Python - For Loop - Print only if the above line is equal

Question

I've the following code:

characters = ['a', 'b', 'b', 'c','d', 'b']

for i in characters:
    if i[0] == i[-1]:
        print(i)

Basically I only want to extract the characters that are equal from the line above. For example, in my case I only want to extract the b from 1 and 2 position.

How can I do that?

Thanks!

Possible duplicate of [Identify if list has consecutive elements that are equal in python](https://stackoverflow.com/questions/38708692/identify-if-list-has-consecutive-elements-that-are-equal-in-python) — Rahul Agarwal, Sep 18 '18 at 10:40

score 1 · Answer 1 · answered Sep 18 '18 at 10:41

1

a = ['a', 'b', 'b', 'c', 'd', 'b']
b = ['a', 'b', 'b', 'c', 'd', 'b', 'd']

import collections

print([item for item, count in collections.Counter(a).items() if count > 1])
print([item for item, count in collections.Counter(b).items() if count > 1])

output

['b']
['b', 'd']

answered Sep 18 '18 at 10:41

Nihal

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he wants the one that is equal to the last one not the ones repeated, how could someone upvote this? – E.Serra Sep 18 '18 at 10:46

score 1 · Answer 2 · answered Sep 18 '18 at 10:42

1

Without iterating multiple times over the same list.

characters = ['a', 'b', 'b', 'c','d', 'b']
last_char = None

output = []

for char in characters:
    if char == last_char:
        output.append(char)
    last_char = char

print(output)

answered Sep 18 '18 at 10:42

Tom Wojcik

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score 0 · Accepted Answer · edited Sep 18 '18 at 10:54

To extract the characters form the list which matches only the last char from list you can do the following:

characters = ['a', 'b', 'b', 'c','d', 'b']

for i in range(0, len(characters) - 1):
    if characters[i] == characters[-1]:
        print(characters[i])

In you snippet i when you are looping is the individual chars from your list, and it looks you were trying to access last, and first item from the list.

score 0 · Answer 4 · answered Sep 18 '18 at 10:42

0

equal = [a for a in characters[0:-1] if a == characters[-1]]

Unless you also want the last character which will always be equal to itself, then do:

equal = [a for a in characters if a == characters[-1]]

answered Sep 18 '18 at 10:42

E.Serra

1,495
11
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score 0 · Answer 5 · answered Sep 18 '18 at 10:54

0

little modification in your code

characters = ['a', 'b', 'b', 'c','d', 'b']
ch=  (characters[-1])
for i in characters:
    if i == ch:
        print(i

answered Sep 18 '18 at 10:54

Roshan Bagdiya

2,048
21
41

Python - For Loop - Print only if the above line is equal

5 Answers5