text - 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!")

Then the output would be:

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

I have difficulty in adding lines to each line. My program is:

filename = input("Please enter a file name: ")
count = 0

openfile = open(filename, "r")

for lines in openfile:
    linenumbers = openfile.write(str(count)+''+lines)
    count += 1

print(count)

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))