Most efficient way to melt dataframe with a ton of possible values pandas

问题

I have a long format dataframe like the following:

In reality, my dataframe is about 10k rows and there are about 400 possible values of category. I'd like to melt my dataframe into a wide format like the following:

I can think of a couple ways to do this, but what would be an efficient way to do this transformation?

回答1:

Check with crosstab

 out = pd.crosstab(df['Obs'], df['Category'])

回答2:

Isn't this crosstab:

pd.crosstab(df['Obs'], df['Category'])

来源：https://stackoverflow.com/questions/64419988/most-efficient-way-to-melt-dataframe-with-a-ton-of-possible-values-pandas