Python: Reading a file and reverse all lines

Question

So I'm trying to reverse all lines, but instead I get totaly strange reverse, it puts 4th line on the 1st line with the 5 line...

How file looks before reversing:

1 line
2 line
3 line
4 line
5 line

After reversing:

5 line4 line
3 line
2 line
1 line

Here is the code:

 file = open(filename, "r")
 list = file.readlines()
 file.close()
 list.reverse()
 file = open(filename, "w")
 for value in list:
 file.write(value)
 file.close()

• jfs: related: Read a file in reverse order using python. See also reversed_lines() function

Answer 1

It seems that you didn't have the end line sign in the last line (the '\n'). It could be fixed easily by adding '\n' when needed:

file = open(filename, "w")
 for value in list:
 file.write(value.rstrip() + "\n")
 file.close()

• jfs: use with-statement to close the file even if an exception happens: with open(filename, 'w') as file: file.writelines(map(str.rstrip, lines))

Answer 2

Every line of the file has a newline character \n at the end of it, except for the very last line.

The simplest way would be to do this:

file.open(filename,'r')
lines = file.read().split("\n")
file.close()
file = open(filename, "w")
file.write("\n".join(lines[::-1]))
file.close()

You could also try using str.strip() or str.rstrip() to remove all whitespace from the ends of a string or just the right end. This, however, would also remove spaces, tabs, etc.