Writing numbers in file on new lines

Question

I am trying to read one file f1 , it contains numbers like this:

2
5
19
100
34
285
39
12

and I want to read this numbers, square them and write in a new file, each on new line. This is my code:

with open("Data.txt", 'r') as f1, open("Double.txt", 'w') as f2:
    Lines = f1.readlines()
    for new_line in Lines:
        if new_line.isdigit():
            x = int(new_line)
            x = pow(x, 2)
            on_new_line = str(x) + "\n"
            f2.write(on_new_line)

but in second file it writes only

144

Can someone help me with this?

Answer 1

The reason the file is only returning 144 is because using readlines() returns the line as a string, which includes the newline character at the end: \n

We can solve this by reading the file in as a whole and splitting on the newline characters to put the items in an array:

with open('data.txt', 'r') as f1, open('double.txt', 'w') as f2:
    lines = f1.read().split('\n')
    for new_line in lines:
        squared = int(new_line)**2
        f2.write(f"{squared}\n")

This will create an array with each item as a string, so on line 4, we cast that to an int in order to square it.

We also write each element to the new text file, with a newline character after it again.

Answer 2

You can iterate throw the file this way:

path1 = "Data.txt"
path2 = "Double.txt"

with open(path1, 'r') as f1, open(path2, 'w') as f2:
    for line in f1:
        try:
            f2.write(str(int(line)**2))
        except ValueError:
            pass