How can I check whether the numpy array is empty or not?

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How can I check whether the numpy array is empty or not?

I used the following code, but this is fail if the array contains a zero.

if not self.Definition.all():

is this the solution?

if self.Definition == array( [] ):

You can always take a look at the .size attribute. It is defined as an integer, and is zero (0) when there are no elements in the array:

import numpy as np
a = np.array([])

if a.size == 0:
    # Do something when `a` is empty

How can I check whether a numpy array is empty or not?, NumPy Array Object Exercises, Practice and Solution: Write a NumPy program to check whether the numpy array is empty or not. How can I check whether the numpy array is empty or not? I used the following code, but this is fail if the array contains a zero. if not self.Definition.all(): is this the solution? if self.

http://www.scipy.org/Tentative_NumPy_Tutorial#head-6a1bc005bd80e1b19f812e1e64e0d25d50f99fe2

NumPy's main object is the homogeneous multidimensional array. In Numpy dimensions are called axes. The number of axes is rank. Numpy's array class is called ndarray. It is also known by the alias array. The more important attributes of an ndarray object are:

ndarray.ndim the number of axes (dimensions) of the array. In the Python world, the number of dimensions is referred to as rank.

ndarray.shape the dimensions of the array. This is a tuple of integers indicating the size of the array in each dimension. For a matrix with n rows and m columns, shape will be (n,m). The length of the shape tuple is therefore the rank, or number of dimensions, ndim.

ndarray.size the total number of elements of the array. This is equal to the product of the elements of shape.

NumPy: Check whether the numpy array is empty or not, How can I check whether the numpy array is empty or not? I used the following code, but this is fail if the array contains a zero. if not self.Definition.all(): is this the​  NumPy Array Object Exercises, Practice and Solution: Write a NumPy program to check whether the numpy array is empty or not.

One caveat, though. Note that np.array(None).size returns 1! This is because a.size is equivalent to np.prod(a.shape), np.array(None).shape is (), and an empty product is 1.

>>> import numpy as np
>>> np.array(None).size
1
>>> np.array(None).shape
()
>>> np.prod(())
1.0

Therefore, I use the following to test if a numpy array has elements:

>>> def elements(array):
    ...     return array.ndim and array.size

>>> elements(np.array(None))
0
>>> elements(np.array([]))
0
>>> elements(np.zeros((2,3,4)))
24

How can I check whether the numpy array is empty or not?, How can I check whether the numpy array is empty or not? I used the following code, but this is fail if the array contains a zero. if not self. How can I check whether the numpy array is empty or not? I used the following code, but this is fail if the array contains a zero. if not self.Definition.all(): is this the solution?

How can I check whether the numpy array is empty or not , Other methods that work fine for lists or other standard containers fail for numpy arrays. This way fails with numpy arrays because numpy tries to cast the array to​  If we have a numpy array then correct method in all cases, is to use if .size. This size checks the size of the arrays and return True or False accordingly. This size checks the size of the arrays and return True or False accordingly.

Python, numpy.empty(shape, dtype = float, order = 'C') : Return a new array of given shape and Note : empty, unlike zeros, does not set the array values to zero, and may If you like GeeksforGeeks and would like to contribute, you can also write an  An empty array can sometimes cause software crash or unexpected outputs. To avoid this, it is better to check whether an array is empty or not beforehand. There are various methods and functions available in PHP to check whether the defined or given array is an empty or not.

numpy.empty() in Python, https://docs.scipy.org › doc › numpy-1.15.1 › reference › generated › num empty, unlike zeros, does not set the array values to zero, and may therefore be marginally faster. On the other hand, it requires the user to manually set all the values in the array, and should be used with caution.

Comments
  • len(array( [] )) is 0. len(array( [0] ) is 1.
  • do you want to test for a zero-length array, an array containing all zeros, or both? What is your definition of 'empty'?
  • @StevenRumbalski: But len(array([[]]) is 1 too!
  • This is great for numpy, but is unfortunate that it is considered unpythonic for lists. Check out discussion for lists: stackoverflow.com/questions/53513/… It would be nice to use same pattern for numpy arrays and lists.
  • An array containing the None object is not an empty array, see the answers here for further details
  • @DrBwts that's not relevant to this answer.