printing lines from a file within an inclusive alphabetical range not including desired limits

Question

The trouble I'm having with this program is that it is not including the bounds even though I use the >= <= operators. Also for some reason the words that are output are each separated by a newline rather than printing one after another.

For example, if the chosen .txt file contains:

Aladdin
Batman
Dinosaurs
Edgar
Fruitloop
Mongoose

and the chosen upper and lower bounds are:

Batman
Fruitloop

The program prints:

Batman

Dinosaurs

Edgar

Here is what I'm working with. Any help is greatly appreciated!

import os

user_file = input() #reads name of user chosen .txt file containing alphabetized one word per line lists
lo_limit = input() #reads a user chosen word as the inclusive lower alphabetical limit
up_limit = input() #reads a user chosen word as the inclusive upper alphabetical limit

file_handle = open(user_file) #opens user chosen file

lines = file_handle.readlines() #creates by-line string of file contents


#if user chosen file contains words equal to or between bounds, prints words
for ln in lines:
    if ln >= lo_limit \
        and ln <= up_limit:
        print(ln)

thekid77777 · Answer 1 · 2020-06-21T04:35:13.413

Ok starting with how your opening the file, its easier to open it with a context manager like this, then it handles the opening/closing for you.

with open('input.txt') as f:
    lines = f.readlines()

On to why your code isn't working, you have to consider what file_handle.readlines() is doing and storing. I believe you are under the impression that lines contains:

['Aladdin', 'Batman', 'Dinosaurs', 'Edgar', 'Fruitloop', 'Mongoose']

when in reality it contains:

['Aladdin\n', 'Batman\n', 'Dinosaurs\n', 'Edgar\n', 'Fruitloop\n', 'Mongoose']

You can use a list comprehension like so to peel that newline escape character off:

lines = [l.replace('\n', '') for l in lines]

Then your logic should work fine. In summary, try something like this:

with open('input.txt') as f:
    lines = f.readlines()

lines = [l.replace('\n', '') for l in lines]

print(lines)

lo_limit = 'Batman'
up_limit = 'Fruitloop'

for ln in lines:
    if ln >= lo_limit and ln <= up_limit:
        print(ln)

which gives output:

['Aladdin', 'Batman', 'Dinosaurs', 'Edgar', 'Fruitloop', 'Mongoose']
Batman
Dinosaurs
Edgar
Fruitloop

Kind of confused, how does this deserve a downvote? I showed and explained why it wasn't working, offered a suggestion for file i/o as he never closes the file, and showed him how to adjust the array he reads in so that it will work with his logic. Would like an explanation on this downvote please. — thekid77777, Jun 21 '20 at 04:32

score 1 · Answer 2 · answered Jun 21 '20 at 03:44

This is not how to select a range of lines. This case is working because the input is ascending order. Give it a random input and you'll not get what you expect.

lines = """Aladdin
Batman
Dinosaurs
Edgar
Axe # input to break the ascending order
Fruitloop
Mongoose"""

lines = lines.split("\n")

for i in range(len(lines)):
    if "Batman" == lines[i]:
        for j in range(i, len(lines)):
            print(lines[j])
            if "Fruitloop" == lines[j]:
                break

To get a range of lines, you first need to loop on the lines, find the starting line, then start looping from that line until you find the ending line.

Also: Always use a with clause to open a file:

with open(file, "r") as file:
    for line in file:
        # read line by line here

MrNobody33 · Accepted Answer · 2020-06-21T04:24:49.357

That happens because when you do f.readlines() this will return a list like this:

f.readlines()
>>>['Aladdin\n', 'Batman\n', 'Dinosaurs\n', 'Edgar\n', 'Fruitloop\n', 'Mongoose']

And when you enter up_limit=Edgar, you will be comparing each of the list f.readlines() with the word Edgar like this:

'Aladdin\n'>=lo_limit and 'Aladdin\n'<='Edgar'
>>>True
'Batman\n'>=lo_limit and ''Batman\n''<='Edgar'
>>>True
....
....
....

And when becomes the iteration of 'Edgar\n' you can check that:

'Edgar'>='Edgar\n'
Out[6]: False

And that's why 'Edgar' is not printed. You could try:

import os

user_file = input() #reads name of user chosen .txt file containing alphabetized one word per line lists
lo_limit = input() #reads a user chosen word as the inclusive lower alphabetical limit
up_limit = input() #reads a user chosen word as the inclusive upper alphabetical limit

with open(str(user_file)) as file_handle:#opens user chosen file
    lines = file_handle.readlines()
    #if user chosen file contains words equal to or between bounds, prints words
    for ln in lines:
        if (ln > lo_limit) or (ln == lo_limit) or (ln < up_limit):
            print(ln)
            if (ln == up_limit+'\n'):
                break

Or you can select by index:

user_file = input() #reads name of user chosen .txt file containing alphabetized one word per line lists
lo_limit = str(input()) #reads a user chosen word as the inclusive lower alphabetical limit
up_limit = str(input()) #reads a user chosen word as the inclusive upper alphabetical limit

with open(str(user_file)) as file_handle:#opens user chosen file
    lines = file_handle.readlines() #creates by-line string of file contents    
    linesselected=lines[lines.index(lo_limit+'\n'):(lines.index(up_limit+'\n')+1)]
    for i in linesselected:
        print(i.replace('\n',''))

score 0 · Answer 4 · answered Jun 21 '20 at 04:06

You need to replace ">=" and "<=" with ">" and "<". Also remove "\n" from each line.

To leave the result on the same line you need to use the end attribute of the print function.

Stays like this:

user_file = input() #reads name of user chosen .txt file containing alphabetized one word per line lists
lo_limit = input() #reads a user chosen word as the inclusive lower alphabetical limit
up_limit = input() #reads a user chosen word as the inclusive upper alphabetical limit

file_handle = open(user_file) #opens user chosen file

lines = file_handle.readlines() #creates by-line string of file contents

#if user chosen file contains words equal to or between bounds, prints words
for ln in lines:
    ln = ln.replace('\n', '')
    if ln > lo_limit \
        and ln < up_limit:
        print(ln, end=' ')

output:

$ python file.py 
arquivo.txt
Aladdin
Mongoose
Batman Dinosaurs Edgar Fruitloop

printing lines from a file within an inclusive alphabetical range not including desired limits

4 Answers4