numpy.insert¶

numpy.insert(arr,obj,values,axis=None)[source]¶

Insert values along the given axis before the given indices.

Parameters:

arr : array_like Input array. obj : int, slice or sequence of ints Object that defines the index or indices before whichvalues isinserted. New in version 1.8.0. Support for multiple insertions whenobj is a single scalar or asequence with one element (similar to calling insert multipletimes). values : array_like Values to insert intoarr. If the type ofvalues is differentfrom that ofarr,values is converted to the type ofarr.values should be shaped so thatarr[...,obj,...]=valuesis legal. axis : int, optional Axis along which to insertvalues. Ifaxis is None thenarris flattened first.

Returns:

out : ndarray A copy ofarr withvalues inserted. Note thatinsertdoes not occur in-place: a new array is returned. Ifaxis is None,out is a flattened array.

See also

append

Append elements at the end of an array.

concatenate

Join a sequence of arrays along an existing axis.

delete

Delete elements from an array.

Notes

Note that for higher dimensional insertsobj=0 behaves very differentfromobj=[0] just likearr[:,0,:] = values is different fromarr[:,[0],:] = values.

Examples

>>>a=np.array([[1,1],[2,2],[3,3]])>>>aarray([[1, 1],       [2, 2],       [3, 3]])>>>np.insert(a,1,5)array([1, 5, 1, 2, 2, 3, 3])>>>np.insert(a,1,5,axis=1)array([[1, 5, 1],       [2, 5, 2],       [3, 5, 3]])

Difference between sequence and scalars:

>>>np.insert(a,[1],[[1],[2],[3]],axis=1)array([[1, 1, 1],       [2, 2, 2],       [3, 3, 3]])>>>np.array_equal(np.insert(a,1,[1,2,3],axis=1),...np.insert(a,[1],[[1],[2],[3]],axis=1))True

>>>b=a.flatten()>>>barray([1, 1, 2, 2, 3, 3])>>>np.insert(b,[2,2],[5,6])array([1, 1, 5, 6, 2, 2, 3, 3])

>>>np.insert(b,slice(2,4),[5,6])array([1, 1, 5, 2, 6, 2, 3, 3])

>>>np.insert(b,[2,2],[7.13,False])# type castingarray([1, 1, 7, 0, 2, 2, 3, 3])

>>>x=np.arange(8).reshape(2,4)>>>idx=(1,3)>>>np.insert(x,idx,999,axis=1)array([[  0, 999,   1,   2, 999,   3],       [  4, 999,   5,   6, 999,   7]])