for loop doesn't loop to next element python

Question

I am trying to loop through a list. But it is getting the first element. It doesn't gets the second element. I can't figure out what i am doing wrong.

filte = ['fingerprint','cipher']
dupe = ['cipher','extract']

for val in filte:
    print(val)
    if val in dupe:
        dupe.remove(val)
    else:
        filte.remove(val)

print("filter",filte)
print("dupe",dupe)

output i got:

fingerprint
filter ['cipher']
dupe ['cipher', 'extract']

required output:

fingerprint
cipher
filter ['cipher']
dupe [ 'extract']

I don't exactly know how loops work in Python, but as you are removing an element during the loop, it mays bring an iterating issue. It's waiting for a second element, but after removing, cipher becomes the first one, so there is no second. — Kévin Bibollet
– Kévin Bibollet, Commented May 14, 2019 at 8:07
Exactly. So OP you want to either iterate on a reversed list (deleting its last element does not alter its indexes) or build a new list where you append the element that are suitable. — Guimoute
– Guimoute, Commented May 14, 2019 at 8:11
Could you explain @SmackAlpha what are you trying to do here? — Devesh Kumar Singh
– Devesh Kumar Singh, Commented May 14, 2019 at 8:24

Rakesh · Accepted Answer · 2019-05-14 08:09:51Z

3

Use set

Ex:

filte = ['fingerprint','cipher']
dupe = ['cipher','extract']

print(list(set(filte) - set(dupe)))  #OR list(set(filte).difference(set(dupe)))
print(list(set(dupe) - set(filte)))

Output:

['fingerprint']
['extract']

Note: Not a good practice to remove elements while iterating the object.

answered May 14, 2019 at 8:09

Rakesh

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Comments

umn · Accepted Answer · 2019-05-14 08:08:52Z

0

just remove the else

filte = ['fingerprint','cipher']
dupe = ['cipher','extract']

for val in filte:
    print(val)
    if val in dupe:
        dupe.remove(val)
        filte.remove(val)

print("filter",filte)
print("dupe",dupe)

output:

fingerprint
cipher
filter ['fingerprint']
dupe ['extract']

answered May 14, 2019 at 8:08

umn

4816 silver badges18 bronze badges

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