datatable.Frame.cbind()

Append columns of one or more frames to the current Frame.

For example, if the current frame has n columns, and you are appending another frame with k columns, then after this method succeeds, the current frame will have n + k columns. Thus, this method is roughly equivalent to pandas.concat(axis=1).

The frames being cbound must all either have the same number of rows, or some of them may have only a single row. Such single-row frames will be automatically expanded, replicating the value as needed. This makes it easy to create constant columns or to append reduction results (such as min/max/mean/etc) to the current Frame.

If some of the frames have an incompatible number of rows, then the operation will fail with an dt.exceptions.InvalidOperationError. However, if you set the flag force to True, then the error will no longer be raised - instead all frames that are shorter than the others will be padded with NAs.

If the frames being appended have the same column names as the current frame, then those names will be mangled to ensure that the column names in the current frame remain unique. A warning will also be issued in this case.

Parameters

frames
Frame | List[Frame] | None

The list/tuple/sequence/generator expression of Frames to append to the current frame. It may also contain None values, which will be simply skipped.

force
bool

If True, allows Frames to be appended even if they have unequal number of rows. The resulting Frame will have number of rows equal to the largest among all Frames. Those Frames which have less than the largest number of rows, will be padded with NAs (with the exception of Frames having just 1 row, which will be replicated instead of filling with NAs).

return
None

This method alters the current frame in-place, and doesn’t return anything.

except
InvalidOperationError

If trying to cbind frames with the number of rows different from the current frame’s, and the option force is not set.

Notes

Cbinding frames is a very cheap operation: the columns are copied by reference, which means the complexity of the operation depends only on the number of columns, not on the number of rows. Still, if you are planning to cbind a large number of frames, it will be beneficial to collect them in a list first and then call a single cbind() instead of cbinding them one-by-one.

It is possible to cbind frames using the standard DT[i,j] syntax:

df[:, update(**frame1, **frame2, ...)]

Or, if you need to append just a single column:

df["newcol"] = frame1

See also

  • dt.cbind() – function for cbinding frames “out-of-place” instead of in-place;

  • .rbind() – method for row-binding frames.

Examples

DT = dt.Frame(A=[1, 2, 3], B=[4, 7, 0]) frame1 = dt.Frame(N=[-1, -2, -5]) DT.cbind(frame1) DT
ABN
int32int32int32
014-1
127-2
230-5