Why can't I read a line from a file and print it?

Question

I have the following code:

test_file = open("test.txt","r")
line1 = test_file.readline(1)
test_file.close()
line1 = int(line1)
print(line1)

I have 12 written into the file.

I simply get the output 1.

Can someone please explain what is wrong with this code?

If I had more lines in the file and I only wanted to read the first one, how would I do that? — francisco, Sep 24 '19 at 08:33
@francisco, you are not using any loops so you are just reading the first line — CodeRed, Sep 24 '19 at 08:34
call `readline` multiple times. Or loop over `test_file.readlines()`, which basically does the same thing internally, call `readline` multiple times (I guess). — Vaibhav Vishal, Sep 24 '19 at 08:36
please read the manual for a function if you have a question about a specific function's behaviour. please do this before posting here. — hek2mgl, Sep 24 '19 at 08:38
The parameter to ``readline`` indicates how many characters to read. You literally told it to only read the first character -- i.e. ``1``. — MisterMiyagi, Sep 24 '19 at 08:41
This question has already been answered [here](https://stackoverflow.com/questions/2081836/reading-specific-lines-only). — Marius Mucenicu, Sep 24 '19 at 09:19

score 2 · Answer 1 · answered Sep 24 '19 at 08:32

2

The function readline() has no parameter for reading a special line. It reads from the file line-by-line for each call. To read just the first line call the function one time like:

line1 = test_file.readline()

answered Sep 24 '19 at 08:32

micharaze

957
8
25

You can call it in a `for` loop and increment an index. When the index is reached a specific number you have the specific line you want. – micharaze Sep 24 '19 at 08:40

Saleem Ali · Answer 2 · 2019-09-24T08:39:49.567

1

You have passed the size to read in your code. It read the bytes accordingly to passed size in readline method

Also use with to open file (in pythonic way)

with open("test.txt","r") as test_file:
    line1 = test_file.readline()
    line1 = int(line1)
print(line1)

edited Sep 24 '19 at 08:39

answered Sep 24 '19 at 08:34

Saleem Ali

1,363
11
21

score 0 · Answer 3 · answered Sep 24 '19 at 08:45

When you specify 1, you are telling readline() to take only the first character in your line, it's better to do this update on your code:

test_file = open("test.txt","r")
line1 = test_file.readline() # Remove the indice 1
test_file.close()
line1 = int(line1)
print(line1)

Or in one line like this:

print(int(open("test.txt","r").readline()))

Why can't I read a line from a file and print it?

3 Answers3