datatable.Frame.colindex()

Return the position of the column in the Frame.

The index of the first column is 0, just as with regular python lists.

Parameters

column
str | int | FExpr

If string, then this is the name of the column whose index you want to find.

If integer, then this represents a column’s index. The return value is thus the same as the input argument column, provided that it is in the correct range. If the column argument is negative, then it is interpreted as counting from the end of the frame. In this case the positive value column + ncols is returned.

Lastly, column argument may also be an f-expression such as f.A or f[3]. This case is treated as if the argument was simply "A" or 3. More complicated f-expressions are not allowed and will result in a TypeError.

return
int

The numeric index of the provided column. This will be an integer between 0 and self.ncols - 1.

except
KeyError | IndexError

If the column argument is a string, and the column with such name does not exist in the frame, then a KeyError is raised. When this exception is thrown, the error message may contain suggestions for up to 3 similarly looking column names that actually exist in the Frame.

If the column argument is an integer that is either greater than or equal to ncols or less than -ncols, then an IndexError is raised.

Examples

df = dt.Frame(A=[3, 14, 15], B=["enas", "duo", "treis"],
              C=[0, 0, 0])
df.colindex("B")

1

df.colindex(-1)

2

from datatable import f
df.colindex(f.A)

0