What is the output of print(sum(1 for line in open("filename.txt"))) ?

Question

It exactly gives the number of lines present in the file. I don't know how it works. Can anyone help me...

Answer 1

well, that's an approximate explanation ^^

no tuple used here, but list comprehension syntax wich makes a generator passed as argument to sum() function...

the list comprehension iterate over the opened file wich give each lines in it, and return 1 for each line, so sum of 1 times number of lines in file give total number of lines ^^

open() doesn't "return a list of lines in a file", but return a file object that will be iterated line by line...

to get a list of lines in a file, you should use readlines() function on it:

lineslist = open("filename.txt").readlines()

so you could get total number of lines in a file by doing:

print(len(open("filename.txt").readlines()))

Answer 2

˜”*°•.˜”*°• Mohan 333 •°*”˜.•°*”˜
Thank you

Answer 3

Pardha Saradhi
Here, you seeing tuple comprehension.
open() function has used to open a file.
So,this code open a file and every line of a file 'for' adds one to the tuple.
So,
It looks like this,
sum(1,1,1,1....) #Here 1 means one line

And , sum() function has calculate sum of all ones (lines).

Answer 4

˜”*°•.˜”*°• Mohan 333 •°*”˜.•°*”˜
How 1 is added as tuple by using for loop ? Why don't it take each character instead of each line in the file ?

Answer 5

Pardha Saradhi
Tuple comprehension syntax:

(Expression for counter_variable in iterators (strings,lists,tuples,etc))

In this code we didn't add any expressions just adding 1 only to a tuple.

List comprehensions are also same as a tuple
comprehension. So, have a look on this lesson,

https://www.sololearn.com/learn/JUMP_LINK__&&__Python__&&__JUMP_LINK/2454/

https://www.sololearn.com/learn/Python/2446/

"""
Python has automatically read a file line by line. And open() function return a list of lines in a file.

"""