How to find the intersection between two lists in Python

To find the intersection between two lists in Python, you can convert the lists to sets and then use the set.intersection() method or the & operator. This approach is efficient and takes advantage of the set data structure, which automatically removes duplicates and allows for fast membership tests.

Here's an example using the set.intersection() method:

# The input lists
list1 = [1, 2, 3, 4, 5]
list2 = [3, 4, 5, 6, 7]

# Convert the lists to sets
set1 = set(list1)
set2 = set(list2)

# Find the intersection between the sets
intersection = set1.intersection(set2)

# Convert the intersection back to a list (optional)
intersection_list = list(intersection)

# Print the intersection
print("The intersection between the lists is:", intersection_list)

Output:

The intersection between the lists is: [3, 4, 5]

Here's an example using the & operator:

# The input lists
list1 = [1, 2, 3, 4, 5]
list2 = [3, 4, 5, 6, 7]

# Convert the lists to sets
set1 = set(list1)
set2 = set(list2)

# Find the intersection between the sets
intersection = set1 & set2

# Convert the intersection back to a list (optional)
intersection_list = list(intersection)

# Print the intersection
print("The intersection between the lists is:", intersection_list)

Output:

The intersection between the lists is: [3, 4, 5]

In both examples, we first convert the input lists to sets and then find the intersection between the sets using either the set.intersection() method or the & operator. The result is a set containing the common elements between the two lists. Optionally, you can convert the intersection set back to a list using the list() function.

Python find intersection of two lists:

list1 = [1, 2, 3, 4, 5]
list2 = [3, 4, 5, 6, 7]
intersection = list(set(list1) & set(list2))
print(f"Intersection of lists: {intersection}")

Find common elements between lists with list comprehension:

list1 = [1, 2, 3, 4, 5]
list2 = [3, 4, 5, 6, 7]
intersection = [value for value in list1 if value in list2]
print(f"Intersection of lists: {intersection}")

Intersection of multiple lists in Python:

list1 = [1, 2, 3, 4, 5]
list2 = [3, 4, 5, 6, 7]
list3 = [5, 6, 7, 8, 9]
intersection = list(set(list1) & set(list2) & set(list3))
print(f"Intersection of lists: {intersection}")

Python numpy for finding intersection of arrays:

import numpy as np
array1 = np.array([1, 2, 3, 4, 5])
array2 = np.array([3, 4, 5, 6, 7])
intersection = np.intersect1d(array1, array2)
print(f"Intersection of arrays: {intersection}")

Check if two lists have common elements in Python:

list1 = [1, 2, 3, 4, 5]
list2 = [6, 7, 8, 9, 10]
has_common_elements = any(value in list1 for value in list2)
print(f"Do lists have common elements? {has_common_elements}")

Finding intersection with itertools.filterfalse in Python:

from itertools import filterfalse
list1 = [1, 2, 3, 4, 5]
list2 = [3, 4, 5, 6, 7]
intersection = list(filterfalse(lambda x: x not in list2, list1))
print(f"Intersection of lists: {intersection}")

Using set intersection_update() for common elements in Python:

list1 = [1, 2, 3, 4, 5]
list2 = [3, 4, 5, 6, 7]
set1 = set(list1)
set1.intersection_update(list2)
intersection = list(set1)
print(f"Intersection of lists: {intersection}")

Intersection of lists with reduce() function in Python:

from functools import reduce
list1 = [1, 2, 3, 4, 5]
list2 = [3, 4, 5, 6, 7]
intersection = reduce(set.intersection, [set(list1), set(list2)])
print(f"Intersection of lists: {list(intersection)}")

Find common elements and their count in two lists in Python:

list1 = [1, 2, 3, 4, 5, 5, 5]
list2 = [3, 4, 5, 6, 7, 7, 7]
common_elements = set(list1) & set(list2)
element_count = {element: min(list1.count(element), list2.count(element)) for element in common_elements}
print(f"Common Elements and Their Count: {element_count}")

Intersection of lists using pandas in Python:

import pandas as pd
list1 = [1, 2, 3, 4, 5]
list2 = [3, 4, 5, 6, 7]
intersection_series = pd.Series(list1).isin(list2)
intersection = list(intersection_series[intersection_series].index)
print(f"Intersection of lists: {intersection}")

Using zip() and set for finding common elements in Python:

list1 = [1, 2, 3, 4, 5]
list2 = [3, 4, 5, 6, 7]
intersection = list(set(zip(list1, list2)))
print(f"Intersection of lists: {intersection}")

Python intersection of lists without duplicates:

list1 = [1, 2, 3, 4, 5, 5, 5]
list2 = [3, 4, 5, 6, 7, 7, 7]
intersection = list(set(list1) & set(list2))
print(f"Intersection of lists without duplicates: {intersection}")

Intersection of lists with Counter in Python:

from collections import Counter
list1 = [1, 2, 3, 4, 5]
list2 = [3, 4, 5, 6, 7]
counter1 = Counter(list1)
counter2 = Counter(list2)
intersection = list((counter1 & counter2).elements())
print(f"Intersection of lists: {intersection}")

Finding common elements with loop iteration in Python:

list1 = [1, 2, 3, 4, 5]
list2 = [3, 4, 5, 6, 7]
intersection = [value for value in list1 if value in list2]
print(f"Intersection of lists: {intersection}")