Not the most efficient one, but by far the most obvious way to do it is:
>>> a = [1, 2, 3, 4, 5]
>>> b = [9, 8, 7, 6, 5]
>>> set(a) & set(b)
{5}
if order is significant you can do it with list comprehensions like this:
>>> [i for i, j in zip(a, b) if i == j]
[5]
(only works for equal-sized lists, which order-significance implies).
Answer from SilentGhost on Stack Overflow Top answer 1 of 16
700
Not the most efficient one, but by far the most obvious way to do it is:
>>> a = [1, 2, 3, 4, 5]
>>> b = [9, 8, 7, 6, 5]
>>> set(a) & set(b)
{5}
if order is significant you can do it with list comprehensions like this:
>>> [i for i, j in zip(a, b) if i == j]
[5]
(only works for equal-sized lists, which order-significance implies).
2 of 16
567
Use set.intersection(), it's fast and readable.
>>> set(a).intersection(b)
set([5])
DigitalOcean
digitalocean.com › community › tutorials › how-to-compare-two-lists-in-python
How to Compare Two Lists in Python | DigitalOcean
July 22, 2025 - When your goal is to find which elements are shared or which are unique between two lists, the most efficient and Pythonic approach is to use the set() function. It creates set objects using the given lists and then compares the sets for equality using the == operator.
How can I compare two lists in python and return not matches - Stack Overflow
And if you don't care that the result should be a list you could just skip the final casting. ... This will discard duplicates in a or b that are not matched by the other. 2016-03-01T01:36:14.933Z+00:00 ... It will, but comparing matches with duplicates makes little sense. 2016-03-01T01:36:58.66Z+00:00 ... Unless it has sense... I don't think you can assert that it doesn't have a purpose without knowing the application. 2016-03-01T01:37:52.173Z+00:00 ... "I would like to return ... More on stackoverflow.com
python: compare two lists and return matches in order - Stack Overflow
I have two lists of unequal length and I would like to compare and pull matched values in the order from the first list, so a in this example. a = ['a','s','d','f'] b = ['e','d','y','a','t','v'] More on stackoverflow.com
how to best compare two lists using a for loop?
You're comparing the entry in a (call it x) with the entry at the xth position in b. If you want to go through things stepwise like this, consider using the enumerate function to keep indices consistent. newlist = [] for i, value in enumerate(a): if a[i] == b[i]: newlist.append(i) print(newlist) Here's how that looks as a list comprehension: print([i for i, val in enumerate(a) if a[i] == b[i]]) More on reddit.com
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August 17, 2022How can I compare two lists and return the positions(?) of not matches
You could do a if statement in a for loop Ex : for I in range (5): If l1[i] != l2[i] : print(i) It would output 1 and 4 since index starts at 0 If for some whatever reason you want 2 and 5 you can do print(I + 1) instead More on reddit.com
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December 19, 202405:26
How can I compare two lists in python and return matches - YouTube
23:39
How to Compare Lists in Python Made Easy! - YouTube
01:20
How to Compare Two Lists and Get Common Elements in Python | NareshIT ...
08:56
Python Tips and Tricks: 4 Ways to Compare Lists - YouTube
PYTHON : How can I compare two lists in python and return ...
Compare Two Lists and Find Matches & Differences with 1 ...
Statistics Globe
statisticsglobe.com › home › python programming language for statistics & data science › compare two lists & return matches & differences in python (2 examples)
How to Compare Two Python Lists & Return Matches & Differences
July 7, 2023 - Here’s an example: # Finding matches between lists matches = [element for element in list1 if element in list2] print(matches) # [4, 5] In this example, we use a list comprehension to iterate over the elements of list1 and check if each element ...
Squash
squash.io › how-to-compare-two-lists-in-python-and-return-matches
How to Compare Two Lists in Python and Return Matches
November 2, 2023 - One way to compare two lists in Python and return the matches is by using list comprehension.
Top answer 1 of 6
61
One of the simplest and quickest is:
new_list = list(set(list1).difference(list2))
BONUS! If you want an intersection (return the matches):
new_list = list(set(list1).intersection(list2))
2 of 6
34
Just use a list comprehension:
def returnNotMatches(a, b):
return [[x for x in a if x not in b], [x for x in b if x not in a]]
Miguendes
miguendes.me › python-compare-lists
The Best Ways to Compare Two Lists in Python
July 2, 2022 - Learn to compare if two lists are equal, find elements that match, get the difference between 2 lists, compare lists of dictionaries, and list of strings.
W3docs
w3docs.com › python
How can I compare two lists in python and return matches
Note that the intersection() method returns a set, so we are converting it to a list to be able to print it. Also you can use & operator for intersection · list1 = [1, 2, 3, 4, 5] list2 = [4, 5, 6, 7, 8] matches = list(set(list1) & set(list2)) ...
The Web Dev
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How to compare two lists and return matches with Python? - The Web Dev
November 20, 2021 - To compare two lists and return matches with Python, we can use the set’s intersection method.
Python Guides
pythonguides.com › how-to-compare-two-lists-in-python-and-return-non-matches-elements
Compare Two Lists in Python and Get Non-Matching Elements
September 8, 2025 - Learn how to compare two lists in Python and return non-matching elements using simple methods like loops, sets, and list comprehensions with clear examples.
CSEstack
csestack.org › home › [6 ways] compare two lists in python and return non-match elements
[6 Ways] Compare Two Lists in Python and Return Non-Match Elements
July 25, 2021 - How to compare two lists in Python? Using lambda function, sort(), set() method to check if two lists are equal and have same elements.
TutorialsPoint
tutorialspoint.com › how-to-compare-two-lists-in-python
How to compare two lists in Python?
import collections def ... Same frequency: Equal Different frequency: Not equal · This method compares elements at corresponding positions and counts matches....
Note.nkmk.me
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Compare Lists in Python | note.nkmk.me
May 10, 2023 - Converting a list to a set (set) allows set operations. To check if two lists partially match, i.e., if they have at least one common element, use the isdisjoint() method of set. It accepts not only sets but also other iterable objects, such ...
pythontutorials
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How to Compare Two Lists in Python and Return Matches (with Examples) — pythontutorials.net
A for loop is the most intuitive way to compare two lists, especially for beginners. It involves iterating over one list and checking if each element exists in the second list. list1 = [1, 2, 3, 4, 5, 3] # Contains duplicate "3" list2 = [4, ...
STechies
stechies.com › compare-lists-python-using-set-cmp-function
How to Compare Two Lists in Python using set(), cmp() and difference() Functions
# Custom python code to check if list one is equal to list two by taking difference # Define function name difference def difference (list1, list2): list_dif = [i for i in list1 + list2 if i not in list1 or i not in list2] return list_dif # Initializing list 1 and list 2 x = [10, 15, 20, 25, 30, 35, 40] y = [25, 40, 35] print ("List first: " + str(x)) print ("List second: " + str(y)) # Take difference of list 1 and list 2 z = difference (x, y) print("Difference of first and second String: " + str(z)) # if lists are equal if not z: print("First and Second list are Equal") # if lsts are not equal else: print("First and Second list are Not Equal")
Top answer 1 of 4
8
Convert b to a set and then loop over a's items and check if they exist in that set:
>>> s = set(b)
>>> [x for x in a if x in s]
['a', 'd']
2 of 4
3
you need to use set:
>>> a = ['a','s','d','f']
>>> b = ['e','d','y','a','t','v']
>>> sorted(set(a) & set(b), key=a.index) # here sorting is done on the index of a
['a', 'd']
Reddit
reddit.com › r/learnpython › how to best compare two lists using a for loop?
r/learnpython on Reddit: how to best compare two lists using a for loop?
August 17, 2022 -
The task is to take two lists and print the index of every value that matches using a for loop.
a = [0,1,2,3,4,6,4,5,8]
b = [0,5,6,7,4,6,3,5,8]
newlist = []
for number in a:
if number == b[number]:
newlist.append(b.index(number))
print(newlist)The output should be: 0,4,5,8
The output is: 0,4,4,8
After some research I found a lot of better ways of doing this exercise (list comprehensions etc.) . I can not figure out though what the mistake is in this example. I already tried variations of this using range() - for number in range(len a)
What am I missing here?
Edit: sry - I meant the output should be 0,4,5,7,8
Top answer 1 of 7
11
You're comparing the entry in a (call it x) with the entry at the xth position in b. If you want to go through things stepwise like this, consider using the enumerate function to keep indices consistent. newlist = [] for i, value in enumerate(a): if a[i] == b[i]: newlist.append(i) print(newlist) Here's how that looks as a list comprehension: print([i for i, val in enumerate(a) if a[i] == b[i]])
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eq = [index for index, (x, y) in enumerate(zip(a, b)) if x == y] https://docs.python.org/3/glossary.html#term-list-comprehension https://docs.python.org/3/library/functions.html#enumerate https://docs.python.org/3/library/functions.html#zip
GeeksforGeeks
geeksforgeeks.org › python › python-difference-two-lists
Difference between Two Lists in Python - GeeksforGeeks
November 27, 2025 - Counter subtracts the frequencies, removing elements that appear in both lists and keeping the extra occurrences from the first list. ... from collections import Counter a = [1, 2, 3, 3, 4] b = [3, 4] c = list((Counter(a) - Counter(b)).elements()) print(c) ... Counter(a) creates a frequency map of list a. Counter(a) - Counter(b) subtracts occurrences of matching items. .elements() expands remaining counts back into a list.
Quora
quora.com › How-can-I-do-a-comparison-of-two-lists-in-Python-with-each-value
How to do a comparison of two lists in Python with each value - Quora
Answer (1 of 8): Depends on what you are trying to do, but I am taking it to mean you want to find common numbers: [code]shared_numbers = [] for number in set(reduce(lambda a, b: a+b, map(lambda y: map(lambda x: x, y), a))): if number in set(reduce(lambda a, b: a+b, map(lambda y: map(lambda ...
Reddit
reddit.com › r/pythonlearning › how can i compare two lists and return the positions(?) of not matches
r/PythonLearning on Reddit: How can I compare two lists and return the positions(?) of not matches
December 19, 2024 -
for example if i had
l1 = [ 1,1,1,1,1 ]
l2 = [ 1,0,1,1,0 ]
i would want it to return 2 and 5
Top answer 1 of 2
1
You could do a if statement in a for loop Ex : for I in range (5): If l1[i] != l2[i] : print(i) It would output 1 and 4 since index starts at 0 If for some whatever reason you want 2 and 5 you can do print(I + 1) instead
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Let’s have fun with this one. def index_not_matching(A: list, B: list) -> list[int]: res = [] for index, _a, _b in enumerate(zip(A,B)): if _a != _b: res.append(index) return res Note: list indexes start at 0 in Python. So you would receive 1 and 4 not 2 and 5.
Intellipaat
intellipaat.com › community › 11860 › how-can-i-compare-two-lists-in-python-and-return-matches
How can I compare two lists in python and return matches - Intellipaat Community
July 17, 2019 - I want to take two lists and find the values that appear in both. a = [1, 2, 3, 4, 5] b ... 5] returnMatches(a, b) would return [5], for instance.