How to remove final character in a number of strings?

Question

I have a number of strings that I would like to remove the last character of each string. When I try out the code below it removes my second line of string instead of removing the last element. Below is my code:

Code

with open('test.txt') as file:
    seqs=file.read().splitlines()
    seqs=seqs[:-1]

test.txt

ABCABC
XYZXYZ

Output

ABCABC

Desired output

ABCAB
XYZXY

Think about what `seqs` is after the first assignment... It's a list of all *lines* (i.e. a list of strings). You need another loop to modify each line. List comprehension will be your friend in this situation. — Some programmer dude, Jan 12 '16 at 09:39
You are dealing with array of arrays of strings, not arrays of strings — Rocketq, Jan 12 '16 at 09:39

score 10 · Accepted Answer · edited Nov 26 '19 at 05:13

10

Change this seqs=seqs[:-1]

to a list comprehension:

seqs=[val[:-1] for val in seqs]

Note:

The problem in your old method is that seq is a list of strings i.e ["ABCABC","XYZXYZ"]. You are just getting the item before last item ABCABC which explains the output.
What I have done is get the strings from the list and omit it's last character.

edited Nov 26 '19 at 05:13

d e

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answered Jan 12 '16 at 09:41

The6thSense

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Kaustav Datta · Answer 2 · 2016-01-12T09:51:15.107

5

with open('test.txt') as file:
    for seq in file:
        print seq.strip()[:-1]

This iterates through every line in the file and prints the line omitting the last character

edited Jan 12 '16 at 09:51

answered Jan 12 '16 at 09:41

Kaustav Datta

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Your method would be less memory consuming then mine good answer :). – The6thSense Jan 12 '16 at 09:56
1

Rather than `print`, you could also `yield` the value. Then you can write `for value in truncated():` and do further processing on each truncated value. – Martin Bonner supports Monica Jan 12 '16 at 10:18

score 4 · Answer 3 · answered Jan 12 '16 at 09:43

file.read().splitlines() returns a list. Therefore the following could solve your problem:

enter with open('test.txt') as file:
    data = list(map(lambda x: x[:-1], file.read().splitlines()))

Then you can join the list back into a string: "\n".join(data)

score 2 · Answer 4 · edited Jan 12 '16 at 09:44

2

seqs is a list of lines. You need to loop through the lines to access each line:

with open('test.txt') as file:
    seq = file.read().splitlines()
    for word in seq:
        word = word[:-1]
        print word

edited Jan 12 '16 at 09:44

Idos

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answered Jan 12 '16 at 09:41

deborah-digges

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How to remove final character in a number of strings?

4 Answers4