CODEWITHSUNDEEP
pythonarraysnumpymultidimensional-array
user6210457
user6210457

Reputation: 409

How to Search a Number in a Numpy Array in Python

in my program I want to have 1D array, convert it to a 2D array, convert it back to a 1D array again and I want to search for a value in the final array. In order to change 1D array to 2D, I used numpy. I used where() function in order to search through the array and in the end I get this output:

(array([4], dtype=int32),)

I get this result but I only need its index, 4 in case. Is there a way which I can only get the numerical result of the where() function or is there an alternative way which allows me to do 1D to 2D and 2D to 1D conversions without using numpy?

import numpy as np

a = [1,2,3,4,5,6,7,8,9];
print(a)
b = np.reshape(a,(3,3))
print(b)
c = b.ravel()
print(c)
d = np.where(c==5)
print(d)

Upvotes: 0

Views: 1089

Answers (4)

Paul Panzer
Paul Panzer

Reputation: 53029

No numpy version:

from itertools import chain

a = list(range(1, 10))
b = list(zip(*3*(iter(a),)))
c = list(chain.from_iterable(b))
d = c.index(5)

Upvotes: 2

wwii
wwii

Reputation: 23753

...is there an alternative way which allows me to do 1D to 2D and 2D to 1D conversions without using numpy?:

1-d to 2-d

b = [1,2,3,4,5,6,7,8,9]
ncols = 3
new = []
for i,n in enumerate(b):
    if i % ncols == 0:
        z = []
        new.append(z)
    z.append(n)

2-d to 1-d: How to make a flat list out of list of lists?

Upvotes: 2

Kingsmanvk
Kingsmanvk

Reputation: 39

import numpy as np

a = [1,2,3,4,5,6,7,8,9];
print(a)
b = np.reshape(a,(3,3))
print(b)
c = b.ravel()
print(c)
d = np.where(c==5)
print(d[0][0])

Upvotes: 1

MadLordDev
MadLordDev

Reputation: 260

In your case 

print(d[0][0])

will give you the index as integer. But if you want to use any other methods I recommend checking Is there a NumPy function to return the first index of something in an array?

Upvotes: 1

Related Questions