np.unique() for unique values in NumPy - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the function np.unique() do in NumPy?

np.unique() finds all the unique values in a NumPy array and returns them sorted.

intermediate

How can you get the indices of the unique values in the original array using np.unique()?

Use the argument return_index=True. It returns the indices of the first occurrences of the unique values.

intermediate

What does the return_counts=True option do in np.unique()?

It returns how many times each unique value appears in the original array.

intermediate

If you want to find unique rows in a 2D NumPy array, can np.unique() help?

Yes, by using axis=0, np.unique() returns unique rows.

beginner

What is the order of the unique values returned by np.unique()?

The unique values are always returned sorted in ascending order.

What does np.unique() return by default?

A Original array with duplicates removed but order kept

B Indices of duplicates

C Sorted unique values from the array

D Sum of unique values

By default, np.unique() returns the sorted unique values from the input array.

How do you get the count of each unique value using np.unique()?

A Set <code>return_counts=True</code>

B Set <code>return_index=True</code>

C Use <code>np.count()</code>

D Use <code>np.sum()</code>

The return_counts=True option returns the count of each unique value.

Which argument helps find unique rows in a 2D array?

A <code>sorted=False</code>

B <code>axis=1</code>

C <code>return_index=True</code>

D <code>axis=0</code>

Using axis=0 tells np.unique() to find unique rows.

What type of object does np.unique() return?

A A Python list of unique values

B A sorted NumPy array of unique values

C A dictionary with counts

D A scalar value

np.unique() returns a sorted NumPy array of unique values.

If you want the indices of unique values in the original array, which parameter do you use?

A <code>return_index=True</code>

B <code>return_inverse=True</code>

C <code>return_counts=True</code>

D <code>axis=1</code>

return_index=True returns the indices of the first occurrences of unique values.

Explain how to use np.unique() to find unique values and their counts in a NumPy array.

Think about the arguments that give extra information besides unique values.

Describe how to find unique rows in a 2D NumPy array using np.unique().

Consider the axis argument for row-wise uniqueness.