NumPy - Array Attributes

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In this chapter, we will discuss the various array attributes of NumPy.

ndarray.shape

This array attribute returns a tuple consisting of array dimensions. It can also be used to resize the array.

Example 1

import numpy as np 
a = np.array([[1,2,3],[4,5,6]]) 
print a.shape

The output is as follows −

(2, 3)

Example 2

# this resizes the ndarray 
import numpy as np 

a = np.array([[1,2,3],[4,5,6]]) 
a.shape = (3,2) 
print a 

The output is as follows −

[[1, 2] 
 [3, 4] 
 [5, 6]]

Example 3

NumPy also provides a reshape function to resize an array.

import numpy as np 
a = np.array([[1,2,3],[4,5,6]]) 
b = a.reshape(3,2) 
print b

The output is as follows −

[[1, 2] 
 [3, 4] 
 [5, 6]]

ndarray.ndim

This array attribute returns the number of array dimensions.

Example 1

# an array of evenly spaced numbers 
import numpy as np 
a = np.arange(24) 
print a

The output is as follows −

[0 1  2  3  4  5  6  7  8  9  10  11  12  13  14  15  16 17 18 19 20 21 22 23] 

Example 2

# this is one dimensional array 
import numpy as np 
a = np.arange(24) 
a.ndim  

# now reshape it 
b = a.reshape(2,4,3) 
print b 
# b is having three dimensions

The output is as follows −

[[[ 0,  1,  2] 
  [ 3,  4,  5] 
  [ 6,  7,  8] 
  [ 9, 10, 11]]  
  [[12, 13, 14] 
   [15, 16, 17]
   [18, 19, 20] 
   [21, 22, 23]]] 

numpy.itemsize

This array attribute returns the length of each element of array in bytes.

Example 1

# dtype of array is int8 (1 byte) 
import numpy as np 
x = np.array([1,2,3,4,5], dtype = np.int8) 
print x.itemsize

The output is as follows −

1

Example 2

# dtype of array is now float32 (4 bytes) 
import numpy as np 
x = np.array([1,2,3,4,5], dtype = np.float32) 
print x.itemsize

The output is as follows −

4

numpy.flags

The ndarray object has the following attributes. Its current values are returned by this function.

Example

The following example shows the current values of flags.

import numpy as np 
x = np.array([1,2,3,4,5]) 
print x.flags

The output is as follows −

C_CONTIGUOUS : True 
F_CONTIGUOUS : True 
OWNDATA : True 
WRITEABLE : True 
ALIGNED : True 
UPDATEIFCOPY : False