How to Iterating NumPy Array?

Iterating over a NumPy array means accessing its elements (one by one, or by row/column) using loops or built-in functions.

1. Basic Iteration (1-D Array)

If you have a 1-dimensional NumPy array, you can simply loop through it like a Python list:

import numpy as np

arr = np.array([1, 2, 3, 4, 5])

for x in arr:
    print(x)

Output:

2. Iterating a 2-D Array (Row by Row)

In a 2D array, iteration gives each row as a sub-array:

arr2d = np.array([[1, 2, 3],
                  [4, 5, 6]])

for row in arr2d:
    print(row)

Output:

[1 2 3]
[4 5 6]

3. Iterating Each Element in a Multi-Dimensional Array

If you want to access every element (not just rows), use np.nditer():

arr = np.array([[1, 2, 3],
                [4, 5, 6]])

for x in np.nditer(arr):
    print(x)

Output:

4. Iterating with Data Type Conversion

You can convert elements while iterating, e.g. from int to float:

for x in np.nditer(arr, flags=['buffered'], op_dtypes=['float']):
    print(x)

5. Iterating with Index (Using `np.ndenumerate`)

To access both index and value during iteration:

for idx, x in np.ndenumerate(arr):
    print(idx, x)

Output:

(0, 0) 1
(0, 1) 2
(0, 2) 3
(1, 0) 4
(1, 1) 5
(1, 2) 6

6. Iterating Along Specific Axis

You can iterate over a specific axis (like columns) using np.apply_along_axis:

arr = np.array([[1, 2, 3],
                [4, 5, 6]])

# Iterate column-wise (axis=0)
for col in np.apply_along_axis(lambda x: x, axis=0, arr=arr):
    print(col)

Output:

[1 4]
[2 5]
[3 6]

Summary

Method	Description
`for x in arr:`	Iterates row-by-row (for 2D) or element-by-element (for 1D).
`np.nditer(arr)`	Iterates over each element in any-dimensional array.
`np.ndenumerate(arr)`	Iterates with index and value.
`np.apply_along_axis()`	Iterates along a specific axis (e.g. column-wise).

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How to Iterating NumPy Array?

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1 Answers

1. Basic Iteration (1-D Array)

2. Iterating a 2-D Array (Row by Row)

3. Iterating Each Element in a Multi-Dimensional Array

4. Iterating with Data Type Conversion

5. Iterating with Index (Using np.ndenumerate)

6. Iterating Along Specific Axis

Summary

5. Iterating with Index (Using `np.ndenumerate`)