Loc versus [] in selecting a Series Row

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#1

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My Code: 

age_proportions = wnba['Age'].value_counts(normalize=True).sort_index()*100

proportion_25 = age_proportions[25]/100
percentage_30 = age_proportions[30]
percentage_over_30 = age_proportions[30:].sum()
percentage_below_23 = age_proportions[:23].sum()

What I expected to happen:
I expect to get the summary of percentages for percentage_over_30 and percentage_below_23.

What actually happened:

I get no values

When I look at the solution it’s the same code but using .loc I do not understand why .loc needs to be specified here. The shorthand convention for choosing a slice of a series is Series[x:y]. It is even more confusing because the other lines of code use this exact syntax and are able to get the correct values.

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#2

this will return first 23 rows regardless of whatever index it has.

while this, loc

age_proportions.loc[:23]

will select based on index label. So it will return rows that has index between 0 to 23. And in our case here index is starting from 21 so it will return first three rows 21, 22, and 23.

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#3

Hey Dinshin,

If I understand correct, it is necessary here to specify the index in order for the the right slices of the series to be identified?

#4

Yes, that is right index is necessary here.