The vstack() method stacks the given sequence of input arrays vertically.
Example
import numpy as np
array1 = np.array([[0, 1], [2, 3]])
array2 = np.array([[4, 5], [6, 7]])
# stack the arrays
stackedArray = np.vstack((array1, array2))
print(stackedArray)
'''
Output
[[0 1]
[2 3]
[4 5]
[6 7]]
'''
vstack() Syntax
The syntax of vstack() is:
numpy.vstack(tup)
vstack() Arguments
The vstack() method takes a single argument:
tup- a tuple of arrays to be stacked
Note: The shape of all arrays in a given tuple must be the same, except the first dimension because we are stacking in axis 0.
vstack() Return Value
The vstack() method returns the vertically stacked array.
Example 1: Vertically Stack Arrays
import numpy as np
array1 = np.array([[0, 1], [2, 3]])
array2 = np.array([[4, 5], [6, 7]])
array3 = np.array([[8, 9]])
# stack the arrays
stackedArray = np.vstack((array1, array2, array3))
print(stackedArray)
Output
[[0 1] [2 3] [4 5] [6 7] [8 9]]
Example 2: Vertically Stack Arrays of Invalid Shapes
import numpy as np
array1 = np.array([[0, 1], [2, 3]])
array2 = np.array([[4, 5, 6], [7, 8, 9]])
# stacks the arrays
stackedArray = np.vstack((array1, array2))
print(stackedArray)
Output
ValueError: all the input array dimensions except for the concatenation axis must match exactly, but along dimension 1, the array at index 0 has size 2 and the array at index 1 has size 3