Pandas: for loop weirdness

Question

I'm completely baffled by the below snippets. I expected both to give me the same output, but that doesn't seem to be the case.

Answer 1

I think the top snippet is returning the length of the entire dataframe.

Consider :

import pandas as pd
df = pd.DataFrame.from_dict({"A":[1, 1, 0, 0, 1]})
print(len(df["A"]==1))

Output : 5