Adding line numbers to the output in Python

Question

For example, if the input file is:

def main():
    for i in range(10):
        print("I love Python")
    print("Good bye!")

Answer 1

Use a with statement to close the file buffer and just concatenate strings:

with open('file.txt', 'r') as program:
    data = program.readlines()

with open('file.txt', 'w') as program:
    for (number, line) in enumerate(data):
        program.write('%d  %s' % (number + 1, line))

Answer 2

You should add:

newFile = open(yourfile, 'w')
count = 1

for line in readfile:
    newFile.write (str(count) + '\t' + line)
    count += 1
newFile.close()

If you just want to print to console write (this is according to the variable names you've used in your second edit):

for lines in openfile:
    print str(count) + '\t' + lines
    count += 1

You should do your homework yourself, though!

Answer 3

I would write so:

with open(path) as src:
    for index, line in enumerate(src.readlines(), start=1):
        print '{:4d}: {}'.format(index, line.rstrip())

or

with open(path) as src:
    print '\n'.join(['{:4d}: {}'.format(i, x.rstrip()) for i, x in enumerate(src.readlines(), start=1)])