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

Concept Flow - np.unique() for unique values

Input Array

↓

Sort Array

↓

Identify Unique Values

↓

Return Unique Values Array

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

Execution Sample

NumPy

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

This code finds and prints the unique values from the given array.

Execution Table

Step	Action	Array State	Result
1	Input array created	[3, 1, 2, 3, 2, 4]	Original array
2	Sort array internally	[1, 2, 2, 3, 3, 4]	Sorted array for processing
3	Identify unique values	[1, 2, 3, 4]	Unique values extracted
4	Return unique array	[1, 2, 3, 4]	Output array with unique values

💡 All unique values identified and returned as a sorted array.

Variable Tracker

Variable	Start	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] (unchanged)
unique_vals	N/A	N/A	[1, 2, 3, 4]	[1, 2, 3, 4]

Key Moments - 2 Insights

Why does np.unique() return a sorted array of unique values?

np.unique() sorts the array internally to easily identify unique values in order, as shown in step 2 and 3 of the execution_table.

Does np.unique() change the original array?

No, the original array 'arr' remains unchanged throughout, as shown in variable_tracker where 'arr' keeps its initial values.

Visual Quiz - 3 Questions

Look at the execution_table at step 3, what is the array state?

A [3, 1, 2, 3, 2, 4]

B [1, 2, 2, 3, 3, 4]

C [1, 2, 3, 4]

D [4, 3, 2, 1]

💡 Hint

Check the 'Array State' column at step 3 in the execution_table.

At which step does np.unique() identify unique values?

A Step 1

B Step 3

C Step 2

D Step 4

💡 Hint

Look at the 'Action' column in the execution_table to find when unique values are identified.

If the input array was already sorted, how would step 2 change?

A Step 2 would still sort but no change in array

B Step 2 would be skipped

C Step 2 would reverse the array

D Step 2 would remove duplicates

💡 Hint

np.unique() always sorts internally even if the array is sorted; see step 2 in execution_table.

Concept Snapshot

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

Full Transcript

np.unique() is a function in numpy that finds all unique values in an array. It first sorts the array internally, then identifies unique values by removing duplicates. The original array stays the same. The function returns a new array with unique values sorted in ascending order. This is useful when you want to know which distinct values exist in your data. The execution steps show the input array, sorting, unique identification, and final output. Variables track the original and unique arrays separately to avoid confusion.