How to get a line count of a file in Python

Question

I am trying to get a line count of a file using command prompt. However when I execute the code I get the output of 0.

import sys
file = open(sys.argv[1],"r")
lines=0
line=file.readline()
while line !="":
  lines=lines+1
  line=file.readline()
print("Lines:"+str(lines)+"\n")
file.close()

This code works perfectly fine, the lines inside the file was deleted.And that caused the output of 0

Does this answer your question? [How to get line count of a large file cheaply in Python?](https://stackoverflow.com/questions/845058/how-to-get-line-count-of-a-large-file-cheaply-in-python) — sudonym, Nov 17 '20 at 02:57
The code works, but [as the OP mentioned in the comments](https://stackoverflow.com/questions/64868567/how-to-get-a-line-count-of-a-file-in-python#comment114688506_64868694), the "*lines inside the data is deleted*". — Gino Mempin, Nov 17 '20 at 05:27

score 1 · Accepted Answer · answered Nov 17 '20 at 02:58

1

import sys
file = sys.argv[1]

with open(file, "r") as f:
    num_lines = len(f.readlines())

answered Nov 17 '20 at 02:58

Antimon

597
3
10

It returns me a value of 0 – babybirkins Nov 17 '20 at 03:10
Double check your file and that your script picks up the right argument from argv. – Antimon Nov 17 '20 at 03:11
1

Thank you! You were right I found out that the lines inside the data is deleted. – babybirkins Nov 17 '20 at 03:19
Sometimes it's the stupidest things that trip you up. :) – Antimon Nov 17 '20 at 03:22

score 0 · Answer 2 · answered Nov 17 '20 at 02:49

0

I think you want readlines not readline

answered Nov 17 '20 at 02:49

Kenan

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score 0 · Answer 3 · answered Nov 17 '20 at 02:52

0

import sys
file = open(sys.argv[1],"r")
lines = file.readlines()
file.close()
line_count = len(lines)
print(f"There are {line_count} lines")

answered Nov 17 '20 at 02:52

Epic Gamer

101
1
10

I get 0 when I use this code – babybirkins Nov 17 '20 at 03:04

sudonym · Answer 4 · 2020-11-17T03:10:33.223

0

to get your line count, try this:

import sys, os

def file_len(fname):
    if os.stat(file_path).st_size == 0:
        print('File is empty')
        return 0
    with open(fname) as f:
        for i, l in enumerate(f):
            pass
    return i + 1

print(file_len(sys.argv[1]))

edited Nov 17 '20 at 03:10

answered Nov 17 '20 at 02:56

sudonym

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no :( good catch – sudonym Nov 17 '20 at 03:07

Matthias Fripp · Answer 5 · 2020-11-17T03:14:00.493

0

Your code runs fine for me if I run it as python myscript.py myfile.txt, using Python 3.8.5 on MacOS.

However the script could be cleaned up a little. It would be a good idea to use Python's open() context handler while reading the file, the readlines() method to get all the lines at once, and Python's built-in tools for string formatting. Then you can do the whole count very simply like this:

import sys
with open(sys.argv[1]) as file:
    lines = len(file.readlines())
print(f"Lines: {lines}\n")

You may also want to consider using Python's argparse module to handle your argument(s).

edited Nov 17 '20 at 03:14

answered Nov 17 '20 at 02:59

Matthias Fripp

17,670
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It gives me the following error: IndexError: list index out of range – babybirkins Nov 17 '20 at 03:06
Yeah, I was mistaken about the order of arguments in an early version of this answer. Turns out your code runs fine for me as-is. Are you sure you're not specifying an empty file? – Matthias Fripp Nov 17 '20 at 03:07

How to get a line count of a file in Python

5 Answers5