Get numpy 2D array from user input

Question

I am trying to get a numpy two-dimensional array from user input except it does not work properly as input() returns a 'str' type while the numpy array() method expects a tuple:

import numpy as N

def main():
    A = input()       # the user is expected to enter a 2D array like [[1,2],[3,4]] for example
    A = N.array(A)    # since A is a 'str' A
    print(A.shape)    # output is '()' instead of '(2, 2)' showing the previous instruction didn't work as expected

if __name__ == "__main__":
main()

So my question would be: How can I turn the input string into a tuple so that the array() method properly turns the input into a numpy 2D array?

Thanks in advance.

You will have to manually iterate through the string and get the numbers out in tuple form to create the array. — Vivek Rai
– Vivek Rai, Commented Oct 6, 2014 at 15:33

Brett Lempereur · Accepted Answer · 2014-10-06 15:31:41Z

2

The following interactive session worked fine in my case:

>>> A = input()
[[1, 2], [3, 4]]
>>> 
>>> A
[[1, 2], [3, 4]]
>>> type(A)
<type 'list'>
>>> import numpy
>>> numpy.array(A)
array([[1, 2],
      [3, 4]])
>>>

Are you entering the data wrapped in quotes, i.e.:

>>> A = input()
"[[1, 2], [3, 4]]"
>>> A
'[[1, 2], [3, 4]]'
>>> type(A)
<type 'str'>

As that's the only reason I can think of for your code to fail. Input does not return a string unless the user types one in; it is equivalent to eval(raw_input()) in your case.

answered Oct 6, 2014 at 15:31

Brett Lempereur

8155 silver badges11 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

DSM Over a year ago

"Input does not return a string unless the user types one in": not true in Python 3.

Brett Lempereur Over a year ago

Thanks for letting me know, it's a long time since I've used anything input() related.

Sidharth Shah · Accepted Answer · 2014-10-06 15:34:48Z

2

I think the code is correct you need to change the way you input data. Please look at following code snippet

>>> import numpy as N
>>> A = input()
((1,2),(3,4))
>>> type(A[0][0])
<type 'int'>

answered Oct 6, 2014 at 15:34

Sidharth Shah

1,6071 gold badge12 silver badges14 bronze badges

Comments

Kevin Bill · Accepted Answer · 2018-05-13 11:25:24Z

2

Brett Lempereur and Sidharth Shah's answers is just for Python2 because input() in Python3 will return str by default.

In Python3, you would also need to use ast to eval string input to list.

>>> import ast
>>> import numpy as np
>>> matrixStr = input()
[[1, 2], [3, 4]]
>>> type(matrixStr)
str
>>> matrixList = ast.literal_eval(matrixStr)
>>> type(matrixList)
list
>>> matrix = np.array(matrix)

answered May 13, 2018 at 11:25

Kevin Bill

313 bronze badges

Comments

Nik_Coding · Accepted Answer · 2019-12-24 15:17:40Z

0

Or simply you can just do this:

import numpy

def array_input():
    a = eval(input('Enter list: '))
    b = numpy.array(a)
return b
print(array_input())

answered Dec 24, 2019 at 15:17

Nik_Coding

1

Comments

cwancu · Accepted Answer · 2020-03-16 08:25:40Z

0

import numpy as np
arr = np.array([[int(x) for x in input(f"Enter the value{[i]}:").split()] for i in range(3)])

print(arr)

answered Mar 16, 2020 at 8:25

cwancu

13 bronze badges

Comments

cwancu · Accepted Answer · 2024-03-28 10:03:46Z

0

Numpy 2D array user defined input

# Importing the NumPy library for numerical computations
import numpy as np

lis = []  # Initializing an empty list to store user input values

# Looping three times to get input for three different values
for i in range(3):
    # Prompting the user to enter a value and splitting it into separate values
    # based on the current iteration index i
    user_input = input(f"Enter the value {[i]}:").split()

    # Appending the entered values to the list
    lis.append(user_input)

    # Converting the list of entered values to a NumPy array with integer data type
    arr = np.array(lis, dtype=int)

print(arr)  # Printing the final NumPy array containing the entered values

edited Mar 28, 2024 at 10:03

answered Mar 16, 2020 at 8:46

cwancu

13 bronze badges

1 Comment

mw509 Over a year ago

It may be a great answer but without an explanation of how you arrived at it, it may just turn out to not be useful to others

parvus · Accepted Answer · 2018-02-22 05:20:16Z

-1

to get an integer input you have to pass input() within int() like...

A=int(input())
type(A)
>>>int

edited Feb 22, 2018 at 5:20

parvus

6,0566 gold badges42 silver badges66 bronze badges

answered Feb 22, 2018 at 3:26

Md Shahid

1

Collectives™ on Stack Overflow

Get numpy 2D array from user input

7 Answers 7

2 Comments

Comments

Comments

Comments

Comments

1 Comment

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

7 Answers 7

2 Comments

Comments

Comments

Comments

Comments

1 Comment

Comments

Your Answer

Sign up or log in

Post as a guest

Related