CODEWITHSUNDEEP
pythonfor-loop
No this is Patrick
No this is Patrick

Reputation: 157

Appending strings to a list in for loop

Say I have a text file like that where every new letter starts on a new line:

-.H
-.e
-.l
-.l
-.o

I would like to write a code to remove some data from each text line (in the case of example I would like to remove '-.' in front of each letter) and then concatenate the result back together to form:

Hello

What would be a general approach to this kind of problem? I thought it could be solved in a following way:

f = open('hello.txt', 'r')
logs = f.readlines()
f.close()
loglist = list(map(str.strip, logs))
newlist = []

for i in range (len(loglist)):
    splitLetter = loglist[i].split('.')
    letter = splitLetter[-1]
    newlist.append(letter)
    word = ''.join(newlist)
    print word

The problem though is that the result is a series of iterations:

H
He
Hel
Hell
Hello

I need only the last result. How do I get that?

Upvotes: 3

Views: 1638

Answers (6)

Blockost
Blockost

Reputation: 563

Using with ... as statement frees you from closing the file. It will be automatically closed at the end of the block.

Then, in one single line: word = ''.join([l.strip()[-1]] for l in logs)

You don't need to split the string if you strip the string before. You can be sure the letter will be at the last index.

Full code:

with open('hello.txt', 'r') as logs:
    word = ''.join([l.strip()[-1]] for l in logs)
print word

Upvotes: 0

Kevin Rajan
Kevin Rajan

Reputation: 825

The problem with your current code is that you are printing after every iteration. By moving the print statement outside of the for-loop it will print only the last iteration.

f = open('hello.txt', 'r')
logs = f.readlines()
f.close()
loglist = list(map(str.strip, logs))

word = ''.join(l.split('.')[-1] for l in loglist)
print word

Just to make sure this works, I tested it out with a test file with the following text:

-.G
-.o
-.o
-.d
-.b
-.y
-.e

and got the following result:

Goodbye

Upvotes: 1

Daniel
Daniel

Reputation: 42748

You are printing the result in every step. Simply print after the for loop.

You can use generator expressions for shorter program:

with open('hello.txt') as logs:
    word = ''.join(l.strip().split('.')[-1] for l in logs)
print word

Upvotes: 0

Błotosmętek
Błotosmętek

Reputation: 12927

word = ''.join([ l.split('.')[-1] for l in loglist ])

instead of the whole for loop should do.

Upvotes: 0

gopiariv
gopiariv

Reputation: 494

for i in range (len(loglist)):
    splitLetter = loglist[i].split('.')
    letter = splitLetter[-1]
    newlist.append(letter)
word = ''.join(newlist)
print word

or 

word = ''
for i in range (len(loglist)):
    splitLetter = loglist[i].split('.')
    letter = splitLetter[-1]
    word += letter
print word

Upvotes: 0

Carcigenicate
Carcigenicate

Reputation: 45726

Just move the printing outside of the loop:

for i in range (len(loglist)):
    splitLetter = loglist[i].split('.')
    letter = splitLetter[-1]
    newlist.append(letter)

word = ''.join(newlist)
print word

Upvotes: 0

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