Python - remove empty lines of text at the end of a file

Question

I am writing a script that modifies any text files. It replaces white spaces with blank lines. It erases empty lines at the end of the file. The image shows the result I want.

I can get closer to the desired result. The problem is that I cannot get rid of the last empty line. I think this has something to do with the last line. for example, ' the lines below me should be gone looks like this: ' the lines below me should be gone\n' It seems that new lines are created in the previous line. for example, if line 4 has \n than line 5, it will actually be an empty line, not line 4.

I should note that I cannot use rstrip or strip

My code is still.

 def clean_file(filename): # function to check if the line can be deleted def is_all_whitespace(line): for char in line: if char != ' ' and char != '\n': return False return True # generates the new lines with open(filename, 'r') as file: file_out = [] for line in file: if is_all_whitespace(line): line = '\n' file_out.append(line) # removes whitespaces at the end of file while file_out[-1] == '\n': # while the last item in lst is blank file_out.pop(-1) # removes last element # writes the new the output to file with open(filename, 'w') as file: file.write(''.join(file_out)) clean_file('test.txt') 

Answer 1

\n essentially means "create another line"

So, when you deleted all lines \n , there is still the previous line

 the lines below me should be gone\n 

Which again means “create another line”, beyond the ones you have already deleted

Since you say you cannot use rstrip , you can end the loop with

 file_out[-1] = file_out[-1].strip('\n') 

remove \n from the last item. Since \n cannot exist anywhere on the line, rstrip and strip will have the same effect

Or without any strip or endswith :

 if file_out[-1][-1] == '\n': file_out[-1] = file_out[-1][:-1] 

Note that \n is a single character, serial number 0x0a as hexadecimal, not two characters \ and n , ordinals 0x5c and 0x6e . That's why we use -1 , not -2