Expand the shape of an array. Insert a new axis that will appear at the `axis` position in the expanded array shape. Parameters ---------- a : array_like Input array. axis : int or tuple of ints Position in the expanded axes where the new axis (or axes)
(a, axis)
| 511 | |
| 512 | @array_function_dispatch(_expand_dims_dispatcher) |
| 513 | def expand_dims(a, axis): |
| 514 | """ |
| 515 | Expand the shape of an array. |
| 516 | |
| 517 | Insert a new axis that will appear at the `axis` position in the expanded |
| 518 | array shape. |
| 519 | |
| 520 | Parameters |
| 521 | ---------- |
| 522 | a : array_like |
| 523 | Input array. |
| 524 | axis : int or tuple of ints |
| 525 | Position in the expanded axes where the new axis (or axes) is placed. |
| 526 | |
| 527 | .. deprecated:: 1.13.0 |
| 528 | Passing an axis where ``axis > a.ndim`` will be treated as |
| 529 | ``axis == a.ndim``, and passing ``axis < -a.ndim - 1`` will |
| 530 | be treated as ``axis == 0``. This behavior is deprecated. |
| 531 | |
| 532 | .. versionchanged:: 1.18.0 |
| 533 | A tuple of axes is now supported. Out of range axes as |
| 534 | described above are now forbidden and raise an `AxisError`. |
| 535 | |
| 536 | Returns |
| 537 | ------- |
| 538 | result : ndarray |
| 539 | View of `a` with the number of dimensions increased. |
| 540 | |
| 541 | See Also |
| 542 | -------- |
| 543 | squeeze : The inverse operation, removing singleton dimensions |
| 544 | reshape : Insert, remove, and combine dimensions, and resize existing ones |
| 545 | doc.indexing, atleast_1d, atleast_2d, atleast_3d |
| 546 | |
| 547 | Examples |
| 548 | -------- |
| 549 | >>> x = np.array([1, 2]) |
| 550 | >>> x.shape |
| 551 | (2,) |
| 552 | |
| 553 | The following is equivalent to ``x[np.newaxis, :]`` or ``x[np.newaxis]``: |
| 554 | |
| 555 | >>> y = np.expand_dims(x, axis=0) |
| 556 | >>> y |
| 557 | array([[1, 2]]) |
| 558 | >>> y.shape |
| 559 | (1, 2) |
| 560 | |
| 561 | The following is equivalent to ``x[:, np.newaxis]``: |
| 562 | |
| 563 | >>> y = np.expand_dims(x, axis=1) |
| 564 | >>> y |
| 565 | array([[1], |
| 566 | [2]]) |
| 567 | >>> y.shape |
| 568 | (2, 1) |
| 569 | |
| 570 | ``axis`` may also be a tuple: |