python 2d array

+2 votes
How to define a 2-D array without an initialized length, something like this: A = [][]
Apr 15, 2018 in Python by ana1504.k
• 6,630 points
81 views

4 answers to this question.

Your answer

Your name to display (optional):
Privacy: Your email address will only be used for sending these notifications.
+2 votes

You can use NumPy library of Python, below I have mentioned few ways to create 2-D arrays using NumPy:
>>> import numpy
>>> numpy.zeros((5, 5))
array([[ 0., 0., 0., 0., 0.],
[ 0., 0., 0., 0., 0.],
[ 0., 0., 0., 0., 0.],
[ 0., 0., 0., 0., 0.],
[ 0., 0., 0., 0., 0.]])
numpy provides a matrix type as well. It's less commonly used, and some people recommend against using it. But it's useful for people coming to numpy from Matlab, and in some other contexts. I thought I'd include it since we're talking about matrices!

>>> numpy.matrix([[1, 2], [3, 4]])
matrix([[1, 2],
[3, 4]])
Here are some other ways to create 2-d arrays and matrices (with output removed for compactness):

numpy.matrix('1 2; 3 4') # use Matlab-style syntax
numpy.arange(25).reshape((5, 5)) # create a 1-d range and reshape
numpy.array(range(25)).reshape((5, 5)) # pass a Python range and reshape
numpy.array([5] * 25).reshape((5, 5)) # pass a Python list and reshape
numpy.empty((5, 5)) # allocate, but don't initialize
numpy.ones((5, 5)) # initialize with ones
numpy.ndarray((5, 5)) # use the low-level constructor

answered Apr 15, 2018 by anto.trigg4
• 3,420 points
+2 votes
>>> import numpy
>>> numpy.zeros((5, 5))
array([[ 0.,  0.,  0.,  0.,  0.],
       [ 0.,  0.,  0.,  0.,  0.],
       [ 0.,  0.,  0.,  0.,  0.],
       [ 0.,  0.,  0.,  0.,  0.],
       [ 0.,  0.,  0.,  0.,  0.]])
answered Oct 18, 2018 by rishav
+2 votes
>>> matrix = 5*[5*[0]]
>>> matrix
[[0, 0, 0, 0, 0], [0, 0, 0, 0, 0], [0, 0, 0, 0, 0], [0, 0, 0, 0, 0], [0, 0, 0, 0, 0]]
>>> matrix[4][4] = 2
>>> matrix
[[0, 0, 0, 0, 2], [0, 0, 0, 0, 2], [0, 0, 0, 0, 2], [0, 0, 0, 0, 2], [0, 0, 0, 0, 2]]
answered Oct 18, 2018 by pinre
+2 votes

You should make a list of lists, and the best way is to use nested comprehensions:

>>> matrix = [[0 for i in range(5)] for j in range(5)]
>>> pprint.pprint(matrix)
[[0, 0, 0, 0, 0],
 [0, 0, 0, 0, 0],
 [0, 0, 0, 0, 0],
 [0, 0, 0, 0, 0],
 [0, 0, 0, 0, 0]]
answered Oct 18, 2018 by ritu

Related Questions In Python

0 votes
1 answer

How do I trim extra zeros from a 2D array in python?

Hey @Laksha, you can try something like ...READ MORE

answered May 29 in Python by Yamini
14 views
+2 votes
11 answers

How to print array/ list without brackets in python?

name=["a","b","c"] print (', '.join(name)) It will simply take all ...READ MORE

answered Apr 18, 2018 in Python by aayushi
• 750 points
13,971 views
0 votes
1 answer
+3 votes
2 answers

how to print array integer without [] bracket in python like result = 1,2,3,4,5

Hey @abhijmr.143, you can print array integers ...READ MORE

answered Aug 4, 2018 in Python by Omkar
• 66,880 points

edited Aug 8, 2018 by Omkar 328 views
0 votes
1 answer

how can i count the items in a list?

suppose you have a list a = [0,1,2,3,4,5,6,7,8,9,10] now ...READ MORE

answered May 2 in Python by Mohammad
• 1,400 points
54 views
+4 votes
7 answers
+2 votes
2 answers

How can I create a new file in Python?

You can try the below code which ...READ MORE

answered Mar 31, 2018 in Python by anto.trigg4
• 3,420 points
49 views

© 2018 Brain4ce Education Solutions Pvt. Ltd. All rights Reserved.
"PMP®","PMI®", "PMI-ACP®" and "PMBOK®" are registered marks of the Project Management Institute, Inc. MongoDB®, Mongo and the leaf logo are the registered trademarks of MongoDB, Inc.