python check two lists are equal using a not equal

Question

I am new to the python. I have two lists:

l1 = [1,1,1]
l2 = [1,1,1]

Now, I have to check whether these two are equal or not. I have a solution which I am currently using:

def comp(l1,l2):
    #condition we are checking [1,1,1] and  [1,1,1]
    try:
        a= set(l1)  #converting a list into set , as set will return the length on basis of unique elements.
        b= set(l2)
        return ((a == b) and (len(a) == 1) and (len(b) == 1))
    except TypeError:
        return False

Now, with this I am able to solve the task. But I am trying to do it elementwise.

l1 = [1,1,12]
l2 = [1,1,1]

Then I can treat the 12 as a 1 so I need to know which number is not matching. Can any one help me with this ?

Lists can be compared with `l1 == l2`, it will, behind the curtains, check if the length is the same, and iterate over the elements. You implementations however, will check if the two lists have the same elements, so `[2,1,1]` and `[1,2]` will be the same in your `comp` function. — Willem Van Onsem, Nov 11 '19 at 12:34
There is nothing wrong with that. Actually I am trying to equivalent some data so — ganesh kaspate, Nov 11 '19 at 12:34
Does this answer your question? [How can I compare two lists in python and return matches](https://stackoverflow.com/questions/1388818/how-can-i-compare-two-lists-in-python-and-return-matches) — Divyesh patel, Nov 11 '19 at 12:36
It will be mostly length. either it might be empty or may be 2 elements. but mostly three — ganesh kaspate, Nov 11 '19 at 12:36

score 3 · Accepted Answer · answered Nov 11 '19 at 12:38

3

Assuming they have the same length, you could do:

{i: (v, l2[i]) for i, v in enumerate(l1) if v != l2[i]}

which returns

{2: (12, 1)}

for you example above. The keys are the indices, the values are tuples of the respective values in the lists.

answered Nov 11 '19 at 12:38

Cleb

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How do I check which elements are not matching – ganesh kaspate Nov 11 '19 at 12:41
@GaneshKaspate: As written the keys of this dictionary represent the indices of not-matching elements (here: `2`), and the values are tuples of the values that are different (here: `1` and `12`). – Cleb Nov 11 '19 at 12:43
IndexError: list index out of range .. How do I handle such sistuation – ganesh kaspate Nov 11 '19 at 12:48
I am trying to print this values – ganesh kaspate Nov 11 '19 at 12:53
@GaneshKaspate: then your lists might not have the same length; the above - as written - will only work if they have the same length. – Cleb Nov 11 '19 at 12:59
okays.. So, this is returning the common elements and also the uncommon element like that – ganesh kaspate Nov 11 '19 at 13:01
@GaneshKaspate: No, only the uncommon once are returned (indices and actual values) as desired according to your question. – Cleb Nov 11 '19 at 14:27

score 3 · Answer 2 · answered Nov 11 '19 at 12:40

If you need to know if the two list are exactly the same you can do l1 == l2 directly.

If you need to compare the lists element-wise (assuming they have the same length) and you only play with list of numbers, you can use numpy arrays :

import numpy as np

l1 = np.array([1,1,12])
l2 = np.array([1,1,1])

l1 == l2 # array([ True, True, False])

Aryerez · Answer 3 · 2019-11-11T13:23:55.760

0

Assuming the lists are always the same length, You can do:

is_all_equel = True
for i in range(len(l1)):
    if l1[i] != l2[i]:
        print("index " + str(i) + " is " + str(l1[i]) + " in list 1, and " + str(l2[i]) + " in list 2")
        is_all_equel = False

In is_all_equel will be the answer if all the elements in the lists are equel

edited Nov 11 '19 at 13:23

answered Nov 11 '19 at 12:36

Aryerez

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It might have 2 elements but only one place it may be – ganesh kaspate Nov 11 '19 at 12:37
when will it return true ? – ganesh kaspate Nov 11 '19 at 12:57
this is not returning weather all elements are equal or not – ganesh kaspate Nov 11 '19 at 13:08
What if I have to return a true from this. Then do I have to write an else part and then compare one by one? – ganesh kaspate Nov 12 '19 at 04:40

score 0 · Answer 4 · answered Nov 11 '19 at 12:57

0

something like:

l1 = [1,1,12]
l2 = [1,1,1]
for elem in l1:
    if not elem in l2:
        print(elem)
        print(l1.index(elem))

answered Nov 11 '19 at 12:57

g kexxt

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python check two lists are equal using a not equal

4 Answers4