I know that[:,-1] means in pandas to use every row element and the last column element. But currently I see in the pandas documentation this one [::-1] and I wonder the meaning behind it?

Thanks

CodePudding user response：

In Pandas, the [::-1] syntax is used to reverse the rows of a dataframe. This can be useful when you want to display the data in a different order, or when you want to perform operations on the data in reverse order.

For example, if you have a dataframe df with the following values:

   A  B
0  1  2
1  3  4
2  5  6

You can use the [::-1] syntax to reverse the rows of the dataframe, like this:

df[::-1]

This would return a new dataframe with the rows reversed, like this:

   A  B
2  5  6
1  3  4
0  1  2

You can also use the [::-1] syntax to reverse the rows of a specific column or set of columns in a dataframe. For example, if you want to reverse the rows of the B column, you can do the following:

df['B'][::-1]

This would return a new series with the rows of the B column reversed, like this:

2    6
1    4
0    2
Name: B, dtype: int64

The [::-1] syntax is just one of many ways to manipulate the rows of a dataframe in Pandas. For more information, you can refer to the Pandas documentation.