Initializing numpy array of zeros using for loop

Question

I require to create a list of numpy arrays with zeros to accomplish something as follows.

import numpy as np
a = np.zeros([10,1])
b = np.zeros([10,1])
c = np.zeros([10,1])
d = np.zeros([10,1])
e = np.zeros([10,1])

Therefore, I created a list of variable names and ran a for loop as follows

list = ['a', 'b' , 'c', 'd' , 'e']
for i in list:
    i = np.zeros([10,1])

I know I am wrong or missing something while doing the above steps. Can someone tell me what's the mistake and a proper way to do it?

You are assigning array to a string instead of variable.

Space Impact
– Space Impact

2018-09-18 12:06:43 +00:00
Commented Sep 18, 2018 at 12:06 — Space Impact
– Space Impact, Commented Sep 18, 2018 at 12:06

jkhadka · Accepted Answer · 2018-09-18 12:07:12Z

Best way is to use dictionary:

list = ['a', 'b' , 'c', 'd' , 'e']
mydict = {}
for i in list:
    mydict[i] = np.zeros([10,1])



>>>mydict['a']
array([[ 0.],
       [ 0.],
       [ 0.],
       [ 0.],
       [ 0.],
       [ 0.],
       [ 0.],
       [ 0.],
       [ 0.],
       [ 0.]])

With your previous statement : i = np.zeros([10,1]) , you were just reassigning value of i to the numpy array and not actually assigning the array to the "variable", like below :

list = ['a', 'b' , 'c', 'd' , 'e']
mydict = {}
for i in list:
    i= np.zeros([10,1])
print i 


[[ 0.]
 [ 0.]
 [ 0.]
 [ 0.]
 [ 0.]
 [ 0.]
 [ 0.]
 [ 0.]
 [ 0.]
 [ 0.]]

Guimoute · Accepted Answer · 2018-09-18 12:09:28Z

1

Would you be fine with using a dictionnary?

Dict = {}

list = ['a', 'b' , 'c', 'd' , 'e']
    for i in list:
       Dict[i] = np.zeros([10,1])

The various i are you dictionnary keys now, so after the for loop you can retrieve the desired array using a = Dict["a"]. I'm sure there is a more elegant solution though.

answered Sep 18, 2018 at 12:09

Guimoute

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Comments

Ahmed Yousif · Accepted Answer · 2018-09-18 12:55:05Z

0

you can use following code that init it in inline dictionary

  mydict = { i:np.zeros([10,1]) for i in ['a', 'b' , 'c', 'd' , 'e']  }

    print(mydict['a'])

edited Sep 18, 2018 at 12:55

answered Sep 18, 2018 at 12:12

Ahmed Yousif

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