请为我解释以下代码行。 即使用数据框的 2 列创建熊猫系列

Question

industry_usa = f500["industry"][f500["country"] == "USA"].value_counts().head(2)

This is a dataframe where some of its columns are industry and country . So why do we need to locate the 2 columns side by side while creating the indsutry_usa series. Please explain.

Answer 1

I will break it down for you:

f500["industry"] : This selects the series (column) with the same name.

f500["country"] == "USA" : This returns a boolean index containing True for all the rows which have their country column as USA.

f500["industry"][f500["country"] == "USA"] : As you might have guessed, this now is just like any other indexing we do in pandas. So, it selects all those " industry "s where the country is "USA".

.value_counts() : is just to do a count of the unique values. Like we have in Counter class in python

NOTE: The interesting fact is that you could change the order to - f500[f500["country"] == "USA"]["industry"] and still get the same result!!