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

Recall & Review

beginner

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

np.unique() finds all the unique elements in an array and returns them sorted.

intermediate

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

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

intermediate

What does np.unique(array, return_counts=True) return?

It returns two arrays: one with unique elements and one with the count of each unique element in the original array.

beginner

True or False: np.unique() always returns the unique elements in sorted order.

True. The unique elements returned by np.unique() are sorted by default.

beginner

How can np.unique() help in real-life data cleaning?

It helps find all distinct values in data, like unique customer IDs or unique product names, which is useful to remove duplicates or analyze categories.

What does np.unique() return by default?

A Only the first element

B All elements including duplicates

C All unique elements sorted

D Random elements

np.unique() returns all unique elements sorted by default.

Which parameter returns the count of each unique element in np.unique()?

A return_counts

B return_index

C return_inverse

D return_sorted

return_counts=True returns the count of each unique element.

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

A return_inverse

B return_index

C return_positions

D return_counts

return_index=True gives indices of the first occurrence of unique elements.

Does np.unique() modify the original array?

A No, it returns the original array unchanged

B Yes, it sorts the original array

C Yes, it removes duplicates in place

D No, it returns a new array

np.unique() returns a new array with unique elements; it does not change the original array.

What type of data is np.unique() most useful for?

A Finding duplicates in data

B Sorting numbers only

C Calculating averages

D Creating random arrays

np.unique() helps find unique values, which is useful to identify duplicates.

Explain how you would use np.unique() to find unique values and their counts in a dataset.

Think about the parameters that give you extra information besides unique values.

Describe a real-world example where finding unique elements with np.unique() is helpful.

Consider situations like customer lists or product inventories.