How to while loop until the end of a file in Python without checking for empty line?

Question

I’m writing an assignment to count the number of vowels in a file, currently in my class we have only been using code like this to check for the end of a file:

vowel=0
f=open("filename.txt","r",encoding="utf-8" )
line=f.readline().strip()
while line!="":
    for j in range (len(line)):
        if line[j].isvowel():
            vowel+=1

    line=f.readline().strip()

But this time for our assignment the input file given by our professor is an entire essay, so there are several blank lines throughout the text to separate paragraphs and whatnot, meaning my current code would only count until the first blank line.

Is there any way to check if my file has reached its end other than checking for if the line is blank? Preferably in a similar fashion that I have my code in currently, where it checks for something every single iteration of the while loop

Thanks in advance

Asked By: ay lmao

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Source

Answer 1

Don’t loop through a file this way. Instead use a for loop.

for line in f:
    vowel += sum(ch.isvowel() for ch in line)

In fact your whole program is just:

VOWELS = {'A','E','I','O','U','a','e','i','o','u'}
# I'm assuming this is what isvowel checks, unless you're doing something
# fancy to check if 'y' is a vowel
with open('filename.txt') as f:
    vowel = sum(ch in VOWELS for line in f for ch in line.strip())

That said, if you really want to keep using a while loop for some misguided reason:

while True:
    line = f.readline().strip()
    if line == '':
        # either end of file or just a blank line.....
        # we'll assume EOF, because we don't have a choice with the while loop!
        break

Answered By: Adam Smith

Answer 2

I discovered while following the above suggestions that
for line in f:
does not work for a pandas dataframe (not that anyone said it would)
because the end of file in a dataframe is the last column, not the last row.
for example if you have a data frame with 3 fields (columns) and 9 records (rows), the for loop will stop after the 3rd iteration, not after the 9th iteration.
Teresa

Answered By: Teresa Aysan

Answer 3

Find end position of file:

f = open("file.txt","r")
f.seek(0,2) #Jumps to the end
f.tell()    #Give you the end location (characters from start)
f.seek(0)   #Jump to the beginning of the file again

Then you can to:

if line == '' and f.tell() == endLocation:
   break

Answered By: Punnerud

Answer 4

import io

f = io.open('testfile.txt', 'r')
line = f.readline()
while line != '':
        print line
        line = f.readline()
f.close()

Answered By: LanderSage

How to while loop until the end of a file in Python without checking for empty line?

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