np.intersect1d() for intersection in NumPy - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does np.intersect1d() do?

It finds the common elements between two arrays and returns them as a sorted array without duplicates.

beginner

How does np.intersect1d() handle duplicates in input arrays?

It removes duplicates and returns only unique common elements in the output.

beginner

Example: What is the output of np.intersect1d([1, 2, 3], [2, 3, 4])?

The output is array([2, 3]) because 2 and 3 are common in both arrays.

intermediate

Can np.intersect1d() be used with arrays of different data types?

Yes, but the arrays should be compatible types so that comparison is possible.

intermediate

What is the difference between np.intersect1d() and Python's set intersection?

np.intersect1d() works on numpy arrays and returns a sorted array without duplicates, while set intersection works on Python sets and returns an unordered set.

What does np.intersect1d() return?

A Common elements sorted without duplicates

B All elements from the first array

C All elements from the second array

D Concatenation of both arrays

np.intersect1d() returns the sorted unique elements common to both arrays.

If a = [1, 2, 2, 3] and b = [2, 2, 4], what is np.intersect1d(a, b)?

A [2, 2]

B [2]

C [1, 2, 3, 4]

D [1, 3, 4]

Duplicates are removed, so only one 2 is returned.

Which of these is true about np.intersect1d()?

A Returns unsorted array

B Returns only elements from first array

C Returns sorted array

D Returns duplicates

The output is always sorted and unique.

Can np.intersect1d() be used with string arrays?

A Only with boolean arrays

B No, only numeric arrays

C Only with integer arrays

D Yes, it works with any comparable data type

It works with any arrays where elements can be compared, including strings.

What happens if there are no common elements between arrays?

A Returns an empty array

B Returns the first array

C Returns the second array

D Raises an error

If no elements match, the result is an empty array.

Explain how np.intersect1d() works and give a simple example.

Think about finding shared items in two lists.

Describe the difference between np.intersect1d() and Python set intersection.

Consider data types and output format.