I want to append a newline to my string every time I call file.write(). What’s the easiest way to do this in Python?

Use “\n”:

file.write("My String\n")

See the Python manual for reference.

You can do this in two ways:

f.write("text to write\n")

or, depending on your Python version (2 or 3):

print >>f, "text to write"         # Python 2.x
print("text to write", file=f)     # Python 3.x

You can use:

file.write(your_string + '\n')

If you use it extensively (a lot of written lines), you can subclass ‘file’:

class cfile(file):
    #subclass file to have a more convienient use of writeline
    def __init__(self, name, mode = 'r'):
        self = file.__init__(self, name, mode)

    def wl(self, string):
        self.writelines(string + '\n')

Now it offers an additional function wl that does what you want:

fid = cfile('filename.txt', 'w')
fid.wl('appends newline charachter')
fid.wl('is written on a new line')
fid.close()

Maybe I am missing something like different newline characters (\n, \r, …) or that the last line is also terminated with a newline, but it works for me.

you could do:

file.write(your_string + '\n')

as suggested by another answer, but why using string concatenation (slow, error-prone) when you can call file.write twice:

file.write(your_string)
file.write("\n")

note that writes are buffered so it amounts to the same thing.

file_path = "/path/to/yourfile.txt"
with open(file_path, 'a') as file:
    file.write("This will be added to the next line\n")

or

log_file = open('log.txt', 'a')
log_file.write("This will be added to the next line\n")

Just a note, file isn’t supported in Python 3 and was removed. You can do the same with the open built-in function.

f = open('test.txt', 'w')
f.write('test\n')

Unless write to binary files, use print. Below example good for formatting csv files:

def write_row(file_, *columns):
    print(*columns, sep='\t', end='\n', file=file_)

Usage:

PHI = 45
with open('file.csv', 'a+') as f:
    write_row(f, 'header', 'phi:', PHI, 'serie no. 2')
    write_row(f)  # newline
    write_row(f, data[0], data[1])

Notes:

• print documentation
• '{}, {}'.format(1, 'the_second') – https://pyformat.info/, PEP-3101
• ‘\t’ – tab character
• *columns in function definition – dispatches any number of arguments to list – see question on *args & **kwargs

Another solution that writes from a list using fstring

lines = ['hello','world']
with open('filename.txt', "w") as fhandle:
  for line in lines:
    fhandle.write(f'{line}\n')

This is the solution that I came up with trying to solve this problem for myself in order to systematically produce \n’s as separators. It writes using a list of strings where each string is one line of the file, however it seems that it may work for you as well. (Python 3.+)

#Takes a list of strings and prints it to a file.
def writeFile(file, strList):
    line = 0
    lines = []
    while line < len(strList):
        lines.append(cheekyNew(line) + strList[line])
        line += 1
    file = open(file, "w")
    file.writelines(lines)
    file.close()

#Returns "\n" if the int entered isn't zero, otherwise "".
def cheekyNew(line):
    if line != 0:
        return "\n"
    return ""