconds']!=0)&(df.loc[:, 'genre_name']=='pop')]
print(pop_music)

Answer 1

loc is used to fetch an element(s) by condition, you can't put loc in df[] because loc must return a new dataframe(or Series). Use the first option or connect two different locs.
I hope I explained clearly