NumPy - reshape() function

The NumPy reshape() function is used to give a new shape to an array without changing its data. The syntax for using this function is given below:

Syntax

numpy.reshape(a, newshape, order='C')

Parameters

`a`	`Required.` Specify the array to be reshaped.
`newshape`	`Required.` Specify int or tuple of ints. The new shape should be compatible with the original shape. If an integer, then the result will be a 1-D array of that length. One shape dimension can be -1. In this case, the value is inferred from the length of the array and remaining dimensions.
`order`	`Optional.` Specify order. Read the elements of the array using this index order, and place the elements into the reshaped array using this index order. 'C' - read / write the elements using C-like index order, with the last axis index changing fastest, back to the first axis index changing slowest. 'F' - read / write the elements using Fortran-like index order, with the first index changing fastest, and the last index changing slowest. 'A' - read / write the elements in Fortran-like index order if a is Fortran contiguous in memory, C-like order otherwise. Note: 'C' and 'F' options take no account of the memory layout of the underlying array, and only refer to the order of indexing.

Return Value

Returns ndarray. This will be a new view object if possible; otherwise, it will be a copy. Note there is no guarantee of the memory layout (C- or Fortran- contiguous) of the returned array.

Example: reshape() an array

In the example below, the reshape() function is used to reshape an array using default parameters.

import numpy as np
arr = np.array([[1,2,3],[4,5,6]])
print("Original Array:")
print(arr)

#reshaping array from (2,3) -> (3,2)
print("\nReshaped Array:")
print(np.reshape(arr, (3,2)))

#flatten the array
print("\nFlattened Array:")
print(np.reshape(arr, -1))

The output of the above code will be:

Original Array:
[[1 2 3]
 [4 5 6]]

Reshaped Array:
[[1 2]
 [3 4]
 [5 6]]

Flattened Array:
[1 2 3 4 5 6]

Example: reshape() with C-like index ordering

By default reshape function uses C-like ordering. A C-like ordering is equivalent to first raveling the array then inserting the elements into the new array using C-like index order. Consider the example below.

import numpy as np
arr = np.array([[1,2,3],[4,5,6]])
print("Original Array:")
print(arr)

#reshaping array from (2,3) -> (3,2)
print("\nReshaped Array:")
print(np.reshape(arr, (3,2), order='C'))

#raveling the initial array
ravelarr = np.ravel(arr, order='C')
print("\nRaveled Array:")
print(ravelarr)

#reshaping the ravel array
print("\nReshaped Array from raveled array:")
print(np.reshape(ravelarr, (3,2), order='C'))

The output of the above code will be:

Original Array:
[[1 2 3]
 [4 5 6]]

Reshaped Array:
[[1 2]
 [3 4]
 [5 6]]

Raveled Array:
[1 2 3 4 5 6]

Reshaped Array from raveled array:
[[1 2]
 [3 4]
 [5 6]]

Example: reshape() with F-like index ordering

A F-like ordering is equivalent to first raveling the array then inserting the elements into the new array using F-like index order. Consider the example below.

import numpy as np
arr = np.array([[1,2,3],[4,5,6]])
print("Original Array:")
print(arr)

#reshaping array from (2,3) -> (3,2)
print("\nReshaped Array:")
print(np.reshape(arr, (3,2), order='F'))

#raveling the initial array
ravelarr = np.ravel(arr, order='F')
print("\nRaveled Array:")
print(ravelarr)

#reshaping the ravel array
print("\nReshaped Array from raveled array:")
print(np.reshape(ravelarr, (3,2), order='F'))

The output of the above code will be:

Original Array:
[[1 2 3]
 [4 5 6]]

Reshaped Array:
[[1 5]
 [4 3]
 [2 6]]

Raveled Array:
[1 4 2 5 3 6]

Reshaped Array from raveled array:
[[1 5]
 [4 3]
 [2 6]]

❮ NumPy - Array Manipulation