np.unique() for unique elements in NumPy - Step-by-Step Execution

Concept Flow - np.unique() for unique elements

Input array

↓

Sort array

↓

Find unique elements

↓

Return unique array

np.unique() takes an array, sorts it, finds unique elements, and returns them as a new array.

Execution Sample

NumPy

import numpy as np
arr = np.array([3, 1, 2, 3, 2, 4])
unique_arr = np.unique(arr)
print(unique_arr)

This code finds unique elements from the array and prints them sorted.

Execution Table

Step	Action	Input/State	Result/Output
1	Input array created	[3, 1, 2, 3, 2, 4]	[3 1 2 3 2 4]
2	Sort array internally	[3 1 2 3 2 4]	[1 2 2 3 3 4]
3	Find unique elements	[1 2 2 3 3 4]	[1 2 3 4]
4	Return unique array	-	[1 2 3 4]

💡 All unique elements extracted and returned as sorted array.

Variable Tracker

Variable	Start	After Step 1	After Step 2	After Step 3	Final
arr	-	[3 1 2 3 2 4]	[3 1 2 3 2 4]	[3 1 2 3 2 4]	[3 1 2 3 2 4]
unique_arr	-	-	-	[1 2 3 4]	[1 2 3 4]

Key Moments - 2 Insights

Why does np.unique() return a sorted array instead of preserving the original order?

np.unique() sorts the array internally to efficiently find unique elements, so the output is always sorted as shown in step 2 and 3 of the execution_table.

Does np.unique() change the original array?

No, np.unique() does not modify the original array 'arr'. It returns a new array with unique elements, as seen in variable_tracker where 'arr' stays the same.

Visual Quiz - 3 Questions

Look at the execution_table, what is the output after step 3?

A [3 1 2 3 2 4]

B [1 2 3 4]

C [1 2 2 3 3 4]

D [4 3 2 1]

💡 Hint

Check the 'Result/Output' column for step 3 in the execution_table.

At which step does np.unique() sort the array internally?

A Step 1

B Step 3

C Step 2

D Step 4

💡 Hint

Look at the 'Action' column in the execution_table for sorting.

If the input array was already sorted, how would the execution_table change?

A Step 2 would show the same sorted array as input

B Step 3 would return duplicates

C Step 4 would return the original array

D Step 1 would be skipped

💡 Hint

Refer to the sorting step and its output in the execution_table.

Concept Snapshot

np.unique(array)
- Returns sorted unique elements from array
- Does not modify original array
- Useful to find distinct values
- Output is always sorted
- Can return indices or counts with options

Full Transcript

np.unique() is a function in numpy that finds unique elements in an array. It first sorts the array internally, then extracts unique values, and returns them as a new sorted array. The original array remains unchanged. This process helps to quickly identify distinct values in data. The output is always sorted, which is important to remember when order matters.