How to count the precise line number in a file with python?

Question

This is the code I use to count lines in a file. I don't think it is wrong. But why the result is always one line more than I check directly using gedit ? I can just minus 1 to get the right result but I want to know why.

        file = open(filename)
        allLines = file.read()
        file.close()
        Lines=allLines.split('\n')
        lineCount = len(Lines)

And reading the entire file at a time is not very efficient. — thefourtheye, Apr 05 '14 at 12:51
what output do you get if you do `Lines = allLines.splitlines()` — shx2, Apr 05 '14 at 12:51
Here are several other ways by the way: http://stackoverflow.com/questions/845058/how-to-get-line-count-cheaply-in-python — Aeveus, Apr 05 '14 at 12:53
Thx,I think I have known. About the semi colons,sorry just forgot to delete — hidemyname, Apr 05 '14 at 12:54
First, if you check a script, they ALL have a last line (blank) for interpreters: it is the ctrl-z/d that you use from CLI. Second, use an incremental reader: you don't know how large the file is. I teach my lesson after I try to read an 8Gb iso with sh extension on my old pocket PC with 256 Mb RAM... — cox, Apr 05 '14 at 12:56

score 2 · Answer 1 · answered Apr 05 '14 at 12:57

2

Here is the memory-efficient and pythonic way to iterate through the file and count its lines (separated with \n).

with open(filename) as file:
    lines_count = sum(1 for line in file)

answered Apr 05 '14 at 12:57

Ivan Klass

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score 0 · Answer 2 · answered May 02 '20 at 13:57

0

Try this :

file_handle = open('filename.txt', 'r')
newlines=len(file_handle.readlines())
print('There are %d lines in the file.' % (newlines))

answered May 02 '20 at 13:57

efdummy

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How to count the precise line number in a file with python?

2 Answers2