blank lines in file after sorting content of a text file in python

Question

I have this small script that sorts the content of a text file

# The built-in function `open` opens a file and returns a file object.

# Read mode opens a file for reading only.
try:
    f = open("tracks.txt", "r")


    try:
        # Read the entire contents of a file at once.
       # string = f.read() 
        # OR read one line at a time.
        #line = f.readline()
        # OR read all the lines into a list.
        lines = f.readlines()
        lines.sort()
        f.close()
        f = open('tracks.txt', 'w')
        f.writelines(lines) # Write a sequence of strings to a file
    finally:
        f.close()
except IOError:
    pass

the only problem is that the text is displayed at the bottom of the text file everytime it's sortened...

I assume it also sorts the blank lines...anybody knows why?

and maybe can you suggest some tips on how to avoid this happening?

thanks in advance

Answer 1

An "empty" line read from a text file is represented in Python by a string containing only a newline ("\n"). You may also want to avoid lines whose "data" consists only of spaces, tabs, etc ("whitespace"). The str.strip() method lets you detect both cases (a newline is whitespace).

f = open("tracks.txt", "r")
# omit empty lines and lines containing only whitespace
lines = [line for line in f if line.strip()]
f.close()
lines.sort()
# now write the output file